Chargers Battery won't balance

[pvolcko]

So I've got a 6S 5000mAh Turnigy nano-tech pack. I puffed it slightly once due to over discharge (put it in the heli for a flight by accident).

Lately it has been causing my charger to not complete the charge and balance (iCharger 3010b). All other packs complete fine and in expected time. This one, though, gets up to 4.18-4.20v on each cell and it sits there balancing for ever. I actually put it through practically 6 hours of balancing after it had charged and it still would not complete the cycle. It got one cell up to 4.22v, 3 to 4.20v and two at 4.19v. The 4.22v cell is always "flashing" when I go to the cell voltage display, which I'm assuming means it is draining that cell while the others catch up.

Any ideas why this pack won't stop balancing? Doesn't seem like .02-4v variance on the cells would lead to never ending balancing. Other packs end up with a similar spread on cell voltage and they end the cycle without issue.

 

[Tony]

Actually, the flashing on the iChargers means that cell is no longer taking a charge. I would take the pack and fly the ever loving crap out of it. I'm talking, put it in the heli and beat the hell out of it in the sky. When your timer goes off, keep flying for another minute, then come in and just hover until the ESC cuts off the power. Is this good for the battery? No. But neither is a pack that is not balancing.

Once you have discharged the pack, put it on the 3010b and do a fast charge. Not a balance charge, just a straight fast charge. If this is a 2c pack, then charge it at 12 amps, just slightly above what is called for. If it's a 5c pack, then crank that sucker to 30 amps and let her rip.

Rinse & Repeat!

Keep doing this for a couple flights, then stick it on the balance charge and see what it does. If nothing else, it's an excuse to fly your heli lol.

 

[pvolcko]

I don't mind doing some fast charge cycles on it, but the flying it down to LVC doesn't seem good. It's going to puff the battery out like crazy. I started having the problem after I did that to the pack by accident and puffed it a bit. I put it on a slow balance charge since it got drawn down so much that time. I'll fly it past the timer, but not to LVC, and do the fast charge a couple times and see if it comes back into balance.

 

[Tony]

Fair enough and don't blame you there. I was just stating what I would do if it were my battery and I knew it was on it's last leg. Let us know how it turns out.

 

[RandyDSok]

What Tony said also makes sense in another way... sometimes when a pack doesn't balance out... doing several complete discharge/recharge cycles will bring it back. Using the heli ( or plane or car etc ) just makes doing it a bit more fun than doing it on the charger.

 

[murankar]

Tony's idea will prove one of two things. You will know if it's bad or good. Plus the knowledge you gain from that will help with future battery issues. Good luck and hope the pack recovers.

 

[pvolcko]

Okay, I'm starting to think this isn't a battery problem. Now all three of my 6S 5000mah packs for the 550X are doing this. The two that have recently started having the balancing issue haven't been puffed or flown down anywhere near LVC (well one was when I first got the heli months and months ago, no issues since and has been balancing fine). Almost always 1C charge rate, occasionally 2C. Packs are rated at 5C charge and don't even get warm at 2C charge.

On two packs it seems like the charger can not pull the #4 cell down to balance out. It stays at 4.2V while the others hover at 3.6-3.9. On the nano-tech pack it is a different cell that can't be drawn down, but it is a similar issue.

IR on the cells on the packs are all within 1 mOhm of each other and all read in the 3-6 region. Total pack IR is in the 25-35mOhm ballpark. Perfectly reasonable for 30-40C discharge rated packs. All probably have around 20 cycles on them each, maybe a few more.

I also bought one of those battery balancers that hook up to the balance plug and just discharge cells until they are close to each other. It takes for freaking ever (low discharge rate on a 5000mAh cell, oy) but it will pull them down to within .01V of each other. Of course it takes so long that by the time it has done it the target voltage has dropped .2V or more just from idle/parasitic discharge.

I'm calling the place I got the charger (and one of the packs) to see what they'll do for me. I'm suspecting the charger (iCharger 3010b) has failed in some way. There's no other reason for this problem to have spread to my other packs, like some kind of virus.