Bad cell ?

[camobob]

I just got a few 4s packs and I threw them on my balance charger and a couple of them have 3 cells at 4.20 and one cell at 4.5 and another pack a 4.8. Is this acceptable ? I cant seem to get it to balance out.I even tried charging at .5c to seep some power in it but she wont take. Should I try a higher charge rate of 1.5 or 2 c ?

[heyok]

Originally Posted by camobob

I just got a few 4s packs and I threw them on my balance charger and a couple of them have 3 cells at 4.20 and one cell at 4.5 and another pack a 4.8. Is this acceptable ? I cant seem to get it to balance out.I even tried charging at .5c to seep some power in it but she wont take. Should I try a higher charge rate of 1.5 or 2 c ?

As I understand things, a full charge on a Lipo is about 4.2 volts per cell. Adding more charge to balance your pack isn't the way to go here. You need to discharge the pack (ideally just the cells that are higher than 4.2 volts, but this is difficult to do).

I suggest you use the packs to bring them down a bit. Probably don't go real hard, but use them so maybe 30% of the charge is used then put them back on your balance charger. If you have something like a Blinky Balancer, that would work too.

[Chevdog]

I agree with heyok, either use the battery or try to discharge it and then balace charge it again. It may take a few cycles to get them all perfectly balanced out again. With lipos, you don't want to go over 4.2 volts or under 3 volts per cell. So if 3 are currently 4.2 and one is 4.5, if you try to add voltage and balance, all you are going to to is continue to hurt the battery. If you charger has a discharge feature, try to discharge it to anything above 3 volts per cell, then do a balance charge to even out the cells. I know with my electrifly charger, if I just plug in the balancer, it will slowly balance the battery with out adding any voltage.

[camobob]

Sorry thats 4.05 per cell not 4.5 I had to reread to figure out what you guys were talking about. So my cells read out like this 4.20 4.05 4.20 , and my other pack is 4.20 4.20 4.03

[heyok]

Well, that sounds more typical!

I think my advice will stay the same. Maybe partially drain them and then charge them up with your balance charger, or let them sit on the Blinky Balancer or whatever you have (for a long time) until it is done.

That is an imbalance, but I don't think I would be too worried about it. I think it should come back.

[Hvrc]

From my 3s zippys, when I charge at 1c or .5c, they tend to do that, but if I charge at 2c (max rating) they balance out perfectly. Weird I know, but it's true. As they stated above, 30% down and recharge. They may be cells on their way out (hate to be the bearer of bad news) but after cycling a few times and they still end up like that, they won't charge soon after at all.

May have to consider a little cut and solder soon.....

[cchriste]

Some of my HK packs need to be balanced before AND during charging. I use a Blinky for about 30 min before the charge, then during the charge, and sometimes about 5-10 minutes after the charge. But...some of my other HK packs are perfect and hardly need balanced at all. They should get better though after a few cycles.