# protected 18650 in series safe?



## VegasF6 (May 14, 2008)

I am wanting to drive a Q5 from 2x18650 batteries, not really wanting to buy AW's at this time. Will be either ultrafire, LG, or perhaps tenergy. I have been looking at cells and circuits for pack building from several places, and I notice that all the protected cells with internal PCB say NOT to pack build with these. 
Here is a link to just one example:
http://www.batteryjunction.com/li18322mahre.html
I already own a 2x18650 light that I am running ultrafires in, to the best of my knowledge with no adverse effects.

To safely do this will I need a driver board that has a low voltage protection built in? Or, will I have to build a pack with a protection circuit for 2 cells, like one of these?
http://www.batteryspace.com/index.asp?PageAction=PRODSEARCH&txtSearch=protection+circuit

http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=2771

So, I can only guess with the built in PCB's they are claiming because they are set for 2.5 volts, they would be useless in a series circuit as the last (or first) battery in the circuit is actually passing voltage from both batteries, therefore the low voltage kick in would be useless?

On, and on a related note, that would not be the case for 2x18650 parallel?

I have looked at some of the ROP LE's and never seen this mentioned before.

It would SEEM as long as the 2 batteries are somewhat balanced before running them it would never be a problem, but perhaps it would be because the internal resistance of each cell varies?


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## LuxLuthor (May 15, 2008)

Those are some good questions. The individual cell PCB (see my photos of taking one apart here) only controls the activity within that one cell, so if you have two in series...and one drops below 2.5V, it will break the circuit, but the other cell may still be above its own PCB.

I have made packs with AW protected Li-Ions. I suspect this is more of a physical/crush/welding-heat or welding-voltage zap concern. You would not want to add another separate PCB circuit to cells that have their own PCB though. 

No problem using Li-Ions in series and parallel in general, as long as you are aware of keeping their voltages balanced if any are in series. In parallel, there is automatic balancing of those cells. Over time cells in series can get out of balance, and a simple series charger only reads total pack voltage...so if you have 1 cell with voltage of 3.7V and other with 4.1V, the charger will see that as a 7.8V 2s pack that it wants to charge up to 8.4V. 

While the overcharge protection cutoff of individual cell PCB's will hopefully break circuit if high cell gets above 4.25V, that assumes you have a quality brand cell and quality brand PCB. I don't regard the non-AW cheap brands you mentioned as having a reliable track record.

When it comes to Lithium Cobalt Ion cells, it is one of the few things in flashaholism that is not worth doing on the cheap. Personally, if you gave me those 3 brands for free (and throw in Trustfire for good measure), I would throw them all away.


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## mikeh (May 16, 2008)

simple answer: 
its fine to use protected cells in series, so long as you charge them individually. A normal twin-cell charger will do this, and has LEDs for each cell.


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## VegasF6 (May 16, 2008)

Well, let me point out a theoritical case. You have 2 cells, the front one drains much faster for some reason, it's internal voltage drops down to 2.0 volts. The rear cell has an internal voltage of 3.0. The protection circuit of the front battery wouldn't trip even though it's internal voltage is low, because it senses the voltage from the other battery passing through it. It isn't smart enough to know where that power is coming from. 

Now, you shut off the light. At this point you have 2 dangerously unbalanced batteries that attempt to balance each other. This doesn't happen instantly, it would take some time. Because the first battery has discharged so low, it is permanently damaged, but you may not realize this until next time you attempt to fire the light. Or, if not then, then when you remove the cells to charge. Hopefully yes, in a 2 channel charger, not with a series pack charger. 

I guess for this to happen the front cell would have to already have some serious problems. I admit I am not really up on battery technology, I don't understand how to measure resistance through a cell, or how it even changes. That's why I came here to the pro's 

So, in practice, it probably isn't anything to actually be concerned with, but in theory I don't think it is something to take for granted that it would never happen. 

Does this theory hold water, or am I missing something and this is physicaly impossible? It's just when I saw the warnings from several battery retailers about which cells are, and are not designed for pack building it got me thinking. 

And finally, LuxLuthor, I especialy admire your opinion and take you as THE authority on such matters, so thank you for weighing in. I will have to seriously re-evaluate my priorities. It is just so easy to fall into the trap of "Hmm, I could buy 8 of AW's 18650's, or I could buy 8 of another brand AND 2 or 3 more flashlights." But, that is a false economy if one of them blows up on me!


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## SemiMan (May 16, 2008)

I don't think your theoretical case works. If one cell is truly internally at 2 volts, then that is what the protection circuit will measure in a series configuration since it connects to the positive and negative terminals of only that battery.... and since you have stated it is 2V, it should cut off. The 3V does not pass through it, it just adds to it. 

In many ways having several protected batteries in series and charging them EXTERNALLY is like having a protected pack. In a good protected pack each battery may be seperately monitored on discharge and for charge the charge balancing makes sure they are equal just like and external charger would do.

I have used protected cells in series without any issues... but I will qualify that with "yet".

Semiman



VegasF6 said:


> Well, let me point out a theoritical case. You have 2 cells, the front one drains much faster for some reason, it's internal voltage drops down to 2.0 volts. The rear cell has an internal voltage of 3.0. The protection circuit of the front battery wouldn't trip even though it's internal voltage is low, because it senses the voltage from the other battery passing through it. It isn't smart enough to know where that power is coming from.
> 
> Now, you shut off the light. At this point you have 2 dangerously unbalanced batteries that attempt to balance each other. This doesn't happen instantly, it would take some time. Because the first battery has discharged so low, it is permanently damaged, but you may not realize this until next time you attempt to fire the light. Or, if not then, then when you remove the cells to charge. Hopefully yes, in a 2 channel charger, not with a series pack charger.
> 
> ...


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## ifor powell (May 16, 2008)

In series I don't see any problem. I have run a pack like this and taken it down to a level where one cell triped and I was throwen into darkness. Once the cells were rechared everything was all OK though.

In parallel I am not quite so sure, at some point coming down the voltage one of the cells will have it's cutoff go and effectivly go open circute. I am not sure whether you can then get a state where the other stronger cell pulls the circute up to the extent that the first cell see itself as being charged and re-activates. Any thoughts? Or should I do the exagirated experiment with my no longer used 18650 and 14500 made to work together?

After that there is the parallel and serial case where again a single cell going down could be even more interesting. I realy would like to know what happens here as it's a configuration I actualy use but at the moment I am carfull not to get anywhere near the cutoff voltages and I monitor the end points after each usage to check the cells are still relativly balanced.

Ifor


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## LuxLuthor (May 16, 2008)

Vegas, again, I understand where you are coming from...and there is logic to your questions. The main thing to understand is that each battery is like a self contained chemical power engine. If any one cell depletes its stored electrical energy (via chemical energy) enough to trigger PCB, that results in an independent interruption of that cell's link in the circuit chain.

Electrons flow in batteries from Negative end to Positive terminal. The Voltage represents the potential difference of electron attraction between anode and cathode that was created by charging and separating chemical electrolytes "into their separate sides," where they remain, transfixed, until the "bell" sounds and the circuit is closed.

However there is no appreciable movement of the electrons without a complete circuit. Once the circuit is closed, and the load of lightbulb converts this electrical (now the electrons start moving) energy into light and heat energy, the chemical electrolytes return to their uncharged (empty) condition.

Once the individual cell has electrolyte reaction reversed ("used up"), there is less separation of charged components, and less potential electrical difference ("Voltage") remaining between the anode and cathode. 

This run time chemical electrolytic reaction is happening internally, and there is not enough voltage from adjacent (in series) cell to recharge more highly depleted cell (2.0V in your example), so its PCB trips, opens the circuit, and that shuts down current flow for all batteries. So the first protected cell to use up its chemically stored, electrical energy, and thereby have the voltage drop to PCB cutoff....breaks the circuit independently.

This may not be exactly, technically accurate from an electrical engineer's standpoint, but it is my general "batteries for us dummies" guide to explain your good question.


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## VegasF6 (May 16, 2008)

Well I have to say I have really learned from this thread, thanks for all the great answers. The cheaper cells I mentioned above, is the problem more in the battery itself, the protection circuit, or both? 

And a list of reliable cells would include, Pila, Wolf - Eyes, AW, and that's about it?


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## mikeh (May 16, 2008)

It should be added:
for a torch that takes loose li-on cells in series, protected cells are not only safe,
they are *essential*! 
But most companies would never make such a device anyway, and series li-ion cells are normally permanently soldered in a pack with controller.


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## 45/70 (May 16, 2008)

Just thought I'd throw in that voltage is measured across two points (in parallel), not necessarily a complete circuit. In the case of a protected cell having it's own protection PCB, it's measuring across itself, so no matter how many cells you have in series, it will read just it's voltage.

Dave


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## LuxLuthor (May 16, 2008)

These are general concerns, as I have not had the interest to take the cheap brands apart or rigorously test each aspect of their performance, but there have been many anecdotal failure reports of the cheaper brands, and with an explosive/fire risk of lithium cobalt, it is one of the few things (also lithium chargers are in same cateogry) in flashlights that is not worth going the cheap way.

I think there are several concerns with the other batteries besides the W-E, Pila, AW you mentioned. The biggest issue is their lack of consistent QA screening, so you have a random quality/defective incidence of problems. You may get good cells and/or good PCB....or not. 

Obviously there can be exceptionally high quality items made in China, USA, Japan, South Korea, India, etc..., so it's not a xenophobia issue, but when the focus is on "cheap," it is like comparing high quality Surefire to a light from DX, Kai, K-Mart, Ronco, or the latest "Hello folks, it's Billy Mays here" infomercial selling you a $30 supply of Mighty Putty (epoxy) to replace the handle on your $5 coffee mug.

Besides the random defects since there is little or no QA. The cheap brands start with lower quality components used in the PCB and battery construction. You should not have an expectation that the PCB protections will work reliably, or that it is adequately protected from physical damage...even though the one you got may be OK. There is not the same level of testing and performance certification/documentation, nor a primary concern for reputation. 

With the cheaper brands, the consumer is not as consistently satisfied, and has a harder time holding them accountable. Even though AW (& Pila) are selling from Hong Kong....their reputation for quality and service is something that they have cultivated and maintained for a number of years. When you get AW's batteries, C/D bulb holder/Drivers, etc., and see his level of service and personal attention, it is obvious that he is someone who provides exceptional service.



mikeh said:


> It should be added:
> for a torch that takes loose li-on cells in series, protected cells are not only safe,
> they are *essential*!
> But most companies would never make such a device anyway, and series li-ion cells are normally permanently soldered in a pack with controller.



I don't agree with either statement, since protected cells are only as safe as the components used to make them. Technically, it is also not essential to use protected cells. I used unprotected lithium cobalt cells in several lights for over a year before I found out what could go wrong if their voltages get out of balance....and most of the exploding/fire risk is from charging cells kept in series. There are still many people who use unprotected cells, but hopefully they understand their limitations, and how to use and monitor them safely. 

Lithium Cobalt Ion cells are never soldered, as that heat would be extremely dangerous. They are spot welded with thin nickel strips that are then soldered to contact points on the PCB protection circuit that controls the whole pack.


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## eyeeatingfish (Sep 8, 2008)

Im going to revive this threat because it is sort of what im confused about.

I was directed to this thread from a thread I started about using lithium ion batteries in a mag 85. The link is here
https://www.candlepowerforums.com/threads/206633



I didnt see any mention of a problem of using a larger number like 9 AA size LiIon batteries. Im not sure if i understand exactle how the juice runs throught PCB cells yet. So the voltage of one battery doesnt run through the second one, it runs past it on PCB lights and thats why the battery doesnt have too much juice flowing through it?
The thing about making sure the batteries have a similar charge I dont understand too well. It sounds as if one is a bit lower it will act as if it is being charged by the other batteries or the other batteries will want to charge it or something? Is it not the case that a flashlight will naturally draw energy out of batteries differently? When i charge my mag 85 cells i notie some of the AAs charge quickly as if they aren't all draining at the same exact rate. Cant remember if ive ever gone to measure it yet.


Imm still a little bit lost on how multiple PCB LiIon cells work and all.


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## mikeh (Sep 8, 2008)

If a Li-Ion cell is discharged too much (<~2V) it will die.
With a single cell driving an LED, you will see it dim before that happens.
With unprotected cells in series, you can easily run one cell flat, and kill it.

does that help?


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## eyeeatingfish (Sep 8, 2008)

Well, I kinda new that much already. Originnally i was wondering about running 9 AA size protected li Ion batteries in a Mag to get like 27 volts but someone said that wasnt safe.
So i was wondering about 2 or 3 PCB 18650s in series.



mikeh said:


> If a Li-Ion cell is discharged too much (<~2V) it will die.
> With a single cell driving an LED, you will see it dim before that happens.
> With unprotected cells in series, you can easily run one cell flat, and kill it.
> 
> does that help?


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## VegasF6 (Sep 8, 2008)

eyeeatingfish, I am glad you moved your questions here to get a definitive answer, since I wasn't too sure about it still. But, I will take another stab at it, someone will correct any mistakes. 

I THINK, in the case of the nimh or unprotected cells, they can get out of balance because they all share a common ground. But, with the protected cells, each protection circuit is a seperate circuit in itself, touching both the positive and negative of each battery. So, even if only 1 battery out of 3 or 9 or whatever drops to a dangerous level, it will still cut off. Even though they are in series, and the power from one cells passes through the next, it doesn't effect how the circuit works on just the one. 

At least, I hope that is correct. I do know there have been lights made with multiple 14500 protected in series, it must be considered safe. 

Her is a 4x14500 series holder that five mega made.
https://www.candlepowerforums.com/threads/195559

And there is also a 9x14500 holder, but it is 3 banks of 3 in series/parallel. 
Perhaps the only reason we haven't seen 9x14500 in series is there is no application for it yet. 4.2x9 is 37.8 volts, and you could see higher than that depending on your charger. So for the case of LED's there is no single regulator board that I know of for voltage's that high. And in the case of hot wires, it goes back to high voltage but low current like we discussed in the other thread.


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## eyeeatingfish (Sep 8, 2008)

the high voltage low current thing i dont quite get. I was just thinking a bulb running at 27-37 volts would make one heck of a flashlight. I wouldnt expect that to be used for LEDs though.


But what was the part about making sure they are charged equally? I didnt think that would be a problem and if so the PCBs would handle that.


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## mikeh (Sep 8, 2008)

VegasF6 said:


> I THINK, in the case of the nimh or unprotected cells, they can get out of balance because they all share a common ground. But, with the protected cells, each protection circuit is a seperate circuit in itself, touching both the positive and negative of each battery.



Ummm.... I this advice is way off, or at least makes no sense.
Please be careful. Li-Ion can be very dangerous if you don't understand.


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## mikeh (Sep 8, 2008)

eyeeatingfish said:


> But what was the part about making sure they are charged equally? I didnt think that would be a problem and if so the PCBs would handle that.



What are you trying to say? That the PCBs will ensure they are evenly charged? No.


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## shadowjk (Sep 8, 2008)

You need to charge them individually.


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## VegasF6 (Sep 8, 2008)

mikeh said:


> Ummm.... I this advice is way off, or at least makes no sense.
> Please be careful. Li-Ion can be very dangerous if you don't understand.


 

You are right, that didn't make any sense, although it seemed to in my head 

When Dave replied below with "Just thought I'd throw in that voltage is measured across two points (in parallel), not necessarily a complete circuit. In the case of a protected cell having it's own protection PCB, it's measuring across itself, so no matter how many cells you have in series, it will read just it's voltage." it made sense to me that because each circuit has an isolated ground, it works. As opposed to just reading pack voltage. It wouldn't be possible with a common ground I don't believe.

But, I think we are all agreeing that yes, it will be safe to run a series pack of protected li-on's be it 2 cells or 9. 

The point would be to charge them seperately, not as a pack, and I think you should check your voltages with a meter first. The PCB will stop any reverse charging if they do get out of balance, but it is good practice not to trust it more than necessary.

So yes, if you found a bulb to use that could handle the voltage, and the current draw wasn't more than 2C you will be fine. If the current draw is too high, it simply won't light. For instance, this bulb would work.
http://www.toolbarn.com/product/bosch/2610948135/

But, that probably won't be very impressive 

High voltage low current lends itself to LED's, not incan. You could run 10 or so high power leds. It would probably have to be direct drive with a resistor as I don't think any of the current drivers are designed for this voltage. Something could be designed around the LM317 regulator probably, or if not, then I am sure National would have something else.


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## eyeeatingfish (Sep 9, 2008)

mikeh said:


> What are you trying to say? That the PCBs will ensure they are evenly charged? No.


 

no, i mean why would you need to charge them individually if the PCBs would prevent any one of the batteries from falling too low.
Ive never seen a warning on any 2x18650 light about making sure both batteres are charged evenly. Like the MVP page on batteryjunction.com


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## shadowjk (Sep 9, 2008)

The PCB is the last-resort protection. You don't want to actually rely on it or use it more than necessary.

When you charge the pack, the battery that first gets overcharged will trip its protection circuit. That interrupts the charging of the entire pack, and some cells will not be fully charged.

When you then put the pack back into use, the cell that got the smallest charge will trigger its protection circuit when it gets overdischarged, interrupting the entire pack.

When you do this again and again, the most fully charged and the least charged cells will be repeatedly hammering into overcharge and overdischarge, adding wear and tear making them perform even worse, as well as limiting the total performance of the pack.


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## eyeeatingfish (Sep 9, 2008)

So if one cell has the PCB interrupt it then whole light will stop working?

How would the batter get overcharged with the PCB? Or are you saying if the PCB fails?

And if this is the case then are the side by side chargers like the ultrafire one bad then?


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## eyeeatingfish (Sep 16, 2008)

Whats the difference between current draw and voltage?

And why would the batteries need to be charged evenly? I dont have to worry about that for NIMH batteries, there are no warnings on 2x18650 lights.


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## mikeh (Sep 16, 2008)

eyeeatingfish said:


> Whats the difference between current draw and voltage?



Oh dear. What are schools doing these days? 
Perhaps you could get a thing called a "book" and learn the basics first.


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## VegasF6 (Sep 16, 2008)

The wattage, amperage, or current is what kills you 

Think of it this way, you can have a 120 volt light bulb in a 60 watt or a 100 watt. Which one pulls more current? Think of a hair dryer or a microwave at well over 1000 watts, but still the same voltage. That's current. 

So, if you have a 6 volt bulb at 35 watts, or a 18 volt bulb at only 5 watts, which would be brighter, but pull more current?

2x18650, or any 2x li-on lights often don't have warnings, but they should. Some more responsible manufacturers do mention things like at the first sign of dimming stop using. (This applies more to unprotected cells though)

All battery packs should be balanced, be they nimh, nicd, li-on whatever, but the difference is nimh doesn't explode, you just risk damaging one cell. If you have ever had a pack go bad in a tool battery, cordless phone, whatever, odds are that one cell was more damaged than the others and that is what drags everything else down. 

Since we aren't using pre built packs with balancing circuits we are responsible for that balancing ourselves. If you buy 2 new cells and always dedicate them to the same light and always charge them together, you will be fine.


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## eyeeatingfish (Sep 16, 2008)

Are li ion batteries limited at what amount of watts they can give? The bulb doesnt dictate that does it?
I understand that a higher volt bulb without the wattage. But why would a mag mod running 27-35 volt range not be possible, surely there must be some bulb that would work with that voltage and wattage, or is it a limitation of the battery?

I was trying to find a good book about electronics but havent found one yet. I read reviews about electricity for dummies and stupid etc. but they didnt get good reviews.


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## Fourinchdragslicks (Sep 20, 2008)

There is a fundamental misunderstanding of electricity here.

voltage adds
-This means that as you place cells in series, you add the voltages. think of it as stacking blocks on top of each other. The more you use, the taller it gets (more voltage) However as far as each block (cell) is concerned, it still maintains the same height (voltage) as it originally had. It does not "see" the rest of the blocks (cells).

currents passes through
-This is like joining sections of hose together and running water through it.

wattage is a combination of the two
Watts=volts*current (amps)

wattage is dependent upon resistance (incan) once the resistance has been determined, the current passing through the bulb is determined buy the voltage applied to it. 



The primary benefit of increasing voltage, is that it reduces current requirements from each battery, thereby reducing the "strain" on each individual cell, So long as bulb is being regulated. Every cell has its own characteristics, so the more cells you use, the more "unique" characteristics you throw into your pack. if one cell fails and for whatever reason its voltage drops, it increases the current demanded of each cell. In the case of protected cells, this could cause the pack to "stop working" for the reasons mentioned above.


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## mikeh (Sep 20, 2008)

Fourinchdragslicks said:


> There is a fundamental misunderstanding of electricity here.
> ...(incan) A 20watt bulb will still consume 20 watts of power independent of the voltage applied to it


So if I plug in an American 20w light bulb to my 240V socket, it will still work fine? 

Q. Whats black and hangs from the ceiling?
A. An electrician who learned his job from reading internet forums.


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## Fourinchdragslicks (Oct 25, 2008)

mikeh said:


> So if I plug in an American 20w light bulb to my 240V socket, it will still work fine?
> 
> Q. Whats black and hangs from the ceiling?
> A. An electrician who learned his job from reading internet forums.




yeah, it will work very briefly. here on cpf in the incan forums, users regularly do what you are talking about... overdrive their bulbs. go look at the wiki for your bulb life calculations. for the duration of time that you would have that 120v 20W american bulb hooked up to 240, it will draw nearly 80W.


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## mikeh (Oct 25, 2008)

Fourinchdragslicks said:


> 120v 20W american bulb hooked up to 240, it will draw roughly 20W (as it heats up, it will draw more) A light bulb is merely a resistor what happens to emit light.



Are you taking the ****? Stay in school, kid.


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## qwertyydude (Oct 25, 2008)

If you take a 20 watt US bulb, and run it on 240v you almost quadruple the power output. Power is I^2*R. Not exactly quadruple since the bulb has a positive temperature coefficient of resistance but given a fixed resistance, if you double the applied voltage you double the current. So it will burn out because you'll be running nearly 80 watts!

But protected li-ions is necessary in series. And in series they do not have a common ground. They way these pack work out is that the strong cell ends up trying to reverse charge the weak cell as the battery dies. So the weakest cell whether nimh or li-ion will die an early death if you keep taking the pack below it's rated minumum voltage. Oh yeah and you can "balance" nimh batteries, it called trickle charging charge at less than c/10 overnight and you bring all cells to max charge. 

In li-ion's case you do not want battery voltage dipping below 3 volts under load. I don't know why the protection kicks in at 2.75, that's conducive to early cell failure. I try to never take my cells to that level and I have some lithium batteries already 5 years old still running strong. They rarely get below 3.3 volts/cell and are balanced every time they're charged.


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## Fourinchdragslicks (Oct 27, 2008)

Begging pardon, correcting posts as appropriate. The last involved electronics project I had was a regulated design where my constraint was the wattage. It was (relatively) constant even as the input voltage was changed.


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## EngrPaul (Oct 27, 2008)

When I buy a light that uses 2 rechargeable lithiums, I look for one that has the appropriate shut-off at a safe voltage. That way, I can use unprotected batteries in series, which I feel is optimum.

This was a good thread until it went off on a tangent.


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## Tythagoras (Oct 28, 2008)

eyeeatingfish, (or anyone else) I have found that "Teach Yourself Electricity and Electronics" by Stan Gibilisco is an exellent book to read. It goes into some mathematics, particularly in AC circuits, but it keeps it minimally simple and explains all of the math before you get into it. It's also not very expensive, compared to other books of its quality.

http://www.amazon.com/dp/0071459332/?tag=cpf0b6-20

Forrest Mims is another good author whose books I have experience with. He explains things very simply, and illustrates clearly. I don't have any of his books handy, unfortunately.


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## lyyyghtmaster (Jan 27, 2009)

The ability to connect more and more protected cells in series is not unlimited. At some high enough pack voltage, a tripped protection circuit has the potential of being burned out due to excessive reverse voltage being applied across it by the other untripped cells. I don't know what this voltage is, or how (or if) the circuits are designed to fail in this case, but the results could conceivably be very bad indeed. 

Does anyone have more specific information regarding this failure mode?

Thanks!


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## friendly1_uk (Oct 16, 2018)

lyyyghtmaster said:


> The ability to connect more and more protected cells in series is not unlimited. At some high enough pack voltage, a tripped protection circuit has the potential of being burned out due to excessive reverse voltage being applied across it by the other untripped cells. I don't know what this voltage is, or how (or if) the circuits are designed to fail in this case, but the results could conceivably be very bad indeed.
> 
> Does anyone have more specific information regarding this failure mode?
> 
> Thanks!



I'm here looking for this very information. I have aired the fact on forums over the years, to an equally show stopping effect. 

As soon as the first protection device opens, it see's full pack voltage across it. 

Example, at 10S the disconnection device would see around 30 volts across it. Presuming the cells were around 3v each when disconnection occurred. 

I have seen people getting away with 8S packs. Having looked at cell spec lists, I have to wonder if this idea has escaped the manufacturers. 



My interest is EV's so a high cell count is normal. 


I have noticed, that generally speaking, power electronics falls within certain thresholds. Around 35v being a common maximum value for many devices. 50v less common. 100v and your list of devices is getting short. All cells are going to carry different devices, but there should be some sort of industry wide expectation, and higher voltage versions available I would of hoped. 

I'm not seeing anything still, and this is not a new thread.


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