What causes a lipo battery to become unbalanced?

[Daniel Forsyth]

One of the lipo batteries on a 4S mod of mine has one cell that has a lower voltage than the others and will only charge the battery to 70% of the capacity.
Here's a pic of EScribe, cell number 2 is lower.
What is the cause of that cell being unbalanced?
I'd rather avoid any further hassles
@Mooch any lipo info would be very much appreciated Mate

 

[ShamrockPat]

Well, the inner cells usually retain more heat than the outer cells, but really LiPo's like to keep being used. The balance charger will bring cell 2 back up, but it could take a day or two to do it. It's very slow the way the balance charger works. It'll bring each singularly to 4.2, then drop it, charge the others till one or 2 is back at 4.2, all the while slowly cell 2 up bit by bit.

If you could remove the battery, you could just charge that 1 cell by hand, by plugging into cell 2 via the jst (white) connector on the battery itself.

Once it's balanced and in use, you can see if cell 2 is just weaker.

 

[Daniel Forsyth]

Well, the inner cells usually retain more heat than the outer cells, but really LiPo's like to keep being used. The balance charger will bring cell 2 back up, but it could take a day or two to do it. It's very slow the way the balance charger works. It'll bring each singularly to 4.2, then drop it, charge the others till one or 2 is back at 4.2, all the while slowly cell 2 up bit by bit.

If you could remove the battery, you could just charge that 1 cell by hand, by plugging into cell 2 via the jst (white) connector on the battery itself.

Once it's balanced and in use, you can see if cell 2 is just weaker.

Thanks for the info Mate
I bought myself a balance charger recently just for the job.
It's my big white beast that needs attention and I plan on taking the battery out to charge up on the balance charger.
Thanks again Pat and my Good Wood thanks you too

 

[Daniel Forsyth]

I received my new balance charger today @ShamrockPat and pulled the lipo battery out of the custom mod and charged it up.
I wasn't able to get the single cell out because it's a sealed lipo pack so I just gave it a balance charge and it worked a bloody treat(saves me buying a new battery!!)
100%!!!
Cheers Mate

 

[ShamrockPat]

I wasn't able to get the single cell out because it's a sealed lipo pack so I just gave it a balance charge and it worked a bloody treat(saves me buying a new battery!!)

All the LiPo I've seen are sealed. 4 individual cells, wired serially, then that protective wrap around all 4 (in your case). Your mod already has a balance charger, but even so if you re-read my post I mentoned to charge that 1 cell via the jst connector. Anyway, it's a moot point.
I'd check the voltages to make sure it's balanced, then vape on it, then check the voltages again before charging.

 

[Daniel Forsyth]

All the LiPo I've seen are sealed. 4 individual cells, wired serially, then that protective wrap around all 4 (in your case). Your mod already has a balance charger, but even so if you re-read my post I mentoned to charge that 1 cell via the jst connector. Anyway, it's a moot point.
I'd check the voltages to make sure it's balanced, then vape on it, then check the voltages again before charging.

You say my mod has been a balance charger. Where would this be situated?
I know the DNA chip has charging capabilities but not balancing. If my mod did have a balance charger it would have been restoring the battery, the voltage was getting worse over time in the mod with use!
It's all back on track now is the main thing though Mate, I'll double check the single cells on EScribe today

 

[Mooch]

One of the lipo batteries on a 4S mod of mine has one cell that has a lower voltage than the others and will only charge the battery to 70% of the capacity.

As @ShamrockPat mentioned your mod has a balance charging function. There is a chip on the board that handles that, a good one. But if your mod hadn’t been fully charged in a while then the chip couldn’t do any balancing.

If you have been using and fully charging that mod all along then I do not know why that cell was low unless it has reached the end of its life and the mod can’t keep up with the balancing it needs anymore.

 

[Daniel Forsyth]

As @ShamrockPat mentioned your mod has a balance charging function. There is a chip on the board that handles that, a good one. But if your mod hadn’t been fully charged in a while then the chip couldn’t do any balancing.

If you have been using and fully charging that mod all along then I do not know why that cell was low unless it has reached the end of its life and the mod can’t keep up with the balancing it needs anymore.

Thanks Mooch
I'd always charge the mod up to maximum percentage which was 100% for quite some time then suddenly it dropped and wouldn't charge any more than 73%.
I do always keep on top of the charging of my lipo mods but I am only a light vaper and I have 6 custom mods so they don't get as much use as they probably should.
I have put the low charging bat. on a balance charger and it has brought it back up to 100%.

Do you think this will fix the lipo battery back up again and keep?
Or will a new battery need to be gotten?(I hope not)

 

[dwcraig1]

I had a situation with a 3 cell DNA200 like that so I put in a new battery. Then the problem came right back as soon as I let the mod sit unused for awhile. It turned out to be juice on the board underneath the JST connector causing the one cell to slowly drain. I cleaned it without removing the connector from the board by squirting Kester 951 no clean liquid flux under it. I still have the mod now and the cells stay balanced.....and I pretty much never use it.

 

[Daniel Forsyth]

I had a situation with a 3 cell DNA200 like that so I put in a new battery. Then the problem came right back as soon as I let the mod sit unused for awhile. It turned out to be juice on the board underneath the JST connector causing the one cell to slowly drain. I cleaned it without removing the connector from the board by squirting Kester 951 no clean liquid flux under it. I still have the mod now and the cells stay balanced.....and I pretty much never use it.

Good to hear you got it fixed up Mate
I definitely don't have an issue with leaking juice

 

[dwcraig1]

Nov. 09, 2015 right before the time I changed the LiPo. It's still good.

 

[Daniel Forsyth]

Nov. 09, 2015 right before the time I changed the LiPo. It's still good.

That's nice but it doesn't affect me at all mate

 

[Mooch]

Do you think this will fix the lipo battery back up again and keep?
Or will a new battery need to be gotten?(I hope not)

Sorry, there’s just no way for me to know. The only thing you can do is keep a close eye on the voltages and see if the pack behaves or whether you will need to replace it.

 

[Daniel Forsyth]

Sorry, there’s just no way for me to know. The only thing you can do is keep a close eye on the voltages and see if the pack behaves or whether you will need to replace it.

I thought that might be the case. I've been doing just that and everything seems to be fine so far with a regular check on EScribe, I'll make sure I keep on top of this one!

Thanks for your help with my problem Mate

 

[ShamrockPat]

Daniel Forsyth in escribe ... mod ... battery section, you have the option when charging to maximize charges or puffs. If you were to choose 'charges', it would only charge to 4.1v instead of 4.2v. They claim that will extend your battery life.

IMHO, if you know you're not gonna use one for a long time, you could vape them down to their shipping voltage, or even (theoretically) change the battery type to LiFePO4, which would then only recharge them to 3.6v. Batteries just hate sitting there unused and fully charged.

 

[Daniel Forsyth]

in escribe ... mod ... battery section, you have the option when charging to maximize charges or puffs. If you were to choose 'charges', it would only charge to 4.1v instead of 4.2v. They claim that will extend your battery life.

That's handy to know Pat, Thanks Mate
I'll jump on EScribe soon and have a bit of a look!

All of my lipo mods get a good constant rotation so they never sit there unused