# Soldering wires to batteries safely?



## MrNaz (Jun 6, 2010)

I am trying to make a 3P2S array of 18650 batteries that needs to fit in a 40mm tube. Working out the geometry of the batteries alone gives me a required tube diameter of 38.8mm, so there's not enough space to use a holder or any sort, so I would like to make a battery pack with heat shrink over a set of 6 batteries like you can buy for R/C cars or the like, only bigger.

My problem is soldering wires to the batteries to ensure good connection once I put the shrink over them. I know that soldering to batteries is a no-no, but surely there are ways to ensure that wires can be permanently attached to batteries without damaging them or putting yourself in danger.

I guess I could buy 18650s with soldering tabs, but they are far more expensive. I can get non-tabbed 18650s from DX for under $4 each. Buying tabbed batteries from batterystation.com or something costs close to $20 per battery.

So I need a way to attach my own tabs or wires to the battery. What is the best way to do this?


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## spencer (Jun 7, 2010)

I tried soldering some NiCADs end to end and they even had tabs but they got too hot and I destroyed them. For a different project I found that the local battery store makes packs. I brought them some cells and for a fairly reasonable price they made a pack for me and they even shrinked it. See if you have a local store with a battery welder.


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## jasonck08 (Jun 8, 2010)

It's hard. I made a 2p3s 18650 pack. I soldered wires from battery to battery. Use lots of flux and make sure your iron is is plenty hot. First tint the wire with plenty of solder, then I think i used my copper hammer head bit to touch the wire to the battery for less then a second. Heat is batteries worst enemy. I think i bought my hammerhead bit from cheapbatterypacks.


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## vestureofblood (Jun 8, 2010)

MrNaz said:


> I am trying to make a 3P2S array of 18650 batteries that needs to fit in a 40mm tube. Working out the geometry of the batteries alone gives me a required tube diameter of 38.8mm, so there's not enough space to use a holder or any sort, so I would like to make a battery pack with heat shrink over a set of 6 batteries like you can buy for R/C cars or the like, only bigger.
> 
> My problem is soldering wires to the batteries to ensure good connection once I put the shrink over them. I know that soldering to batteries is a no-no, but surely there are ways to ensure that wires can be permanently attached to batteries without damaging them or putting yourself in danger.
> 
> ...


 
Hi MrNaz,

First I would like to say that I have only done this with NIMH cells, but it can be done.

A couple of things you may already know but I feel the need to mention. In order to charge this pack properly you will need to have a charger that will balance the voltage of the individual cells during the cycle or install something called balance tabs or taps ( dont recall) to the ends of the cells.

That being said. In order to do this you need to go very hot very fast. What I mean is if your iron is not hot enough to melt the solder in about 1 second or less, you will begin to heat up the cell internaly which is very bad.

I use flux for each connection, tin each end of the cell, reapply flux if needed and then solder them together. I dont use wire in between the cells, accept at the ends, you could use that or a thin strip of copper. 

Again the most important thing ( other than charging safety for the pack) is you must have a hot iron so only the surface of the cell gets the heat.

Get some flux and use it. Apply it to the cell and to the wire, tin them both and then add more flux. Make the connections and then take a cue tip with some alcohol on it and clean the connections. Flux is an acid that can weaken the joint later if not removed. 

Good luck with your build, and please be careful.


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## PeaceOfMind (Jun 8, 2010)

I've done this successfully with Li-Ion cells before using this procedure:
a)Solder extremely quickly
b)Immediately upon removing the soldering iron, have a second person cool the cell with a damp cloth by dabbing the newly soldered area

Be careful not to short the cell by getting it too wet. In fact, if you have some distilled water that would be highly recommended. And this is definitely a two person job - someone quick with the soldering iron to solder and someone right there ready to cool the cell off. If you fail to make the solder joint properly in a second or two, cool the cell and wait before trying again.

I've done this successfully literally hundreds of times as a two man team in order to build very large li-ion packs (not flashlight related). However I take no responsibility if it doesn't work for you!

Good luck!


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## MrNaz (Jun 8, 2010)

I found a better way! Although, it will require a whole side project to make the capacitive welder...

http://www.rcgroups.com/forums/showthread.php?t=763308

That seems to be the best way I've found, and I've done quite a bit of looking since I posted the original question.

Thoughts?


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## kramer5150 (Jun 8, 2010)

Heres a partial re-post from an earlier thread...

Soldering bus bars onto cells is not the most straightforward thing. You are going to need a good soldering iron (a station would be ideal), one that can maintain its temperature when it contacts the cell. Cells are heatsinks, and will "freeze" your iron tip when the two come in contact, unless your iron can sustain its own temperature enough to allow the solder to flow. I use at least an 80 watt weller pencil iron, and it has worked fine for my RC hobbies. The hotter, the better... but then again its paramount that the iron has th ability to maintain and sustain its temperature. The generic "pencil" tips that are OEM for most irons and stations will not work very well. I have always found the more blunt tips with flats on them to work best... pic here.






Cell surface preparation is paramount. Iso-propyl alcohol (99% will suffice) , some firm scrubbing, flux application to the area. You can use a dremel ball grind attachment to scuff the surface, but I have not found this to be necessary all the time. A seasoned RC heli enthusiast once told me that solder flows where flux goes. So a little flux goes a long way to ensure good solder contact.

Deans battery bars and 12AWG wet noodle are pictured. I have seen guys make their own battery bars using tinned copper stock, cut to shape.


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## spencer (Jun 8, 2010)

So I grabbed some dead AA alkies, set my Hakko station to 900F and I had decent results. As mentioned earlier in this thread you have to (in this order) flux, tin, flux, then solder. You must do this to both your battery and wire. Using this method I was able to solder batteries end to end as well. Good luck, get a decent station, get some flux, and maybe practice on some dead cells first.


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## MrNaz (Jun 9, 2010)

This is OK for joining batteries that are not end to end, but if one was to heat shrink batteries in series, how would you go about ensuring that the end to end connection was maintained? Is there a way to join these easily? Is there a conductive paste that you can use to ensure that a good connection is maintained?
- Naz.


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## Th232 (Jun 9, 2010)

Same method as Kramer reposted, then fold the metal strip after soldering?


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## e1sbaer (Jun 9, 2010)

Let me start to say I'm no expert on batteries.
That said, I did solder a tip on top of an 18650 battery which holds really well. 
When soldering electronics like computer chips you have to use an soldering iron of low wattage (and thin solder) so not to ruin the electronics by too much heat. I use an 11 Watt soldering iron for that and that's the one I used to solder the tip. When the iron is heated up, you heat the battery (+ of -) top. Ideally the solder would never touch the soldering iron but would go fluid when it touches the surface you're heating. With a battery you won't get that done with 11 Watt and it probably wouldn't be wise. So I heated the top for 10 seconds or so and then applied the solder at the point where the soldering iron heated the top. The battery was less warm then it is when being charged and the soldered tip is quite solid.
I think it's safe to do it this way and haven't noticed any problems, but anyone feel free to correct.


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## 65535 (Jun 9, 2010)

When soldering batteries you'll absolutely want at least a 50W iron, preferably more towards 65-85W. The key is to get the job done FAST. So get the tip heavily tinned and use plenty of solder to transfer heat to the surface you want to solder, have everything ready and tinned. 

Personally I tin the wire with a bit more than I normally use for connections, heat the battery surface adding excess solder to improve thermal conductivity, once everything is wetted solder the wire onto the surface and let cool. This should not even take 10 seconds from heating to done.


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## vestureofblood (Jun 10, 2010)

MrNaz said:


> This is OK for joining batteries that are not end to end, but if one was to heat shrink batteries in series, how would you go about ensuring that the end to end connection was maintained? Is there a way to join these easily? Is there a conductive paste that you can use to ensure that a good connection is maintained?
> - Naz.


 
If you are wanting to join the cells in series here is a great vid on doing that.

Also post #38 in this thread will help.


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## MrNaz (Jun 10, 2010)

e1sbaer said:


> Let me start to say I'm no expert on batteries.
> That said, I did solder a tip on top of an 18650 battery which holds really well.
> When soldering electronics like computer chips you have to use an soldering iron of low wattage (and thin solder) so not to ruin the electronics by too much heat. I use an 11 Watt soldering iron for that and that's the one I used to solder the tip. When the iron is heated up, you heat the battery (+ of -) top. Ideally the solder would never touch the soldering iron but would go fluid when it touches the surface you're heating. With a battery you won't get that done with 11 Watt and it probably wouldn't be wise. So I heated the top for 10 seconds or so and then applied the solder at the point where the soldering iron heated the top. The battery was less warm then it is when being charged and the soldered tip is quite solid.
> I think it's safe to do it this way and haven't noticed any problems, but anyone feel free to correct.



I appreciate your help, but I just have to say that this advice is wrong. 

You have to use a very high wattage iron to ensure minimum thermal energy is transferred in by keeping contact as short as possible. Furthermore, if you heat the battery terminal enough such that solder melts onto it, you're heating up the internals enough to degrate the electrolyte and will greatly reduce battery capacity.


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## MrNaz (Jun 10, 2010)

OK I think I've found the best way to do this: Electrically conductive epoxy.
http://www.epoxies.com/elec.htm
The 40-3900 product looks like exactly what I'm after. It may even be suitable for use instead of welding the battery bus strips.

I'm sure there are many projects here that could benefit from this stuff, so spread the word!


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## e1sbaer (Jun 10, 2010)

MrNaz said:


> I appreciate your help, but I just have to say that this advice is wrong.
> 
> You have to use a very high wattage iron to ensure minimum thermal energy is transferred in by keeping contact as short as possible. Furthermore, if you heat the battery terminal enough such that solder melts onto it, you're heating up the internals enough to degrate the electrolyte and will greatly reduce battery capacity.



Yes, that's why I said that in case of a battery it's probably not wise to let the solder melt (on the battery terminal). About the wattage, I'll use a higher wattage for batteries next time. That's why I like this forum


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## LukeA (Jun 10, 2010)

MrNaz said:


> I found a better way! Although, it will require a whole side project to make the capacitive welder...
> 
> http://www.rcgroups.com/forums/showthread.php?t=763308
> 
> ...



That stuff's massively more resistive than solder or wire.


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## wquiles (Jun 10, 2010)

Besides having enough heat to solder the cells quickly and safely, the real "key" is the the flux, and just not any flux:
Kester Flux pen - Type 2331 

and this solder has the same flux built-in:
331 Kester Solder

Will


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## kramer5150 (Jun 10, 2010)

MrNaz said:


> I appreciate your help, but I just have to say that this advice is wrong.
> 
> You have to use a very high wattage iron to ensure minimum thermal energy is transferred in by keeping contact as short as possible. Furthermore, if you heat the battery terminal enough such that solder melts onto it, you're heating up the internals enough to degrate the electrolyte and will greatly reduce battery capacity.



this advice is correct... you want the iron to be HOT (80-120W) in order to limit exposing the cell chemistry to heat. The longer the cell is exposed to heat, the more at risk it is of damage. Using an 80-120 watt blunt tip weller pencil, the longest I need to hold the iron onto the cell is ~3-4 seconds. You shouldn't need to pre-heat the cell, and you definitely do not want to hold the iron onto the cell any longer than what it takes to flow the solder. 

The other thing I do is use a damp sponge to cool the solder joint down and prevent the further spread of heat into the cell. The solder will solidify but retain a lot of heat after the iron is removed. You want to eliminate this heat source quickly before it enters further into the cell.

Its like searing a steak on the BBQ grill. You want to sear/brown and alter the chemistry of the outside without adversely affecting the chemistry inside.


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## chefgrill (Jun 10, 2010)

This is how I've done it:

1. Use a dremel, or similar to roughen the contacts.
2. Secure the cells, you only have two hands. 
3. Use a good Soldering iron, add some solder to the ends, it should flow by itself.
4. Add whatever you prefer to connect the cells to each other.

As others said, keep the thermal stress as low as possible, practice on some old NiCD's, they won't explode.

As also mentioned before, you'll need to balance while charging, therefore, you need a charger which has a balancer, or an external balancer.

You need extra cables and an appropriate connector for the balancer. Pin 1 goes to ground, Pin 2 goes to + from Cell 1, Pn 3 goes to + from Cell 2, and so on.

I'll do a quick guide on this, as soon as I find the time, but don't wait for me.


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## MrNaz (Jun 10, 2010)

chefgrill said:


> As also mentioned before, you'll need to balance while charging, therefore, you need a charger which has a balancer, or an external balancer.



Cant you charge them all at once as a single pack? I.e., charge them in parallel the same way that you apply load to them in parallel?


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## chefgrill (Jun 11, 2010)

You can charge them in parallel, but you'll have to make sure, that they are more or less balanced, before connecting them parallel.

But if you want to do so, You'll have to remove the serial connection first, otherwise you'll create one big short circuit.

Additional Info:
http://www.rcgroups.com/forums/showthread.php?t=599316
http://scriptasylum.com/rc_speed/_lipo.html


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## MrNaz (Jun 11, 2010)

chefgrill said:


> You can charge them in parallel, but you'll have to make sure, that they are more or less balanced, before connecting them parallel.



I understand that, and I understand why. I will charge them all fully from the same charger before, and verify with a multimeter that they are at the same voltage before connecting them in parallel.

I'm a bit concerned about the need to *keep* the batteries balanced. I actually plan to pot the batteries into one huge integrated piece for ruggedness. I'll assemble them first, holding all the circuitry in place with blobs of epoxy, and then sink the whole thing into a cylinder of resin, leaving only a single 2.1mm DC socket exposed for load and charger connection. Thus, batteries will not be able to be disassembled later for re-balancing.

As long as they are balanced to start with, they should remain so given that they are all connected together right? Even if one series stick becomes over or under charged, the voltages will always tend towards becoming balanced when the load or charger is disconnected, right?


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## vestureofblood (Jun 12, 2010)

MrNaz said:


> Cant you charge them all at once as a single pack? I.e., charge them in parallel the same way that you apply load to them in parallel?


 



MrNaz said:


> I'm a bit concerned about the need to *keep* the batteries balanced. I actually plan to pot the batteries into one huge integrated piece for ruggedness. I'll assemble them first, holding all the circuitry in place with blobs of epoxy, and then sink the whole thing into a cylinder of resin, leaving only a single 2.1mm DC socket exposed for load and charger connection. Thus, batteries will not be able to be disassembled later for re-balancing.
> 
> As long as they are balanced to start with, they should remain so given that they are all connected together right? Even if one series stick becomes over or under charged, the voltages will always tend towards becoming balanced when the load or charger is disconnected, right?


 
It seems to me the problem isnt the parallel part of your pack. In your original post you mentioned wanting to make a 3p2s pack. Theoretically if one of our cells in a 3P pack was charged higher than another the charge would terminate early when the first cell reached 4.2V there by giving a slight decrease in capacity. 

However if your pack is 3P2S ie a 7.4V pack this could be a problem. Lets take a 2 cell series pack for example. When the first cell (or parallel 3 pack) is charged to a full 4.2V, if the second cell or pack in series has gotten out of balance say only 3.8V, and your chargers goal is 8.4 it could continue charging until the total voltage of the pack reaches 8.4 ie leaving the first cell at 4.4V and the second at 4.0 when the charge terminates.


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## MrNaz (Jun 12, 2010)

vestureofblood said:


> However if your pack is 3P2S ie a 7.4V pack this could be a problem. Lets take a 2 cell series pack for example. When the first cell (or parallel 3 pack) is charged to a full 4.2V, if the second cell or pack in series has gotten out of balance say only 3.8V, and your chargers goal is 8.4 it could continue charging until the total voltage of the pack reaches 8.4 ie leaving the first cell at 4.4V and the second at 4.0 when the charge terminates.


Is that really a risk with series charging? I though that evening out the voltages is the reason that the chargers drop the voltage difference between Vbatt and Vchg as the charge continues.

Or do I misunderstand, and this is really a big risk of in-series charging?


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## vestureofblood (Jun 12, 2010)

MrNaz said:


> Is that really a risk with series charging? I though that evening out the voltages is the reason that the chargers drop the voltage difference between Vbatt and Vchg as the charge continues.
> 
> Or do I misunderstand, and this is really a big risk of in-series charging?


 
I dont build li-ion packs, so I am no expert, but I dont see many people doing it without some sort of balancer in place. Some times what is "advisable" and what is "doable" are two different things, but in this case I am not sure the risk is worth it. 

Here is another thread similar to yours where balance tabs are mentioned.

If you search "battery pack building" on CPF all of the threads about series packs of li-ion mention using those or similar methods.

Your pack is certainly something that can be done, but seems to me like adding a little extra protection in the pack, and finding the correct charger would be a good idea. Just my 2 cents.


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## chefgrill (Jun 13, 2010)

vestureofblood said:


> Lets take a 2 cell series pack for example. When the first cell (or parallel 3 pack) is charged to a full 4.2V, if the second cell or pack in series has gotten out of balance say only 3.8V, and your chargers goal is 8.4 it could continue charging until the total voltage of the pack reaches 8.4 ie leaving the first cell at 4.4V and the second at 4.0 when the charge terminates.



That's exactly what it is about, and that's why balancing is a must.

MrNaz, you only need one additional contact (which is between the two parallel packs), maybe you could just add an additional connector for this?

Or you could include a balancer within your battery pack, but I don't know if there are balancers which can be connected while discharging.


btw, I'd like to see some pictures of your finished pack, I've never worked with resin.


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## VidPro (Jun 13, 2010)

i can get Tabbed LG 18650s for about $9 everytime. $20 is to much, look around, also your $4 ultrafire thingeee isnt going to be worth the time you put into building it. for the long run a good REAL Lg cell or sony or something will outlast a UltraThing by 3X. i percieve (imo) your assesment of the total costs over time are missing major points.
and dont forget about putting in the balance connections especially if your going to use ultrajunk.

yes you can solder, you dont even need tabs, and you dont need to do crasy stuff, flatten copper wire with a hammer, tin everything, and do the foldover , not only is that method practical, but its removable TOO.
i dont like the lockdown battery to battery method for all the reasons, it is unbendable, it is impossible to undo, and you cant get to the areas (you soldered to) to apply cooling.
I use Much and Much Heat FAST (as was said) and ice (as needed) for cooldown.

it not so much the "watts" of the solder heater, but the Core of the soldering gun that helps (me) a lot, but you need a lot of heat Fast and you want to be done in less than a second, and everything should be prepped.
See the big FAT solder tip/core pictures above, having a large "core" tip. The tip and core Hold a lot of heat and get heat transfer to occur immediataly keeping heat out of the internals of the cells.
as soon as you touch any of these heaters to a cold hunk of metal the tip gets cooled, with a good core/tip it holds enough heat to keep the heat going.
so in reality a 40W heater with a big fat pre-heated core works, and a 220W gun thing with a little weasily tip doesnt. I found it isnt Just about watts. 

if this link works
http://www.sears.com/shc/s/search_10153_12605?keyword=soldering+gun&vName=&viewType=24&viewItems=24
see the "*Craftsman Professional Dual Heat Soldering Gun*"
see how it has a Mondo Core , that holds and transfers heat without the tip cooling, gets it done in seconds.
then
right next to it the things like the high wattage "Weller" styles, with the extreeme wattage but the small tip and no actual "core" those things suck and always gave me troubles, they "work" and have the power and heat, but for speed its all about the big Pencil core thing.

so when finding the right tool, get the one that can transfer loads of heat and work fast, not the one thats all talk of watts


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## Illum (Jun 13, 2010)

could soldering wires to 0.18x0.18x0.08" rare earth magnets from the side and then tack them on the batteries work?

Without involving spotwelders thats the only method I can think of that minimizes thermal shock


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## MrNaz (Jun 13, 2010)

VidPro said:


> i can get Tabbed LG 18650s for about $9 everytime. $20 is to much, look around, also your $4 ultrafire thingeee isnt going to be worth the time you put into building it. for the long run a good REAL Lg cell or sony or something will outlast a UltraThing by 3X. i percieve (imo) your assesment of the total costs over time are missing major points.
> and dont forget about putting in the balance connections especially if your going to use ultrajunk.


Can you point me at some suppliers for LG or Sony cells? I haven't been able to find a supplier of cheap batteries that doesn't charge an arm and a leg. I'm happy to buy in bulk, each pack requires 6 cells, so buying 30 or so would be fine.


VidPro said:


> yes you can solder, you dont even need tabs, and you dont need to do crasy stuff, flatten copper wire with a hammer, tin everything, and do the foldover , not only is that method practical, but its removable TOO.


I'm just not game to solder batteries. Also, if you see my post above, I've found electrically conductive epoxy. I'll test its resistance, but it wouldn't be much of an issue, it'd just be there to augment contact between the battery terminals in series, and hold them in place. I've been assured by the manufacturer that conductivity is high though.

If I can get pre-tabbed batteries, great. If not, I'm going to try to build the capacitive discharge welder I linked to earlier in this thread. It'll probably take a few days and a couple hundred dollars in parts, but I'm sure it'll be worth it if I'm going to be making packs more often.

But please, point me at your supplier of $9 LG cells. I recently bought 20 TrustFire 18650 unprotected cells from DX. I got them at $2.80/cell. You're probably right that they'll be craptastic. But given that I'm probably going to blow the first few packs I make, I'd rather it be with cheap cells than expensive ones. So I'm definitely interested in finding out where I can get good cells from at a decent price.


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## VidPro (Jun 13, 2010)

i dont know why the real LG are so elusive, one day batteryjunction will carry them, then batteryspace , then i have to get them on e-bay, and each time i have to make sure that i am not getting frauded (i dont care who is selling them). 
this week seems like they are here ??
http://www.all-battery.com/LGli-ion1865037v2600mahrechargeablebattery39035.aspx

who knows. someday i was thinking i would have to buy OEM sony battery packs to get really good cells and be SURE they really are.

i dont know where. it always changes, but e-bay often has reliable sellers selling them tabbed and not tabbed, but then again e-bay can also have pitfalls and potholes galore.

when you make your welder make it a dang good one, i have seen tabs that were put on with some cheap knockoff stuff and one twist and the welds break. just wasnt good enough, or wasnt being used by the right person.


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## VidPro (Jun 13, 2010)

oh tabs here is the same people doing tabbed.
http://cgi.ebay.com/6-LG-Chem-3-7V-...tem&pt=LH_DefaultDomain_0&hash=item5ad3f83f22


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## MrNaz (Jun 14, 2010)

So how do I wire up a 2S3P battery pack such that the cells are balanced? Do I have to isolate each of the 6 batteries? Or just the 2 parallel segments? Or is it the 3 series sticks?

Any advice on constructing a battery pack that can be balanced would be great!


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## ronkar (Jun 15, 2010)

Battery pack wiring instructions. Plug in 2s and 3p values in the boxes and check the show balance wire hookup. It gives you an easy to read diagram.

http://scriptasylum.com/rc_speed/_lipo.html


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## LuxLuthor (Jun 16, 2010)

From all that I have read, I would never solder Li-Ion cells, but if someone HAD to solder them, I would at least recommend a "safe" chemistry Lithium Manganese or Lithium Iron Oxide. Those that claim they have soldered Li-Ion's do not know what the parts under the metal caps look like, particular the plastic separator and pressure release parts.

I have soldered NiMH packs using a magnetic battery holding jig, and a 70-80 Watt iron and "Hammerhead tip," and with practice you can learn to do it well.

Eventually I bought one of the last 'affordable' Sunstone Engineering single phase battery pack capactive welders, before they jacked up the minimum price for low end model. I have made many hundreds of packs, including at least 50 Li-Ion packs, including with balancing tap leads.

You are correct that Li-Ion packs can be charged and discharged in parallel, but once you make a pack with 2 or more in series (even if it is 2s sets of 6p), you need to balance charge each set of parallel cells to the next set in series. You can monitor them with a DMM to see how each set of cells in parallel behave if you must charge them in series, but ideally it is worth the time to do it right and install balance taps.

If your only option is to get cells with taps, and solder to the taps, I would highly recommend that, even knowing it is more expensive. There is no company that will EVER solder directly to a Li-Ion. Custom users may do it, but again, they have no idea what heat related damage is lurking under the caps.


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## MrNaz (Jun 16, 2010)

LuxLuthor said:


> From all that I have read, I would never solder Li-Ion cells, but if someone HAD to solder them, I would at least recommend a "safe" chemistry Lithium Manganese or Lithium Iron Oxide. Those that claim they have soldered Li-Ion's do not know what the parts under the metal caps look like, particular the plastic separator and pressure release parts.


Yea, I've already decided that eveyrone who advised me to solder LiIons are not to be listened to. There are two options, a) CD welding b) electrically conductive epoxy. Both would achieve the needed result without damaging the battery. I will not be soldering, given that I have options.


LuxLuthor said:


> Eventually I bought one of the last 'affordable' Sunstone Engineering single phase battery pack capactive welders, before they jacked up the minimum price for low end model. I have made many hundreds of packs, including at least 50 Li-Ion packs, including with balancing tap leads.


I need something like that. Where can I get one? How much are they currently? Where do you live so I can break in and steal yours? 


LuxLuthor said:


> If your only option is to get cells with taps, and solder to the taps, I would highly recommend that, even knowing it is more expensive. There is no company that will EVER solder directly to a Li-Ion. Custom users may do it, but again, they have no idea what heat related damage is lurking under the caps.


I've found out that making a third terminal for the balancing charger is pretty easy, and will be doing that. The challenge is going to be finding a reasonable quality charger that's cheap enough to ship with the product :thinking:


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## MrNaz (Jun 16, 2010)

ronkar said:


> Battery pack wiring instructions. Plug in 2s and 3p values in the boxes and check the show balance wire hookup. It gives you an easy to read diagram.
> 
> http://scriptasylum.com/rc_speed/_lipo.html



That's awesome!
Ok, so for a 2S3P cell, what kind of charger would I need? I've seen a few on DX, but when I make the pack, what kind of connector should I connect to the three wires? Is there a standard way to wire them? Is there a standard plug for balanced battery packs and chargers?


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## vestureofblood (Jun 16, 2010)

LuxLuthor said:


> I have made many hundreds of packs, including at least 50 Li-Ion packs, including with balancing tap leads.


 
Lux, if you dont mind could you elaborate on these taps? Where did you get them? Do you wire the leads all in parallel, or in series like the batteries?


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## VidPro (Jun 18, 2010)

MrNaz said:


> That's awesome!
> Ok, so for a 2S3P cell, what kind of charger would I need? I've seen a few on DX, but when I make the pack, what kind of connector should I connect to the three wires? Is there a standard way to wire them? Is there a standard plug for balanced battery packs and chargers?


 
you want to get the charger first Sort of, then you will know what type of balance charge connection would go on the pack item.
if your talking cheap, the turnegy or mystery type hobby chargers are cheap and barely enough to do the job at $30-60.
balance connection wiring is now available at the hobby places and on e-bay. it plugs into the hobby charger thing as an *additional *connection ALTHOUGH you can make a single connection with just the balance connection if you wire it that way (only way to understand this is to see how they work that via the charger).


i will try and fill you in as best as i can.

hobby charger has the main connects (for charge and discharge with or without balancing)
+ and -

Balance connector has all the connections the + and - and the interconnections for Each series cell item.
so a 3 P has 4 wires
the main + the -&+ the -&+ and the -

+|{====]{====]{====]|-
+|{====]{====]{====]|-
Main charge connections

+|{====]|{====]|{====]|-
+|{====]|{====]|{====]|-
..|..........|..........|..........|
+|.........-|+.......-|+........|-
Balance connections
WHICH include the ends See ?


Because these things are used for high power RC stuff, they have BOTH the main pack connection AND the seperated balance connection for balancing.
but the "main" connection is connected along WITH the balance connection, so you have to wire Both AT THE CHARGER. (you see RC peoples might charge at rates the balance connector only wouldnt handle, so they have both)
when used with minor charge rates and all, the mains can be potentially Tapped off the balance plug SOO only one plug item is neded for charging (the one balance plug).
THEN
at the charger itself you tie in the main end connections so you can get away with one plug item.

lol, its much simple, but hard to explain. so you will understand that after you see the charger itself. the wire/connections are color coded and linear in arrangement.

it really is a Piece of cake, and well worth it, and the connections are not large or cumbersome or problematic .

You are looking for a 4pin type of balance connection which will be called 3S , and will be reguardless of the quantity of parellel.
each SET of parellel will be treated to proper voltages during charge as long as each PARELLEL Set (which acts like one big battery) is balanced within the series pack.

so a Web (ebay say) search for that is "li-poly Balance connection 3S" spelled correctally of course , not like i do


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## MrNaz (Jun 18, 2010)

OK so I've got it. You need to get the batteries wired up with a connector to each parallel set. I.e., you need n+1 connectors, where n is the number of batteries. That is OK, I can wire that, no problem.

Now I need to find a charger. Does anyone know if any of the following chargers look suitable:

http://www.alibaba.com/product-gs/271048973/balance_charger_PP301.html
http://www.alibaba.com/product-gs/281296217/2_3_cell_Lipo_battery_balance.html
http://www.alibaba.com/product-gs/279349467/RC_battery_balance_charger_IMAX_B3.html

They all seem to charge 2S battery packs.

Can any Li-Poly charger also charge Li-Ion battery packs, or does each lithium type cell need its own special type of charger?


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## spencer (Jun 19, 2010)

I wouldn't buy anything that cheap when it comes to charging Li-ions. Maybe I'm paranoid but a charger that doesn't work right can make a pack of 6x18650's go BIG BOOM really fast. Burn your house down big boom.

Any charger that charges Lipo will also charge Li-ion.


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## MrNaz (Jun 19, 2010)

spencer said:


> I wouldn't buy anything that cheap when it comes to charging Li-ions. Maybe I'm paranoid but a charger that doesn't work right can make a pack of 6x18650's go BIG BOOM really fast. Burn your house down big boom.


Fair enough. Can you recommend some chargers? Bear in mind that these will need to be packaged with a product for sale, so they can't be too expensive.


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## chefgrill (Jun 21, 2010)

MrNaz said:


> Fair enough. Can you recommend some chargers? Bear in mind that these will need to be packaged with a product for sale, so they can't be too expensive.



If you really want to sell this as a product, I think there should be some additional safety features (temperature, overdischarge, overcharge). What will you do if this thing burns down (and maybe a customer's house too)?


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## MrNaz (Jun 21, 2010)

chefgrill said:


> If you really want to sell this as a product, I think there should be some additional safety features (temperature, overdischarge, overcharge). What will you do if this thing burns down (and maybe a customer's house too)?



Well, just by having a balance charger it's already better than many of the lights sold by other big brands which just sell with 7.4V chargers.

Honestly, how much of a risk is a violent cell failure, in reality? I see this warning thrown around all the time, but other than the Sony laptop issue a while ago, there have been no hazardous situations caused by Li-Ion batteries. Li-Ion batteries are included in literally millions of products these days, from cell phones to laptops to power tools to flashlights and they seem to be quite fine.

Sure, if they are deliberately mishandled, they can fail, but when using high quality batteries (I'll be using those sweet Panasonic 2.9Ah ones) you can also add to the risk assessment that they are designed for safety with venting valves to prevent explosion.

My laptop has 4x 18650 cells in it, and I don't get all aflutter whenever I put it 3 inches from my gonads.

Is there anyone who is actually qualified to say something about the real-world risk associated with Li-Ion batteries? Would selling a 2S3P array with a balance charger like the one mentioned pose a real risk to an end user?


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## 1 what (Jun 21, 2010)

Hi MrNaz.
Have you found a source of the 40-3900 epoxy in Australia?


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## chefgrill (Jun 22, 2010)

MrNaz

I see your point, but if you've ever opened a laptop battery, you would know that there's actually a thermal fuse, and some other protection inside. I'm not an expert, but I understand, that there are risks, those should be minimized, especially on a commercial product.


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## MrNaz (Jun 22, 2010)

1 what said:


> Hi MrNaz.
> Have you found a source of the 40-3900 epoxy in Australia?


No, but I have some I ordered from the manufacturer that is far more than I need and I would be happy to share it with you. The manufacturer says that there are no solvents in either part of the epoxy, so exposing it to the air should not be a problem. They say the shelf life is 12 months officially, but that if it is stored in a cool, dry place and not left open for too long it really should last longer.

Let me know if you want some. I can try to suck it into syringes for you.


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## 1 what (Jun 22, 2010)

Thanks MrNaz.
PM sent.


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