# 1200mA HIGH QUALITY Li-Ion charger discussion thread.



## VanIsleDSM (Jun 6, 2008)

I see my original thread was closed. I was just trying to gauge interest, and I thought there would be no better place to gauge interest of electronics than the electronics forum, I didn't mean for my thread to look like a FS ad, sorry for that. Just thought I would keep it all in 1. From now on this thread can be the ongoing discussion about my progress and such. I'll start a thread in the Marketplace with the list of people who want one as soon as I can (I just registered for the Marketplace, but I got no confirmation email, so need to work that out first)

For those who want to see the original thread, it's here:

https://www.candlepowerforums.com/threads/199573

Or if you don't want to bother I'll give you the summary. I'm building my own charger that will hold anything from 18650s to 16340s (34mm to 70mm long, 10 to 21mm wide) seen here:












Max charge current of 1200mA, adjustable down to 1000, 750, 500, 250, and 100mA.

Each battery bay is completely separate from one another and controlled by it's own electronics.

Charges to 4.2V within 0.5%

Preconditions deeply depleted cells.

Automatic end of charge, battery monitoring, and automatic recharge.

Continuous temperature monitoring of each and every cell.

Here's the datasheet for the IC I'll be using for the charger.
http://ww1.microchip.com/downloads/e...doc/21893c.pdf 0.11751955



My first update in this thread is that the electronics were ordered last night, they shipped this morning and they should be here by Monday.

I'm just designing the PCB right now. Stay tuned!


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## Rommul (Jun 6, 2008)

Why aren't the holders wide enough to hold Emoli 26700 as well as AW C Cells?


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## 3rdrock (Jun 6, 2008)




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## VanIsleDSM (Jun 7, 2008)

Rommul said:


> Why aren't the holders wide enough to hold Emoli 26700 as well as AW C Cells?



That's a funny way to make a suggestion.

Nobody has mentioned it yet.. I think if I was making a charger specifically for those batteries, I would probably be looking for something with a 2A charge rate. It would ad quite a bit to the cost of the battery holder if I made it big enough to accept those cells.. although I could look into another holder design that would be slightly more expensive if there was enough interest do it.

The marketplace thread is now open, you can find it here:

http://www.cpfmarketplace.com/mp/showthread.php?t=179626


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## DM51 (Jun 7, 2008)

VanIsleDSM said:


> The marketplace thread is now open...


I will therefore close this one and the discussion can continue there.

Edit: Following submissions received, I am reopening this thread. 

Would the OP and members please note that all SALES discussions mnust take place in the MarketPlace, not here; and that DESIGN issues, including SAFETY considerations, should now take place here.


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## cy (Jun 8, 2008)

let me get this correct... you don't own any li-ion cells... yet you are building a li-ion charger to sell. 

have you done this before? 



VanIsleDSM said:


> As for my testing, I'm wondering if someone has a Li-Ion cell they could donate to the cause. I actually don't have any of my own..



http://www.cpfmarketplace.com/mp/showthread.php?t=179626


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## adamlau (Jun 8, 2008)

Are you still looking for 18650 test cells?


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## cy (Jun 8, 2008)

have you looked a Pila chargers? New style Pila chargers are very high quality and properly terminates a charge and reasonably priced. 

there's a number of reasonably priced quality li-ion chargers, including multi-channels available... 

don't want to insult you but .... your comments indicate that you have little to no experience with li-ion usage, including charging li-ion cells. 

please correct if this is not the case...



VanIsleDSM said:


> Being unsatisfied with chargers on the market, I took it upon myself to make my own.





VanIsleDSM said:


> There's also a safety timer for the whole operation. But I'm not too certain what to set it to yet. at 1200mA how long will it take to charge an 18650? 3 hours, maybe 4? maybe I'll set the safety to around 5 hours, what do you battery gurus think of that?


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## VanIsleDSM (Jun 8, 2008)

cy, you are correct.

However I don't need any experience with Li-Ion cells to build a Li-Ion charger. The chip is completely pre programmed with the proper charging algorithm .. I'm not doing anything too special by putting it together with passive components to make it work.

One thing I do have quite a bit of experience with is electronics.. mostly I build LED drivers for fixed lighting. but have lately decided that I need a monster CREE torch.. so first I made some 3-4CREE buck drivers that work off 6 Li-Ion cells.. but then after looking around more I see I'd be quite out done. So I decided then that I needed more.. I now have 9 CREE R2s and I've built a ~35-50.4V buck driver that takes 12 Li-Ion cells in series and drives the 9 CREEs in series at ~96% efficiency. Adjustable from 1.2A to 60mA. I have a few extra of these drivers around too.. but I'm bench suppliless at the time.. I need to get another so I can finish all the testing to them and get efficiency numbers from all different input voltages and drive currents. Then I'll offer a few of those at cost to some CPFers too.

Building this charger is, electronically, a walk in the park. I should have the electric components by tomorrow. Follow my thread, I'll be updating as I go with pictures of everything. If you don't think you know what I'm doing by my work I post.. then by all means raise a flag.


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## SilverFox (Jun 8, 2008)

Hello Cy,

What do you think of his choice of charge controller chip?

Tom


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## Alan (Jun 9, 2008)

VanIsleDSM said:


> However I don't need any experience with Li-Ion cells to build a Li-Ion charger. The chip is completely pre programmed with the proper charging algorithm .. I'm not doing anything too special by putting it together with passive components to make it work.



No offense, this is exactly what most junior Chinese engineers are thinking and they manufactured hundreds of thousand of them. Yes, most of them charge OK and only a few fraction of them get into unexpected accidents when the cell reacts differently and beyond the limited knowledge of these engineers on li-ion cells. To them, it may be only a 0.1% failure rate but the consequence of this 0.1% could be serious if not fatal due to the nature of li-ion.

May be I'm paranoid but selling li-ion charger to public is very different from doing experimental projects that building 9A driver for mulitple LEDs.

I apologize if I am a bit too harsh or too paranoid.

Alan


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## SilverFox (Jun 9, 2008)

Hello Alan,

While I agree that people (including engineers) make mistakes, it has been my experience that almost all of the problems are generated from those who are trying to control production costs. It is not unusual for a production manager to make an "engineering" decision based on cost analysis, rather than heeding the original engineering findings and limitations. 

I respect that your work experience, culture, and day to day dealings with manufacturing may be different from mine.

By the way, what do you think of his choice of a charger controller chip?

Tom


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## jtr1962 (Jun 9, 2008)

SilverFox said:


> By the way, what do you think of his choice of a charger controller chip?


Since nobody else answered this thus far, to me it seems like a great chip _except_ for the fact that it is a _linear_ regulator. This means it requires a power supply fairly close to the voltage of the cells being charged to prevent overheating. For single cell charging 5V is good, 4.5V would be about ideal. If used with a 5V supply, a schottky diode to drop the supply voltage to the chip by 0.3 to 0.4 volts would be a good idea. It would also provide reverse polarity protection as a bonus.

A better but more expensive way to do this would be to have a switching pre-regulator to allow operation on more common 12V supplies. Also, the current requirements from the supply would be less. For example, a four bay charger requires 4.8 amps at ideally 4.5V. A 90% efficient switching preregulator could deliver this while drawing only 2 amps from a 12V supply (or ~1.75 amps from the 13.8-13.9 volts from a typical automotive cigarette lighter plug). Power bricks of over 4 amps at 12V are commonly available fairly cheap, making it possible to power an 8-bay charger. Also, by preregulating at 4.5V, heat buildup in the charger IC is kept to an absolute minimum.


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## VanIsleDSM (Jun 9, 2008)

If you haven't read through datasheets and put together your own drivers or controllers, and you're telling me I don't know what I'm doing... well.. you don't have any feet to stand on as far as I'm concerned.

There are chips exactly like this one in your ipod, your cell phone, your PDA your camera.. you name it.

The chip is pre-programmed.. the only things I have control over are, the charge current, 4.1 or 4.2V charge, charge timer, and what colour of LEDs I want to use.

Please.. look into the common schematic on the datasheet.. it's basically the same as I will be building it.. read through that datasheet, and then tell me a failure mode you see could pose a problem.

If all you have to say is "Li-Ion batteries are dangerous and you probably don't know what you're doing" Then please... take a seat.

/rant



SilverFox, Thank you for asking a worthwhile question.

jtr, Thank you for criticism that actually has thought involved. I agree a switching regulator would be best.. but the amount of components and complication that would add would be too much. And if I stick with linear I have no EMI to worry about. 5V supplies in the form of computer PSUs are very cheap and plentiful. Using a schottky diode would be a good idea if you needed to move to heat away from the chip.. but I don't. Each chip will have a heatsink thermal epoxied onto it, and each chip is equipped with a thermal throttling that reduces charge current to stop the chip from overheating.. you can actually connect these to 12V in a pinch and just use a lower charge current to keep the Pd down on the chip.. but it'll never melt down on you no matter what. Using a 5V supply the Pd isn't very bad..

0.8V x 1.2A = 0.96W... that will easily be dissipated by the heatsink.

Using a 4.5V supply would be great, but it would have to be deadly accurate to keep the charger working. 10% wouldn't be good enough. 4.5V is the bare minimum input voltage.

If you didn't want to use a computer PSU you could buy a 5V supply.. they're pretty cheap.

here's a 3 amp unit for $11, good for 2 bays.

http://www.powersupplydepot.com/prod...oduct=17430+PS

8 amp unit good for 4 bays at $15.

http://www.powersupplydepot.com/productview.asp?product=17432+PS

12 amp unit good for 8 bays at $17

http://www.powersupplydepot.com/productview.asp?product=17433+PS


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## cy (Jun 9, 2008)

no one is saying you don't know what you are doing... just that you might consider charging a few li-ion cells, then use it a few cycles to learn what common issues are. 

to answer silver's question about the chip... not familiar with this chip. but all the factors safely controlling a li-ion charge are there including low voltage cell conditioning. especially if temp sensor option is taken. 

one limitation is 1.2amp charge which would match 18650 charge for .5C. typical charge rate is 1C for li-ion cells, assuming one is using a quality hobby charger like Schultz or Triton. 

larger cells will not achieve .5C with 1.2amp limitations. 



VanIsleDSM said:


> If you haven't read through datasheets and put together your own drivers or controllers, and you're telling me I don't know what I'm doing... well.. you don't have any feet to stand on as far as I'm concerned.
> 
> There are chips exactly like this one in your ipod, your cell phone, your PDA your camera.. you name it.
> 
> ...


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## MrAl (Jun 9, 2008)

Hi there,

Just to note, we built a charger that works up to something like 3 amps
a short while back. It's a custom design with more than one ic chip,
so it's a little more involved, but it's good for the much bigger Li-ion
cells when you want to charge fast.
The project schematic and details appear right here on CPF although 
someone would have to do a search.


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## VanIsleDSM (Jun 9, 2008)

cy said:


> no one is saying you don't know what you are doing... just that you might consider charging a few li-ion cells, then use it a few cycles to learn what common issues are.
> 
> to answer silver's question about the chip... not familiar with this chip. but all the factors safely controlling a li-ion charge are there including low voltage cell conditioning. especially if temp sensor option is taken.
> 
> ...



Please explain how charging a few Li-Ion cells would help me build a charger? There's no other way I can put the thing together, it wouldn't change anything.

1.2A is not a limitation in the world of affordable chargers.. it's double the usual. 1C is only recommended for smaller cells, for larger cells like 18650 0.7C is the recommended max charging rate.

MrAl, 

I'd be interested in looking at that thread. Do you have any idea what I should search for to try and find it?

P.S. I'll charge some cells when I'm finished building the first charger


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## ProofTech (Jun 9, 2008)

MrAl said:


> ...The project schematic and details appear right here on CPF although someone would have to do a search.


Here it is.


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## VanIsleDSM (Jun 9, 2008)

Thanks ProofTech.

cy, as I already mentioned to SilverFox, the first charger will be dedicated to testing. michelkenny has been kind enough to send me some old cells he doesn't use anymore. After I'm done with it I plan to do a pass around for anyone who wants to scrutinize it..


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## cy (Jun 9, 2008)

if you had basic charging knowledge ... don't think you'd be taking that stance. 



VanIsleDSM said:


> Please explain how charging a few Li-Ion cells would help me build a charger? There's no other way I can put the thing together, it wouldn't change anything.
> 
> 1.2A is not a limitation in the world of affordable chargers.. it's double the usual. 1C is only recommended for smaller cells, for larger cells like 18650 0.7C is the recommended max charging rate.
> 
> P.S. I'll charge some cells when I'm finished building the first charger


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## VanIsleDSM (Jun 9, 2008)

cy, you're just making statements with no information in them.. why don't you explain what you're talking about?

I don't know if your electronics knowledge extends beyond batteries or not.. but if you had ever built something similar to this, I think you'd see there is no different way to build it to account for some charging observations. It is what it is.. it's already been designed, I'm just assembling it per some instructions.


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## jtr1962 (Jun 9, 2008)

VanIsleDSM said:


> jtr, Thank you for criticism that actually has thought involved. I agree a switching regulator would be best.. but the amount of components and complication that would add would be too much. And if I stick with linear I have no EMI to worry about. 5V supplies in the form of computer PSUs are very cheap and plentiful. Using a schottky diode would be a good idea if you needed to move to heat away from the chip.. but I don't. Each chip will have a heatsink thermal epoxied onto it, and each chip is equipped with a thermal throttling that reduces charge current to stop the chip from overheating.. you can actually connect these to 12V in a pinch and just use a lower charge current to keep the Pd down on the chip.. but it'll never melt down on you no matter what. Using a 5V supply the Pd isn't very bad..
> 
> 0.8V x 1.2A = 0.96W... that will easily be dissipated by the heatsink.
> 
> ...


I agree 100% with your reasons here since the goal is to make a high quality but low cost charger. In this case, a switching preregulator would add needless cost and complexity to the project. If I decide to order a few of these for myself, I may build a preregulator also just so I don't need to buy a 5V supply. Granted, I could run it off one of my home-made variable supplies, but I have loads of 12V supplies usually not powering anything.

Also, thanks for the explanation about the chip's thermal regulation. I only skimmed the datasheet. I didn't know it just reduces the charging current to keep the power dissipation within limits.


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## mudman cj (Jun 9, 2008)

I am following this thread with interest. I don't really need a Li-ion charger since I built the charger in the provided link (subsequently referred to as the linked charger), but I know what is involved in creating one. Again, I couldn't have built it without the patient help of MrAl. But, I am probably the only person that has built one like it. Why would I think that? Because of the cost in parts, time, and troubleshooting that was involved in building it and the lack of post activity to the thread. Don't get me wrong, I use the charger exclusively now for all cells from the 10440 to D and it's great, but it was not a simple charger to build (for me anyway). The chip that is the basis for the OP's charger offers a hitherto unseen level of functionality with a minimal parts count. 

I wanted to incorporate temperature sensing into the charger I built, but opted against the additional complexity in the hopes that it would be at a level of complexity that attracted some percentage of hobbyists. This chip has it built in. MrAl did a commendable job of simplifying the current sensing portion of the circuit to keep parts count down, but again this chip has internalized that portion of the circuit. It even has built in charge termination control, automatic slow charging for deeply discharged cells, reverse cell protection, status indication circuitry, and a limiting timer. I am rather envious of the capabilities this chip offers. Of course, like anything it has limitations. Awareness of these limitations is important in the design phase and in forming our expectations.

So what is my point? This project may end up being a simple and affordable charger that can be used to safely charge all of our Li-ion cells. Let's give the OP the benefit of the doubt and of our collective experience. I hope this works out to be the best charger it can be and I look forward to seeing the end product!


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## MrAl (Jun 9, 2008)

ProofTech said:


> Here it is.



Hi ProofTech,

Thanks for looking up that thread.

As for the chip being talked about in this thread, i'd like to see somebody look
into the possibilty of connecting two (or more) in parallel to get higher max
charge current. I havent had a chance to look into this myself yet.


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## FredM (Jun 9, 2008)

I don't understand why all the hate comes out. Seems like a pretty good service to CPF.


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## cy (Jun 10, 2008)

again.. if you had basic charging experience and understand basic issues that arises from using li-ion cells. you'd understand what I'm referring to. 

Please don't get me wrong... I think it's great that you are building something for cpf'ers. 

Mr Al and Silver is on board... it's hard to find better help then these two!!

I really do wish you and this project well.... no need to reply... I'm bowing out of this thread. unless something really changes...



VanIsleDSM said:


> cy, you're just making statements with no information in them.. why don't you explain what you're talking about?
> 
> I don't know if your electronics knowledge extends beyond batteries or not.. but if you had ever built something similar to this, I think you'd see there is no different way to build it to account for some charging observations. It is what it is.. it's already been designed, I'm just assembling it per some instructions.


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## VanIsleDSM (Jun 10, 2008)

Thanks mudman, good post.

MrAl that's an interesting question, I'm not sure how the double voltage sensing would work out though.

FredM, I'm not entirely sure. There is often pessimism from those who only read about doing things like this.. and never actually get to build anything.



cy, again, you just speak of these so-far mythical issues without any real information or explanation.

If you had basic knowledge of adding passive components to IC chips then you wouldn't be saying what you are 



cy said:


> I'm bowing out of this thread. unless something really changes...




Thank you, I appreciate that. Feel free to post again if you actually have some information instead of your repetitive unfounded discouraging comments.


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## VanIsleDSM (Jun 10, 2008)

So I got the electronics this morning as I thought I would.

Made some finishing touches to the PCB design.. and here we are:







Some Crees for reference. The heatsink will be thermally epoxied onto the chip when I'm done.

There are 5 slots to stick the wire in for adjusting the charge current. From left to right it's:

250mA 500mA 750mA 1000mA 1200mA

and leaving the wire disconnected is 100mA.

Now I just have to wait for some batteries in the mail to try this guy out! 

One thing I was able to test was the temp shutdown.. I touched a half cool soldering iron to the negative terminal contact, where the temp is taken.. and the red LED started flashing.. then shortly after removing the iron the LED went out.

I'm eager to try it with a battery, it's all up to you now michelkenny! can't wait to get those cells..


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## michelkenny (Jun 10, 2008)

VanIsleDSM said:


> I'm eager to try it with a battery, it's all up to you now michelkenny! can't wait to get those cells..



I'll try to mail them out today! Can't wait to replace my crappy $10 Trustfire charger with this.


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## linterno (Jun 10, 2008)

VanIsleDSM said:


> So I got the electronics this morning as I thought I would.
> 
> Made some finishing touches to the PCB design.. and here we are:


Just a comment:

There is some risk of short circuit with the red and green LEDs. You should isolate them better. If you push them down the LED's negative leg could touch the positive trace and create a short circuit.


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## VanIsleDSM (Jun 10, 2008)

I bent the lead so it won't touch.. you could make it touch if you wanted to.. but it won't short during normal use. 3mm LEDs are the least of your worries when you're hand soldering SOIC.


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## Citivolus (Jun 10, 2008)

linterno said:


> Just a comment:
> 
> There is some risk of short circuit with the red and green LEDs. You should isolate them better. If you push them down the LED's negative leg could touch the positive trace and create a short circuit.




Whilst that trace makes me nervous too, looking at the data sheet there is no danger of shorting, as those pins are self current limited to between 8 and 12 mA. The LED would just stop working.

Out of curiosity, are you planning a solder mask for the production run?

Regards,
Eric


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## VanIsleDSM (Jun 10, 2008)

Nope.

I don't have the ability to create a solder mask. I'm not really doing a production run, 25 isn't quite production status.

If this all works out well and I make more in the future.. then I'll have the boards made with a solder mask and I'll SMT them in an oven.. I have many hours of soldering ahead of me doing it by myself.. but I'm ok with that for just 25.

If you were holding the PCB in your hand.. you won't be worried about it, believe me.. I can see it from angles you can't.. it's perfectly fine. I even tried pushing it down on the trace but it's not going anywhere... you'd have to break the solder joint to short it.


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## Flashlight Aficionado (Jun 10, 2008)

VanIsleDSM said:


> cy, again, you just speak of these so-far mythical issues without any real information or explanation.
> 
> If you had basic knowledge of adding passive components to IC chips then you wouldn't be saying what you are
> 
> Thank you, I appreciate that. Feel free to post again if you actually have some information instead of your repetitive unfounded discouraging comments.



Trying not to be a catalyst for an argument, but if you just looked at cy's signature, you would have gotten a clue.

Here is cy's signature link I mentioned - 
greatest danger using li-ion cells occurs during re-charging


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## VanIsleDSM (Jun 10, 2008)

I'm pretty fed up with all of this.

Here I am putting in tons of my own time and effort to get better, safer, chargers out to some CPFers for the cost of the parts only..and all I'm dealing with flack and bullcrap.

I'm tired of it.

I could easily just drop all this and sell them on ebay for a lot more.

I've read cy's recharging post.. it's all very elementary. 


Anyone who could not easily build their own Li-Ion charger from past electronic experience should now stop typing if you only have something negative to say. Your posts are a waste of bandwidth.

I probably won't post here again until I'm finished everything.. tired of being bashed on for performing a service that 99% of you naysayers have no qualifications to critic.

:shakehead


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## MrAl (Jun 11, 2008)

Hi again,


Sorry i didnt have a chance to look at the chip being talked about here until
now. I have a few suggestions.

The QFN package has a thermal resistance of 37 deg C/W, and the
SOIC package has a thermal resistance of 74 deg C/W.
At 25 deg C and worst case 2.5v cell voltage and 5v input voltage
and 1.2 amps output current, the little package will have to dissipate
3 watts. This will heat the thing up, and thermal regulation will set in.
The QFN package will cut back current to 1 amp (not too bad) but
the SOIC package will cut back the current to about 0.5 amps.
This makes the QFN package preferable, if it is possible to solder that package
properly.
With elevated ambient the situation will get worse, but as the cell voltage
comes up to 3v the output current will rise and start to put out full current
with the QFN package, but with the SOIC package about 750ma limit.
At 3.5 volts the situation will be better of course.

This means the little chip will get pretty hot, but it should work at least
to some degree. If the thermal current limiting is to be avoided then a chip
that uses an external pass transistor could be considered instead. That
would allow for the mounting of a heat sink if needed.

This is all theoretical however, using the data on the data sheet and general
physical principles. Since this is a small package and the power dissipation
can be quite high (fairly high for a small package like this) i think a prototype
is a given. I have to suggest then that one unit be built and tested at the
extremes to see if this chip will perform the way we want it to. It may even
be a good idea to work with two different chip candidates and choose the
final device after the tests are complete.

Also, to satisfy the safety conscious, each unit built should be properly tested
at the extremes of operation to make sure they all work ok. This should
guarantee that each unit is safe to use.


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## VanIsleDSM (Jun 11, 2008)

I've been coerced to post again by your response MrAl. I truly enjoy the intelligent comments.. too bad there's so much trash to sort through in this thread now.

The reason the QFN package has less thermal resistance is because it has a solder pad on the bottom to draw out the heat. This works much better than the SOIC if you plan to use a copper patch on the board for your heatsink, and thus the lower resistance. This is irrelevant for my design though, as I'm going one step further. I'll be mounting the heatsink pictured right onto the chip with thermal epoxy, far better than the copper patch method.. though I have left copper under the chip for more dissipation as well.

The heatsink I've chosen will dissipate 2W @ 50C by convection and radiation. Obviously more at higher temps. I haven't tested yet, but I expect this heatsink to keep the chip out of thermal regulation in all situations.

I do plan to fully test each charger.. as I do with all the electronics I design and build.


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## MrAl (Jun 11, 2008)

Hi again Van,

If someone comments something that you dont like, dont let it stop you from
posting here as that's exactly what some people are after. Some sites are
even worse as some people post just to start trouble. That messes up the
whole site but i guess that's life. Other people are just concerned and maybe
they just want to express their concerns and it's as simple as that. Once this
thing is tested and working it should be a decent design i think, so dont 
give up hope on the site ok?

Anyway, do you know the thermal resistance from the die to the heatsink?
The reason i ask is because it may be higher than we'd like it to be. I dont
have any numbers in front of me so i cant calculate the temperature rise.
I guess you could try doing a profile next, since i see you already have one
circuit built up. Connect a cell that is depleted to 2.6 volts say and log the
current and voltage, or even just the current, and we'll take a look and see
how this thing is behaving at room temperature and over the whole charge
time. This will tell us if this is a workable design or not.
I'd like very much to see the results of this profile test, if you can get to do it.


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## VanIsleDSM (Jun 11, 2008)

Thanks MrAl.

I agree the thermal resistance may not be ideal.. But I still think that heatsink will keep the the chip in check.

I don't have any cells to test right now, but I should by early next week. I'll most definitely do all I can to try and make this chip hit thermal regulation to see how much headroom I have. The voltage rises very quickly after the precondition.. so I don't think the heatsink will even have to dissipate ~3W of heat, as it won't have reached it saturation point.. I think the Pd will probably be down in the 2W range before the sink saturates at around 50C and slowly starts cooling as Pd lowers even more.

That's my guestimation play by play.. can't wait to see what happens for real..


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## VanIsleDSM (Jun 13, 2008)

It's alive!

All goes well so far.

I've charged a couple 16340s without the heatsink @ 750mA to see how it worked.. then I put on the heatsink.. and drained an 18650 through some nichrome wire until cutoff and then put it in the charger to see how the thermals were handled.

I didn't think thermal throttling would kick in even with the high resistance of the SOIC because it would have some PCB relief on the back and the heatsink on the top. But I was wrong! not a big deal though.. it cut back to 1.05A and the heatsink stuck right around 45C. Shows just how bad the thermal conduction of that SOIC is.. too bad I can't hand solder a QFN.. though I don't think it would help much as I'm still trying to pull the heat out the top.. ideally you'd have a QFN on a MCPCB.. but we're going for affordability here. At any rate I'm not too worried about ~200mA cut back.. However I am going to try jtr's suggestion of a schottky diode on the input to cut back the voltage to just above 4.5.. I have some on hand to try out.. but I'd need to order more for the chargers.. these look like a good candidate, http://www.vishay.com/docs/88740/sl12.pdf

0.34V drop will give some headroom still to work with crappy supplies not putting out quite 5V.. but still cut down on some heat dissipated by the chip.

Charge voltage was bang on, exactly 4.20V in CV mode on a 16340, the cell itself once removed was 4.18V, and then dropped quickly to 4.15V.. and now it's 4.13V.. A trustfire grey. I imagine that's normal for the cell to slightly drop?

The 18650 is still charging now.. I'll wait until it's done and then put the schottky inline and check the thermal throttling again.


Edit:

Seems the charge cut-off is quite conservative. The 18650 finished in a little over 2.5 hours.. was being charged at 4.20V and came out reading 4.17. Because the cut-off is 8% of the charge current, I switched it from 1200mA to 750mA and the charge went another half hour or so, and came out at 4.19V. If you want to fill it right up, remove the wire completely for 100mA charge... but I don't think that's recommended. This cell isn't dropping at all.. so I'm thinking maybe that 16340 isn't in the best of health or something.


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## MrAl (Jun 13, 2008)

Hi again Van,

Initial testing doesnt sound too bad i guess. I calculated the SOIC package would
drop to 0.75 amps when it went into thermal regulation, so if it's at 1 amp that's
even better. The problem with getting the heat out of IC's that are not made to
be heat sinked is that the thermal resistance junction to case is just too large,
which creates a large thermal drop, which keeps the die hot even though the outside
is cool. It sounds like the heatsinking is working at least a little however, so that's
good to hear.

Dont be afraid to use a resistor on the input either to drop a little voltage if
you feel like trying that. The nice thing about using a resistor is that once the
max current drops off the voltage will rise near 5v again which will make sure
the cell gets charged right up to 4.200 if that's what you want.
If you want to drop 0.400 volts then you need 0.33 ohms, maybe make it
a 1 watter. As the current drops the voltage drop will decrease too which
should work out very nicely. You can make a few measurements to confirm.

I have to say that i am impressed by how fast you got all this together.


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## dom (Jun 13, 2008)

Top stuff _VanIsleDSM _
All this sounds very interesting and going well by the looks of things -but i knew that it would after seeing the driver you made for you light project 

Cheers
Dom


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## geek4christ (Jun 13, 2008)

Watching this thread with great curiosity. I think it's great that you're doing this, VanIsleDSM. I'm hoping this little project is a success.


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## VanIsleDSM (Jun 13, 2008)

Thanks everyone, I appreciate the kind words.



New report.

The schottky didn't fair so well.. the output current drops considerably more.. to about 700mA. I don't think the chip likes a 4.5V input with max output.

I then tried 0.3ohm, current didn't drop as much, but still dropped to about 900mA.. then I went to 0.24ohm and got ~1A.. but nothing charged as high as a straight 5V connection... 1.05A. I've been shopping for another CCCV power supply since the one I had on a long term loan was recently taken back.. If I had one I would try increasing the voltage slightly to see if I could get a higher current.

I do suspect though.. that this chip just charges at that rate as it's maximum.. You'd think with a cool heatsink the thermal reg wouldn't kick in until it was had heated up somewhat.. also.. as the battery charged and the voltage went higher, so Pd goes down, the charge current never came up to a full 1.2A. In fact it never went higher at all. I took another look at the data sheet.. and this is within spec for a max charge current... it can range from 1020mA - 1380mA.. so.. maybe.. I'm hoping.. that this charger isn't even in thermal regulation, but this is just it's rate of charge. I will put together another couple PCBs here soon and test them out to answer this question.

I've been discharging and charging all day.. everything so far is A-OK :twothumbs


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## MrAl (Jun 13, 2008)

Hi again,

Ok, the chip isnt performing as well as the data sheet suggests as typical
(what a surprise there ha ha), but it still seems to be working out somewhat.

To find out what the max current capability of the chip is, all you have to do
is keep the cell voltage above that which causes the die to heat up to where
thermal regulation would kick in. For example, thermal reg is most likely taking
effect when the cell voltage is 2.5v and current is (trying to be) 1.2 amps,
but when the cell voltage is say 3.5 or maybe 3.8 volts, the thermal reg
should not be limiting current at all. This means all you have to do is measure
the current at maybe 3.5 volts and see what it is (assuming the chip started out
cool).
Cooling of a die inside a chip usually comes from a low thermal resistance path
that the manufacturer builds into the device so that the difference between the
die and the outside case surface stay as close together as possible. With a 
regular chip that does not have this feature (the SOIC package we are dealing with
now) the heat has to travel through a relatively high resistance heat conductor
(the plastic package) before it reaches the surface. This means even a very good
heat sink wont help as much as we would like it to. The difference here is in the
spec's given by the manufacturer:
SOIC is around 70 deg C per watt,
QFN is around half of that, 35 deg C per watt.
If the QFN package is half that of the SOIC then we can see that the plastic
of the SOIC package is what is stopping us from being able to cool the chip
down the way we would want to. If the heatsink is cool yet the chip is in
thermal regulation then that just confirms the large heat resistance. Heck,
we could have as much as 70 deg C difference between the die and the 
heat sink, which means the heat sink is at 25 deg C while the die itself is at
95 deg C. A little higher and it goes into thermal regulation.

Hopefully the chip can perform better than the data sheet, which might
mean we can get higher current out of it. The QFN package would be 
better however, but yeah that's going to be harder to solder.

Another interesting test would be to test with a 2.5v load and 5v input
and check the current with and without the heatsink.

If the chip could perform better with more than 5v input that would be
interesting, although the critical question is how much output current
there is with 2.5v cell voltage as the die heats up.


----------



## VanIsleDSM (Jun 15, 2008)

Once the cell voltage was up to 4.1V it still wasn't at 1200mA.. was still around 1050mA.. but like I say.. that's within spec for a max charging current.

My well used touchometer said 45C, but I was a little off.. it was 48C when I actually measured the heatsink.. which means it's dissipating almost a full 2 watts of power.. it's most definitely helping, I think without it the chip may even hit total thermal shutdown having to try and get rid of those other 2 watts all by itself. 

The thing is.. even with a cell that's been taken to cut-off of 2.75V.. the charger right at the start is never putting out less than 3.6V or so.. it doesn't exactly match cell voltage.. it's higher.. so it's not burning as much power off as initially expected.

For the QFN.. I agree it would be better.. but you could only make use of that better thermal resistance by use of a MCPCB.. which is pretty costly.. or better yet, thermal vias in some FR4.. but I can't manufacture that myself... nor can I solder QFN by hand.. I don't think so anyway.. never tried.

However.. if all of this goes well and I do another run of these chargers.. I'll have the boards made with a solder mask and thermal vias. I'll then invest in a soldering oven controller and properly SMT the QFN package to thermal vias and heatsink the top.. that will absolutely ensure cool operation. I'm also going to get in touch with Microchip Technology and see if it's possible to parallel these chips.. it would be easy to configure a 4 bay charger to be able to switch into 2 bays @ 2400mA or 1 bay @ 4800mA for some uber sized D cell or some parallel packs.

Been a busy end of week so far.. I haven't soldered up the other PCBs yet to test their charging current but they've got the design laid out and ready to etch.. I'll probably get it done tomorrow.


----------



## MrAl (Jun 15, 2008)

VanIsleDSM said:


> Once the cell voltage was up to 4.1V it still wasn't at 1200mA.. was still around 1050mA.. but like I say.. that's within spec for a max charging current.
> 
> My well used touchometer said 45C, but I was a little off.. it was 48C when I actually measured the heatsink.. which means it's dissipating almost a full 2 watts of power.. it's most definitely helping, I think without it the chip may even hit total thermal shutdown having to try and get rid of those other 2 watts all by itself.
> 
> ...





Hi again,


It sounds like the chip can only put out around 1 amp then, which means it's not
running as high as they claim...it's at the low end, so either we got unlucky or
they overrated the chip.

That's interesting about the 2.5v rising to 3.6v right off. Is this a new cell being tested,
and what kind is it? This could vary with cell capacity.

Because these are linear current regulators when in the current mode, i would guess
that they can be paralleled with some degree of success. The problem with paralleling
regulators is that the voltage of each one fights for control, but these chips seem to
be very well matched (hopefully they are up to spec). This means that both regulators
will contribute to the total current (1 amp lets say) until the voltage gets up to around
4.00 volts or so, at which if one regulator is at minimum spec and the other is at max
spec one regulator will put out the full 1 amp while the other will put out maybe 
600ma or so, which isnt too bad either i guess...not as high as we would like, but
perhaps still acceptable.
The pass transistors are MOS, so probably current sharing resistors wont be needed,
unless the low spec chip in the pair draws current. If so, 0.05 ohm matching resistors
can be used on the output of both chips which will help with the matching for the
unlucky combo of a pair where one is at min and the other is at max. Of course
testing is mandatory, as well as careful measurement of the output voltages of
both devices if possible but at last input current to both devices of the pair.

In any case, it sounds like everything is going pretty well so far


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## VanIsleDSM (Jun 19, 2008)

Just a quick update.. I've soldered up another 6 boards now and each one was 1.05-1.08A. This was without a heatsink.. before any thermal regulation.. the charge current then starts dropping quickly due to the heat... in less than 30 seconds it was down to 0.6A (the one that I tested for that long) 

So the heatsink is indeed doing a lot.. it keeps the chip right around it's max charging current.. maybe dropping 50-75mA due to heat.. but barely anything.

It appears these charging chips are somewhat of a lottery just like LEDs can be.. you get anything from 1020mA -1380mA.. and since the chips I have in the tube are probably all from the same batch.. they're almost identical.

jtr, when you have yours set up.. be sure to post up what your max charge current is.


----------



## VanIsleDSM (Jun 20, 2008)

Just soldered together and tested another 8 circuits.. quite a bit of work.

I thought I would take some pics of the whole process since this is a safety sensitive issue.

Since someone could reverse engineer my PCB design and such along with all the other components and build your own.. I think it's necessary to state that I won't be held responsible for any personal or property damage from the cell being recharged or the charger itself.

First off the boards with solder paste carefully blobbed onto each contact for the passive components.







Here are the components placed onto the board, doing this with tweezers.. along with the application of the solder paste is the most lengthy, tedious part.






Now we have the passive components soldered on. I do them first.. as the chip is ESD sensitive... and it will also receive less residual heat from soldering other components this way. It's almost impossibly to not move the components slightly when you place the toothpick on it to hold it down for soldering. I will be buying an SMT controller soon and making a surface mount oven.






Here the LEDs have been soldered on and I've positioned the chips, soldered one area to hold them in place, and then applied the solder paste.






Finally I add the current selecting wire and the sockets for it (stuff that would be annoying to work around if it were added earlier) I'll be adding some shrink tube to the selector wires to isolate them later. Solder paste is great.. I've done SOIC before by using regular solder and tinning everything.. not only do you have to double heat the chip that way.. but you never get it to lay flat.. and it's very time consuming. With the paste it's much easier.. and when you solder it you can be on and off the legs so quickly with the iron.. not even a second and it's done.. just a little jab with the tip.






And here's the super close up with the toothpick for reference.






I ran out of copper clad board.. I never seem to have enough! so I need to get a bit more and build the charging bays themselves. Stay tuned.

The savvy among you might pick out something that looks unconnected in the last pic.. no need to worry.. it's just ground equalizing.. as there are 3 ground pins the others connect under the chip.. however I will bridge it over before I have it all done. Just had to do with the sizes of the boards and how many I could fit... the last one had to be like that.. so I could utilize all my PCB material with the least waste.

Why is it that I can only post 800pixel images? I don't think anyone runs a resolution that low anymore.. Just curious.. as I'd really like to put up some higher quality pics... they look so small on my screen.

P.S. These 8 chargers were all again between 1.05A and 1.08A.


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## tpchan (Jun 20, 2008)

Thanks for the pics and your great work on this project. Frack all the naysayers.  I can hardly wait for my two bays to be delivered. Please PM with payment details as you get closer to completion.

I think all you can do is post small pictures and then make links that take you to the larger images if people wish to click on through. I am reading this thread all the time and not posting that often, but I just thought you should know there are people here that are extremely grateful for your hard work!


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## dom (Jun 20, 2008)

Wow -didn't think there was that much work involved -looks fantastic.

Perhaps larger pix take up more bandwidth or something? Can you link them to your host site for people interested in more detail?

Cheers
Dom


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## mudman cj (Jun 20, 2008)

Is anyone else not seeing these pics? Edit: never mind, I can see them now. :shrug:


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## CT90 (Jun 20, 2008)

This is very impressive work and a great thread. Thanks for sharing your work. Learning lots here.


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## michelkenny (Jun 20, 2008)

Looking good! Can't wait!


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## VanIsleDSM (Jun 20, 2008)

Thanks everyone. I appreciate the kind words.

I zoomed in on the pics for more detail and here they are again.. almost as good as being able to post a full picture. 800 is so small.. 1024 is a much more realistic limit for these days...anyway.. here they are.


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## Mr Happy (Jun 20, 2008)

VanIsleDSM said:


> I zoomed in on the pics for more detail and here they are again


So, do you want critical feedback on your soldering?     

(Never good to zoom in too close )

(Just pulling your leg )


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## VanIsleDSM (Jun 20, 2008)

Mr Happy said:


> So, do you want critical feedback on your soldering?
> 
> (Never good to zoom in too close )
> 
> (Just pulling your leg )



Haha.. anyone can criticize it.. but not without a sample of their own!


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## [email protected] (Jun 21, 2008)

Just a relatively simple question... are you using lead based solder (or that newer RoHS substitute) for this Smart Li-Ion charger prototype?


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## MrAl (Jun 21, 2008)

Hi again,

Looks like this project is working out nicely. Since the heat sinks seem to be helping,
i'd keep using them.
Nice pics too, which makes for more interesting reading if you ask me...always nicer.


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## zapper (Jun 22, 2008)

Outstanding work VanIsleDSM ! :twothumbs

I'm glad you haven't paid attention to the detractors and are having fun with this.

After all, if it's not fun or rewarding then what are we here for ? :shrug: :grouphug:

Looking forward to the completed project. I'm ready on my end. 

(due to the parts quality received maybe we should change the title to "1200mA_ish_ _Med_HIGH QUALITY Li-Ion charger discussion thread.":lolsign:


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## VanIsleDSM (Jun 22, 2008)

zapper said:


> (due to the parts quality received maybe we should change the title to "1200mA_ish_ _Med_HIGH QUALITY Li-Ion charger discussion thread.":lolsign:



Haha.. Thanks zapper.. and good point!

I never meant quality like the expensive hobby chargers.. it's a statement in comparison to the likes of the DX chargers. It is within spec, so we can't really call them out on it... I have a sneaking suspicion that the QFN packages may boast the higher charge currents.. jtr said he ordered some of these.. I'm interested to see what he gets for a max charge current.

Hopefully I can have all of these done by the end of the week. I cleaned out Canadian Tire of all the springs I'm using.. and I need more, but I haven't hit up the other 3 or 4 in town, so I'm sure I can scrounge up enough. I may just try going to Acklands and seeing if I can get some the same size in bulk.


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## MrAl (Jun 22, 2008)

Hi again,

I think this *is* a high quality charger because it can do all of
the things that make a high quality charger just that...conditioning,
accurate regulation, and the current is high enough (1 amp) to
make it fast enough too, and auto turn off. It's relatively small
too which is also nice.

If the name is to be changed i would select this:

"High quality 1 amp Li-ion charger"

and that's it.

There is one thing that would make it better, even much better, (it's
still high quality without this though), and that is a pre switching
regulator. The pre switching regulator would take a wall wart that
is rated 9 to 24 volts dc and convert it into 5v dc for use by the
circuit as it is now. Some wall wart ratings would be such as these:

9v, 500ma
12v, 400ma
15v, 300ma
20v, 225ma
24v, 190ma
28v, 160ma
32v, 150ma

This would greatly relax the +5v regulated input requirement, meaning
the end user would use this circuit with almost any ol' wall wart they
have laying around. My current charger uses this technology and
i have to tell you it is really nice to pick up any old wall wart and
start charging. This also means that single wall wart can be shared
with other chargers or other devices (i charge my 12v battery with
one of the wall warts i charge my Li-ion cells with too).


----------



## jtr1962 (Jun 22, 2008)

VanIsleDSM said:


> I have a sneaking suspicion that the QFN packages may boast the higher charge currents.. jtr said he ordered some of these.. I'm interested to see what he gets for a max charge current.


Were you measuring the current by putting a multimeter between the charger and the battery? If so, the multimeter leads generally have a resistance of a few tenths of an ohm. This might account for the slightly less than nominal measured current. A better way might be to put a very low value resistor (say 2 or 3 0.1 ohm resistors in parallel) in between the charger and cell, measure the voltage drop across it, and use ohm's law to figure the current.

I haven't ordered any of these to play with yet. I was going to last week, and then the sewer backed up into the basement. Now I have a mess to clean plus I'm paying $1500 towards repair of a corroded pipe. It might be a while before things get back to normal in my lab. I'll certainly keep you posted whenever I do get around to testing the charger IC. Yes, Mouser has the QFN so that's what I'll be getting.

Nice soldering work BTW! One trick I use to get SMD ICs to lay flat without soldering paste is to tin just one pad on the pcb. I then lay the IC over this pad, melt the solder while gently pressing it down, and make sure the rest of the pads are lined up. Once the IC is stuck down with one pad, I can solder the rest. I do something similar for SMD components with fewer pads. Basically the idea is to lock it in place by soldering one pad, and then solder the remaining pads. For mass production I'll generally use double-sided tape to stick the PCBs to a floor tile so I can get at the boards from all four directions without spending time moving each one individually. Also, the boards are preventing from moving while I'm soldering. No need to do this with the volumes you're producing, but these techniques come in handy when you're soldering 500 boards at a time (yes, I've done that ).


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## zapper (Jun 26, 2008)

Anymore progress made in testing or finding the springs required VanIsleDSM?

BUMP


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## VanIsleDSM (Jun 27, 2008)

I think I like "1A+" for the name. hah.

A pre-switching regulator would be nice indeed, and I've looked into this option. A 5A switching reg than can take 9V-24V would cost me around $30-40 to make  So it's just not worth it.. if I were to utilize a switching design it would make more sense to just use switching charger chips and root out all in the inefficiencies rather than supplying a linear charger with a switching supply. I've only constructed a few DC-DC buck drivers so if anyone knows of an IC that'll allow me to make something that'll work for around $10 a piece then I think it'd be worth it... but I can't find anything myself that would be affordable and do the job. If it costs any more than that.. then it makes more sense to just buy one of the 115VAC-5VDC power supplies that I posted earlier... or an old $10 computer power supply.

Sorry to hear about your plumbing problems jtr.. that doesn't sound like fun. Thanks for the soldering compliment.. I also often use double sided tape to hold things still.

As for my progress.. I admit there hasn't been a lot this week, a good friend of mine returned after a year working abroad.. this week has been filled with beer, golf, BBQing and debauchery. I did however manage to get all the machine work done on all of the PVC end caps. I had no luck with the springs from acklands, but I was informed of another place that might be able to get them for me, I'll check on monday, and if not then I'll drive around to all the Canadian Tire stores and buy up all of their springs.. Won't be much longer now, I promise.


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## MrAl (Jun 28, 2008)

Hi again Van,

Just wondering, why do you want a 5 amp switcher, to run 5 units at once?
I was talking about a smaller regulator for each linear unit really, but yeah 
the more current the better.

Let me ask you this: How much would it cost you to make the PC board alone
that could hold one 6 pin IC chip (a power IC), a 1 inch diameter toroid, and
a few other components (two or so resistors, two or three caps) about 
2 inch by 3 inches overall ??
Perhaps i could make the pre regulators if i could get someone to get the 
PC boards. I've made several switchers in the past as well as hundred watt units
and even higher (30,000 watts) but i dont have my PC board making process
completed yet.
Another idea woulld be (4x3 inch board or so) to have it interface with the PC
computer, so the user could monitor the charge progress. Again, i would only
need the pc boards. Sound interesting? I'd also be wondering who else
is interested in a finished product.


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## VanIsleDSM (Jun 28, 2008)

For a pre-regulator it would make sense to have 1 unit to be able to supply power to up to 4 chargers. If you're going to build a pre-regulator for each charger bay, it would be worth it to use a different charging chip, one that utilizes a switching design itself.. then there would be no need for a heatsink or any thermal considerations. Of course the cost and complexity goes up, but still less so than having a switching pre-reg with a linear charger for each bay.

I'll look into making some switcher chargers after I'm done with these. As for making PCB boards, I'll do it in exchange for your teachings on the computer interface, sounds very interesting. Is it a USB or a serial infterface? And how do you monitor supply current? Hall effect?


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## zapper (Jun 28, 2008)

Hey Van, you can't argue with a good time with friends, more fun to you! 
:twothumbs:buddies::drunk:


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## MrAl (Jun 30, 2008)

Hi again Van,

Well, i make chips that interface with the computer RS232, but
with the lower cost RS232 to USB interface 'cables' available
these days it can be easily switched to USB instead.
The chips have four analog ports that can be used to sense
either voltage or current, but when sensing current you
either need a resistor (some loss of efficiency) or an 
amplifier with a small series resistor (low loss of efficiency).
There are several ways to approach this kind of measurment.
The RS232 chips mainly need a voltage regulator (small +5v regulator)
and a few resistors to work, or an opto isolator to completely
isolate the computer from the measurements.
I was thinking of a board with a switching regulator on it
plus one of these chips, and of course associated Windows
software to read the votlages and currents as the cells are
charging. If you want to build up switching IC chargers though
that's cool too. I assumed that since you were building these
that you didnt really want to do that, since that would surely
be the best choice to start out with anyway.
BTW i sell the chips for about $5 each but maybe for 10 units
i could go down to $4.00 i guess, as long as i could get my
raw materials for the same as i have paid in the past. The software
has built in alarms to sound off if something goes out of spec,
like maybe max current or overvoltage.


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## Flintstone (Jun 30, 2008)

I remember seeing this thread start and thinking this was some newbie who was just blowing some steam thinking they could change the world (hehe sorry - atleast I didn't post anything then!). I'm now more thinking something like this could be a great contender and respect the work that has been done already. Apart from those Pila chargers there frankly isn't any charger out there that satisfies our concerns about safety and quality, and something like this could well be developed to a mature product and end up being highly recommended ie. like the AW cells :twothumbs.

So please stop criticizing the product until it's ready!


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## VanIsleDSM (Jun 30, 2008)

MrAl. I agree that switching chargers would be the best option, but my intention when building these was simplicity and affordability. The original reason in making these chargers is that I'm building a 9xCREE torch with 12x18650 cells powering it, and I wanted a way to charge all 12 at the same time without too much money thrown down for a 12 bay charger.

Since there was a lot of interest I decided I would relinquish another 6 of the ones I wanted to keep to lucky CPFers.. I'll build another 6 for myself at a later time... I think I can handle 2 charging runs... the torch should have a run time of about 4 hours on full power, so I won't have to be charger all the time or anything.

Which chips are you speaking of? I have some experience with picaxe micro controllers.. sounds very similar to what you're using, with an RS232 interface. I still think the best way to measure current would be a hall effect sensor if it could be done economically. The only thing here that I haven't already done before would be to write the software on the computer and maybe make a little GUI to show the charging state.

Flintstone, Thanks for the kind words, I appreciate that.


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## MrAl (Jul 1, 2008)

Hi again Van,


The chips i am speaking of are chips that i make myself and sell
for a very cheap price. It's more of a hobbie for me these days
however so i dont mind if i dont make any money really, just
as long as the parts i buy are paid for.
The chips are complete in that they provide the user with
four channels (but more in the future) of analog inputs for
the computer, of which allows them to read voltages external
to the computer (such as battery voltages). To read currents
some kind of conversion is required, such as with a resistor.
Yes, Hall Effect devices can be used but they end up much
more expensive, and there are also current to voltage converter
IC's out there that sell for less than a dollar that work pretty
well too (SM packages mostly).


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## VanIsleDSM (Jul 2, 2008)

Interesting MrAl, but I don't quite understand, I imagine you're not actually manufacturing these chips, so I'm not quite sure what you mean by "making them myself"

I have a somewhat unfortunate update to the charger situation. I've gone all over town looking for some more of these springs, one other store only had 1 in stock, and another didn't have any. I've looked around on the internet on sites like enco as well.. and they carry springs, but nothing in the exact same size. So.. I went back to Canadian Tire and asked if I could order a bunch of them, which I can, but it's going to take 2-3 weeks before they get here. I see no other option at this time though.

I'm pretty much done building everything, I just have to assemble the chargers and drop the spring in, so I'll get everything as far along as I can, when I do get the springs it'll be no more than a day before they're all ready.


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## MrAl (Jul 2, 2008)

Hello again Van,

Well, it's a bit of a trade secret how i make these chips, but
nevertheless when someone orders one they pay me 5 dollars
and i send them a chip via snail mail and the custom software 
via email and they build their own pc board.
The chip reads 4 analog ports and sends the info to the computer
and the included software is made to monitor charging of cells
in many different ways. I also include lots of schematics to
show how to do different cells and what to enter into the
software. The chip/software can also measure temperature
via cheap thermistors in case someone wants to measure their
cell temperature while charging. The alarms in the software 
get set to go off if something goes out of spec. Of course
there is logging of the entire charge process as well as 
computation of the actual capacity of the cell assuming a
previous full discharge.

I am in the process of trying to find a cheap pc board source
so i can make complete boards and maybe even complete
units with test leads and everything.

Anyway, i thought it would be cool to have one of these chips
built into the charger board too. Monitoring would then be
possible by plugging the charger into the computer via RS232.
Since you were building boards anyway i thought it might
work to do this but you seem to be trying to keep the price
at rock bottom so i dont know. I cant sell the chip for less
than 4 dollars in quantity i dont think, at least not yet.
BTW as far as i know this chip is not available anywhere else
(at least not this exact chip) because it is custom designed.
Interestingly, it runs on 5 volts too and has to be the easiest
chip to use because there are so few extra parts.


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## VanIsleDSM (Jul 2, 2008)

I see.

Thanks for elaborating a bit. These specific chargers I'm building and sending out I want to keep as they are. There's a list of people in the MP who are getting one, and I'm not going to change what they think they are getting or the price on them now.

But that doesn't mean I wouldn't like to experiment with this and my own tinkerings. I wouldn't mind building a slightly higher end switching charger. I've been scoping out a few other chips for this lately. It would be best to incorporate the switching charger and the interface on the same board so you could easily tie in the thermistor for temp monitoring and such.

I can make a few boards for a better price than you would get from some company, but I wouldn't say I'm equipped for huge quantity. Do you have a design? how large? I mean.. if I can fit 100 of them on 1 board then I guess I can do large quantity, if they're 3"x5".. then I'll only be able to make a few. Are these boards you want for a stand alone monitoring unit? or a charger you're building?


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## MrAl (Jul 3, 2008)

Hi again Van,

Well, i guess it depends then on what you want to do and how
much you would charge for one board of say 3x5 inches. For
the Monitor chip i would say that size would allow two boards
on one each board being 3x2.5 or something like that. For
a switching regulator (which i guess i could offer myself then)
it might be the same, so one switching regulator with one
Monitor (for example) on the same board would be 3x5 inches 
too i guess.
A friend and i were talking about other things too, most notably
a seven segment LED thermometer...fairly simple, yet we cant
find one we like anywhere for a decent price, so i was thinking
of doing one of these too for us two and maybe offering them
to the general public too at some point. I would say one board
of this kind would be 3x5 or something like that because it
would have two 4 digit displays (hopefully blue LED), one for
indoor and one for outdoor.
Aside from those apps, there would also be some motor controller
boards for stepper motors which connect to the PC for computer
control.
Of course battery chargers...i have yet to design one that does
all three chemistries: LA, NiMH, and Li-ion, which would be
nice so i can get rid of my collection of chargers (ha ha).
I would probably concentrate on the NiMH type first, to make
it a very fast charger (30 minutes for 2500Ah cells, some people
dont like 15 minutes because it weakens the cell somewhat),
and of course 4 bays with computer monitoring. I've wanted
to do this for a long time now but didnt feel like making my
own pc boards. I am talking about very reliable designs too,
ones that would be rated for more than the expected output
current and power so the units last.

So then, i guess the question is, what do you think you would
charge for a 3x5 inch board? Since there are pheno boards
and glass boards i guess a price for each type would be good.
Also, what kind of format can you accept for the drawing, as
i usually make a bitmap (actually gif) file of my artwork.
I have found that some drawing programs let you spec the
size of the drawing before it's printed, so for 3x5 you would
set the aspect ratio to 1 and the width (say) to 5 which isnt
too hard to do. I've gotten exact dimensions this way even
over a span of 5 inches (it looks perfect with a standard drafting
type ruler).


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## VanIsleDSM (Jul 27, 2008)

I could accept any kind of image as long as it's to scale and I can print it out. To make one board I couldn't really do it for less than $20, to make 4 I could do them for $15.

Another update on the springs.. They're taking longer than expected. I checked again at the store and they said they expect them now on Aug 7th. Sorry for the wait everyone.. if I make more of these I'll definitely need to find a better source for springs.​


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## LuxLuthor (Jul 28, 2008)

Van, I have followed your progress and details in this thread with much admiration. Very few will ever know how much time you have put into this project, and it is really great to see how you & other members have addressed so many questions, concerns, and details. Your closeup photos of the circuit work are awsome.

Funny you mention the problem finding an economical source of decent springs. I have run into that same issue making battery cradle holders or battery packs with a built in tailcap spring. I'm not exactly sure which type of spring, but here are some suppliers I found that may be of use:
*http://www.centuryspring.com*
*http://www.acewirespring.com/springs.html*
*http://www.reidsupply.com/results.aspx?Ntt=springs&N=0&Rn=1*
*http://tinyurl.com/6x5vq6*
*http://www.generalwirespring.com/products.asp*
*http://www.fourslide.com/products.htm*​Anyway, thanks again on behalf of the community for everything you are contributing with this project. Although some early comments may have been discouraging, I think they were based in well intentioned safety concerns. You have taught & reminded us that each member (even if new) should be viewed and respected independently.


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## zipplet (Jul 28, 2008)

I'm watching this with interest, as I have had the same idea but didn't realise you were already working on a charger VanIsleDSM. My idea is completely different using a PIC microcontroller but the goal is the same, just I want to allow VERY low charging currents for tiny cells (even as low as 50ma current). However I don't plan to sell anything


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## Dantor (Jul 28, 2008)

yes, thank you VanIsleDSM! very interesting and very cool of you bro :thumbsup:


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## LuxLuthor (Jul 28, 2008)

Van, here was another old custom Li-Ion charger made by AWR with pix.


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## RocketTomato (Aug 5, 2008)

Hi VanIsleDSM,

I was wondering how difficult would it be to incorporate the following into a second version of the charger:

1. An auto-timer shutoff. The timer would vary with the charging rate

2. An LCD display similar to the one on the La Crosse BC-900 which would display charging rate selected, voltage, time elapsed and status.

Thanks and by the way great job on these chargers.


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## VanIsleDSM (Aug 5, 2008)

Thanks Dantor, and Lux, I'm sure those spring links will come in handy.

Zipplet I noticed your thread, The charger here will go down to 100mA charge, but no lower. Good luck with your project.

RocketTomato, there is a safety timer already built into the device. Preconditioning will be terminated if it lasts for more than 3 hours, fast charge will be terminated if it lasts for more than 4.5 hours, and then there is a global timer that will shut down the charger if charging isn't fully complete after 9 hours. I suppose these values could be lowered more, but I wanted to be able to charge larger cells and such without worry.

As for the LCD display, that would be a nice feature, though if the charger is already running off 5VCD from the computer, then I think going the method MrAl has suggested by just plugging the charger into the computer and being able to see what's going on on your monitor would be more cost effective, and more powerful as far as features would go as well.


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## zipplet (Aug 5, 2008)

VanIsleDSM said:


> Zipplet I noticed your thread, The charger here will go down to 100mA charge, but no lower. Good luck with your project.



Thank you and good luck to you too. I especially find the computer interface idea of your charger interesting (I have no intention of doing this) and it could evolve into a lithium ion battery analyser which would be very interesting indeed  I'll keep an eye on this one for sure.




VanIsleDSM said:


> As for the LCD display, that would be a nice feature, though if the charger is already running off 5VCD from the computer, then I think going the method MrAl has suggested by just plugging the charger into the computer and being able to see what's going on on your monitor would be more cost effective, and more powerful as far as features would go as well.



I agree that an LCD display is not needed in this case, however I think you should definately keep the status LEDs you currently have even in the future. It may be tempting to drop them in a future design when you have a computer interface, but don't! I am assuming it will connect via USB?


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## RocketTomato (Aug 5, 2008)

VanIsleDSM said:


> RocketTomato, there is a safety timer already built into the device. Preconditioning will be terminated if it lasts for more than 3 hours, fast charge will be terminated if it lasts for more than 4.5 hours, and then there is a global timer that will shut down the charger if charging isn't fully complete after 9 hours. I suppose these values could be lowered more, but I wanted to be able to charge larger cells and such without worry.



That chip designer thought of everything! Those sound like very reasonable cutoffs assuming you choose your charge current rate wisely based on the capacity of the cell you are trying to energize.



VanIsleDSM said:


> As for the LCD display, that would be a nice feature, though if the charger is already running off 5VCD from the computer, then I think going the method MrAl has suggested by just plugging the charger into the computer and being able to see what's going on on your monitor would be more cost effective, and more powerful as far as features would go as well.


 Yep, I agree that the computer interface would be an ideal option (especially if you are running the charger off your computer P/S) but I was thinking an LCD display would be an easier option to implement since I (naively) assume it would not require any programming.

Have any of you seen this?

http://www.stefanv.com/electronics/battman2.html 

It appears to be a neat DIY charger with a computer interface. The software is open source, so maybe it could be adopted to your charger or at least give you a starting reference for programming the USB interface.


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## Dantor (Aug 26, 2008)

bump for an update?!


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## VanIsleDSM (Aug 27, 2008)

Ok, I've got some good news, and some bad.

First the bad. I've been back into the store twice now to get angry for not having any springs. They keep telling me that they're out east, and they, for some reason, haven't put them on the truck yet. Seems every time I go in, they just tell me "2 more weeks". I'm getting pretty choked with them, and when I build more of these in the future, I will most definitely be redesigning them around a different spring than I can actually get. So when will I have all of the springs? ..beats the hell outta me, 2 weeks hopefully?

Good news. For michelkenny and zapper anyways. When I did go back in the store today, I noticed that there were 5 more of these springs I need on the shelf. Of course when I first saw these I was pretty excited, I thought mine had come in, and some fool put them on the shelf instead of calling me... but 'twas not the case. Nobody seems to know where they came from, one lady figured they may had been returned.

So.. since I have a couple of the springs already, I can get michelkenny's 4 chargers, and zapper's 2 chargers (first 2 people on the list in the thread in the MP) done, probably tomorrow.

For everyone else waiting, I'm terribly sorry. As soon as I have the springs, I'll get the rest of the chargers done ASAP.


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## dom (Aug 27, 2008)

No rush from me Van -just be happy to get some of these in the first place.

I should have asked before -but what are the dimensions of the spring? Might have some as a stock item at one of the engineering shops we use.

Cheers
Dom


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## michelkenny (Aug 27, 2008)

VanIsleDSM said:


> Ok, I've got some good news, and some bad.
> 
> First the bad. I've been back into the store twice now to get angry for not having any springs. They keep telling me that they're out east, and they, for some reason, haven't put them on the truck yet. Seems every time I go in, they just tell me "2 more weeks". I'm getting pretty choked with them, and when I build more of these in the future, I will most definitely be redesigning them around a different spring than I can actually get. So when will I have all of the springs? ..beats the hell outta me, 2 weeks hopefully?
> 
> ...



Do you have a sku number for CT? I can check mine here to see if they have any.


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## VanIsleDSM (Aug 29, 2008)

Pretty much finished the chargers, I was just testing them tonight, all that's left is to epoxy on the heatsinks and they're done. It's always so much more work than expected! A good 4 hours or so on each one of these bays.. not including R&D. Etching boards, soldering, machining PVC, glueing, welding, soldering, machining aluminum, more soldering, more glueing, more soldering, more glueing, more soldering.. wheww!

I did hit a little blip in production. The temp sensing wouldn't work on one of the bays on the 4 bay charger. I suspect it's the cheap thermistors.. I admit, I cheaped out on the thermistors.. they were a more expensive part.. and I spent most of the budget for the cheap charger on the IC chip. I had it all tested before I put the final PCB on, but once it was done, it didn't work. I suppose it could have been the heat from the last solder joint, but I don't know how much eat could have gotten to it from that last joint.. But I can't open it up again now, it's all soldered and epoxied together. It's not a total loss though, I just disabled the temp sensing on that bay and its works fine otherwise.

Silverfox and I had a discussion in another thread somewhere about the relevance of temp sensing for Li-Ion chargers. The only thing I can see is if you leave your charger somewhere that's too hot or cold.. bellow freezing or in your car in the scorching sun. But that's not really going to happen with a battery charger. These charging IC chips are designed for cell phones, PDAs, and digital cameras.. those would be much more likely to be subjected to adverse enviromental conditions during charging. Also.. since you can use these things while charging them, power dissipation in the device can get quite high, and this could overheat the charging process. I may not even include temp sensing in the next QNF batch of chargers I build, we'll see.. I'm going to try charging some improper batteries and such to see if I can get some heat and justify the temp sensing. If I do end up using it on later models, I'll be using a more robust axial or radial type thermistor.

As for the springs, I'll try to find a box somewhere to get the SKU#. Alas I have to stop playing with electronics and LEDs soon... I must return to my real job.. In a couple more weeks I'll be leaving for 6-8 weeks. Regina this time. So.. starting to look like the rest might not happen until I'm back from work.

Info in the MP concerning the sale/shipping.


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## linterno (Oct 14, 2008)

I would like to read comments from any one who has bought and used this charger.

Respectfully.

Juan C.


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## LED Boatguy (Oct 14, 2008)

linterno said:


> I would like to read comments from any one who has bought and used this charger.
> 
> Respectfully.
> 
> Juan C.


 
Ya, me too.

I didn't know about this thread and by happenstance ordered several of those chips (QFN Type) and their components this morning. Nothing like re-inventing the wheel. I'll go back to the board layout and make sure I've got a good heat path. Can you do vias manually? How about cutting out where the metal pad is and mount a (grounded) HS from behind? 

I'm going with a LDO 7805 dinosaur to feed the 1S, not sure about the 2S.

Here is how their demo board is laid out:





Originally tried to do this with a PIC. The code wasn't so bad, but the parts count was out of this world.


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## linterno (Oct 18, 2008)

linterno said:


> I would like to read comments from any one who has bought and used this charger.
> 
> Respectfully.
> 
> Juan C.


Did any one buy and tested this charger?


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## dom (Oct 20, 2008)

2 guys got theirs - check post #4 for the link.

You might PM them for some info.

Cheers
Dom


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## michelkenny (Oct 20, 2008)

dom said:


> 2 guys got theirs - check post #4 for the link.
> 
> You might PM them for some info.
> 
> ...



I was supposed to get mine a while ago but never did...


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## dom (Oct 21, 2008)

Bummer -i was looking forward to mine eventually.
Van must have had to run and missed the postman :-(

Cheers
Dom


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## mynick (Oct 25, 2008)

Hi VanIsleDSM!

I saw your amazing pcb charger for li-ion cell. :thumbsup:

I will do a charger too for myself. With the similar chips, I still have them, it wasn't easy to get the chips here is Hungary. 
May I ask about the type and parameter of the capacitors you use on the board between the battery(cell) +/- connection and the Vin/GND connections?


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## VanIsleDSM (Nov 10, 2008)

Sorry everyone.

I've been away for work and didn't have internet access for a while. I'll probably be home in about 4 weeks. Hopefully the springs will have arrived by then. I've been using a charger here at work quite often, has a lot of charges on it now, and it's working flawlessly other than the thermistor for sensing the battery temperature. One of them on the 6 I recently made didn't work from the start, and now the thermistor on the charger I have here at work has finally failed, but I have deactivated the temp sensing, and it's working fine without.

The solution would be to buy a better thermistor, it was one of the more expensive components, and I chose a cheaper product for this task. I can't afford to buy a better thermistor and still sell them for $10, nor can I take the time to change the configuration of resistors to accept a different thermistor, so I'll be deactivating the temp sensing on all of the chargers. They will still be available.. I know it's taking forever. Damn springs. But I am glad I had the time to figure out the exact problem with the temp sensing.


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## wapkil (Jun 14, 2009)

Hi all,

Without knowing that this thread exists I recently bought the MCP73861 IC (the same one as used here) to build a charger for myself. I was directed here by another CFP-er, TexLite, who shown me that there was already such an interesting discussion about the subject. I'm not planing to build more chargers and sell them (but mdocod wrote he may, so who knows) but I made some tests and posted the results in my thread so if someone's interested you may want to take a look.


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