LiPo Cells Unbalanced

[domp444]

I have a Turnigy 5000mah 2s 40-50c LiPo, and after thinking it was broken I decided to re-examine it. I now see that my iCharger 206b is telling me that one cell is being charged up to 4.20, while the other stays at 3.84. I then tried to bring the battery into storage mode, which should bring the cells to 3.85, but that only brought down one cell and the other unequally to a certain storage voltage. It did not equal out the cells for some reason.

Does anyone have any ideas on what to do? Or is the battery done with?

[m4a1usr]

Any chance you are part of a club where other members will have a different charger? The fact that your charger took one cell up to 4.2 volts but not the other could be due to one of several reasons. It might be the balance connector but then it should have not charged the pack at all if it didnt connect well.

A lipo pack is charged thru the main leads. Not the balance leads. The balancer only works to bring down the cell or cells that are charging a bit faster then the others. What seems to have happened is your charger did not cap or limit the charging of one cell in your pack. Thats why I ask if you have access to another charger. It still could be the pack. But it very well could be your charger.

Dont junk the pack. There still could be hope. And I would keep an eye on your charger. Maybe its acting up. Maybe its not. But it should not have charged the pack with unbalanced cells.

John

[domp444]

I tried charging other LiPo's and they charged fine, as they have in the past. Therefore I do not think it is a problem with the charger. I tried charging this battery on Friday, and got a "Low Cell Voltage" warning and it would not charge or discharge the battery anymore. I put the pack to the side and didn't touch it 'till I had an idea today. I thought that maybe I could bring it into storage mode, but that didn't work and they're still unequal. Just now I don't get the warning anymore. I just tried balance charging the pack again, and one cell goes up to 4.20 while the other goes to 3.84. I am now discharging the pack to 3.80 per cell to see if that helps.

I am not part of a club, as I don't know of any in the NYC area. If you know of one please let me know!

[BakedMopar]

IMO Its the pack and not the charger. I have this problem with some of my Turnigy's, its just a bad (lazy) cell. If you can just let you balancer, balance it without charging or discharging. Then charge it up.

[hyrulejedi86]

A couple things to try:
1) Check out the local hobby shop and see if one nearby has a charger that would be willing to try it for you.

2) find a way to discharge it a little more, and then balence. Then repeat the procedure. I had one that was off. Not that far off but off after a normal run. I had to charger and discharge for several cycles to get it back in line. It now works just fine.

Its a long shot but it might work, I'm sure others might say it's done but I figure it's worth a try as long as you keep an eye on it while doing so.

[domp444]

I discharged the cells to 3.70, but they were still off. At first they were off by .35 but after discharging they were off by .20. I thought I was making progress, but after trying to charge them now, they are once again off my .35. It seems that one cell will not go past 3.85. I don't know what else to do. I will try discharging each cell to 3.4 later and then try charging them up again. Hopefully something will work!

[blackcat26]

One thing I have found is the lower amp and slower balance works good for ones that are uneven. I have had a few unbalanced batts then I used my charger to balance on 1a. Takes forever but has always worked for me. After they get balanced out it seems like they get their memory back and work just fine.

[domp444]

So I should balance charge the LiPo at 1a?
I just tried discharging it but they are still .18 apart.

[blackcat26]

Yes balance it at 1a. Gonna take several hours. May have to unplug at bedtime and do some more tomorrow. Takes awhile, but try it.

[domp444]

Yeah I started but after seeing it would take a while, I decided I will do it tomorrow. I noticed that the cells did begin to drift apart again, but I'll try tomorrow. I hope something works, otherwise I'll just toss it, won't bother with it too much.

[785boats]

A silly question perhaps, but what mode do you set the charger on when charging? Is it BALANCE mode?
The internal balancer is only activated in the BALANCE mode.
It does not operate in the CHARGE, STORAGE or FAST mode.
Just a thought.
Paul.

[domp444]

Great question actually! But yes, I am charging on Balance Mode. I think it is just a bad battery, but I will try some more tomorrow.

[JMSCARD]

I am having the same problem with some 30c 5000mah Poly Rc's.... the same ones that are now rated at 35c...per pat at rc lipos as I was buying for to match the bunch I got in the spring and he said the new ones are the old 30c batts with a 35c label.... and that the old ones were underrated..... anyhow I have wayyyy to many lipos and now I have a lazy cell on two 6s 5000 mah packs.. problem is I just don't run them enough to get them back into it.... I have tried discharging them on the charger then recharging (balance type).... but to no avail yet....

[785boats]

Well I think all possibilities have been ruled out except for it being a bad cell, after re-reading through this thread.
I had one in a 5800mah 4s pack that wouldn't charge up over 3.85V. I ended up disconnecting it, reshuffling the balance wires in the balance plug & turned it into a 3s pack that I now just run in my scale boats.
I even tried charging it in CHARGE mode so the balancer wouldn't interfere with it but that didn't help either. The over voltage protection still held the good cell at 4.2V but the bad cell still wouldn't come up.
I have read about people making an adaptor & just charging the one cell to see if it comes good. But you must get the right pins & polarity in the plug, on both battery & charger.
Might be best to just toss it & get another pack.
All the best.
Paul.

[m4a1usr]

I have read about people making an adaptor & just charging the one cell to see if it comes good. But you must get the right pins & polarity in the plug, on both battery & charger.

Thats not a bad idea if his charger will do one cell. But he will need to charge that cell at a very low rate. As the charging would be done thru the balance tap lead and they are only 22ga wire. Still if it were me I would give it a shot. Cant hurt anything either as long as he limits the current.

The way to do this is determine the bad cell, use either power lead (could be either the big red or black wire) and that will tell you what the polarity of the smaller balance tap lead will be. Charge at 250 mAh, no more then 300 mAh. See if the cell comes up. If it does come up, let it sit for a day or 2 and see how far down it drops. Then compare it to the other cell. They should be within a tenth of a volt. If you have a discharge mode on your charger try it out. See where that takes the pack.

Lipo packs need to be cycled a few times to get them operating at peak performance.

John