Safe to run Li-Ions in parallel?

milkyspit

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I'm designing a parallel battery adapter for CR123A cells. It will place two stacks of 3 cells in parallel, or in other words, 2x3x123.

Pila 150S rechargeable Li-Ion cells will also fit my adapter in a 2x2 arrangement. According to manufacturer claims, these cells include protective circuitry to prevent overcharge and overdischarge. But will running two stacks of Li-Ion cells in parallel present any particular dangers, and if so, how can it be done safely? I'd like to get this right without blowing up my house! /ubbthreads/images/graemlins/ooo.gif
 

CM

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I think certain camcorder packs are wired in parallel (discharge only?) so my guess is that it's safe. If you have any weak cells during discharge, the others would just have to "work" harder. However, it's probably not good to charge them in parallel. Since you have pilas, you're probably ok since you must charge those individually.

CM
 

Doug S

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Yes, safe to do. The only precaution that you should take is to not assemble your pack with two cells of vastly different states of charge.
 

snakebite

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many notebook packs have 2 3 or even 4 li-ion cells strapped in paralell.and they dont have any special stuff in the cell either
 

Burnt_Retinas

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Milky,

Just the question I was thinking of asking. I'll see if I can get an answer from the battery pack manufacturer I got my Li-Ions from re what is deemed an acceptable risk in commercial applications. I suspect it is OK, but I myself want more info as it seems you do too.

Chris
 

Sproing

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If it is ok to do this, maybe someone should try making a Surefire M6 rechargeable pack using 2x2 Li-ions serial/parallel. Not sure if it will fit or not though..

A rechargeable M6 would be sweeeeet /ubbthreads/images/graemlins/grin.gif
 

milkyspit

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Sproing, it should fit using the Pila 150S cells. Two of those cells are designed to be dimensionally equivalent to three 123 batteries.

Burnt, for now I'm going with the advice of Doug S, and will only use the cells when they've all been freshly charged, then run them until spent. But by all means, look into matters further! Let me know what you learn. /ubbthreads/images/graemlins/smile.gif
 

CM

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I thought the M6 was configured as two cells end to end x3. The pila's voltage would not be correct in that case. Inquiring minds want to know; if the M6 can use rechargeables, then i want, no, I NEED one!

CM
 

milkyspit

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CM, I'm not the guy to answer things about the M6; don't even have one. /ubbthreads/images/graemlins/frown.gif I was just talking about the physical dimensions of the cells, didn't think about the voltage and such...
/ubbthreads/images/graemlins/icon3.gif
 

UK Owl

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Bear in mind the words of the character 'Arthur Dent' in Douglas Adams's 'The Hitchhikers Guide To The Galaxy'....

'Ah, this is obviously some strange usage of the word 'safe' that I wasn't previously aware of.'
 

Ray_of_Light

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Battery packs of Li-ions, like those of camcorders or laptops, have a single controller for charge control and low-voltage cutoff.

Hence, you can discharge Pila Li-ions in series, but you cannot charge them in series. As soon the most charged opens its circuit, the remaining one will not be charging anymore.

Parallel configuration of Pila Li-Ions gives no problem either in charging or discharging.

Series/parallel of 123 is safe if you replace all batteries at same time, using same brand and age. Also, make sure that ALL batteries makes good contact inside the battery holder.

Anthony

EDIT: I think it is possible to run the M6 on Pila Li-Ion, by using a 3.7 Volt lamp assembly. To make the 250 lumens of M6 LOLA, it should draw at least 5 Amps...
 

Hemingray

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I've had good results with up to 5 LiIon cells paralleled, I tried
9 17670 cells in parallel, and it slowly self-discharges, this was originally three separate groups each of three in parallel, they were OK, but when I tried all 9, it slowly discharges, down to about 3.8VDC from 4.1 VDC. so far, (about 2 months) it seems to hold 3.8VDC OK, so this may not be a real problem. It still works fine with NSPW500BS LEDS as is.

These are all cells salvaged from salvaged notebook battery packs.

/ed B in NH
 

Doug S

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[ QUOTE ]
Hemingray said:
I've had good results with up to 5 LiIon cells paralleled, I tried
9 17670 cells in parallel, and it slowly self-discharges, this was originally three separate groups each of three in parallel, they were OK, but when I tried all 9, it slowly discharges, down to about 3.8VDC from 4.1 VDC. so far, (about 2 months) it seems to hold 3.8VDC OK, so this may not be a real problem. It still works fine with NSPW500BS LEDS as is.

These are all cells salvaged from salvaged notebook battery packs.

/ed B in NH

[/ QUOTE ]
Ed-
It sounds like in your case of 9 cells in parallel, one of the groups of 3 must have one or more marginal cells. If all were good, 9 should do just as well as 5 in parallel.
 
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