Lipo problems

[Speedtospare]

Greetings all. I don post much but i have learned a great deal from this site. Thanks to the people who keep it running.

I have recently build a few pocket bikes for my two fantasic boys. The oldest we just converted to 44.4 V of turnigy lipo power. I am running thre 4 cell packs and another three 4 cell bats in parallel. I have the 48v 100a kelly controller set to cut power at 38V. The motor is a brushed dc chinese 750 watt my1020 style lf motor.

The pack is charged in parallel and checked after every ride. Last night i rkde until the pack hit cutoff. When i checked the individual cell voltage one cell had dropped below 3v. It seems to be dropping the 4 cell in every pack to low level. I just orded a attery medic to monitor the cell.

I dont have any visual or logging software but i wanted to hear everyone opinion.

Here's my oldest.

http://gtamc.com/album.php?albumid=294&attachmentid=5785

 

[dogman dan]

Well, you can get a lot more unbalanced by doing a deep discharge or few.

Hopefully not too damaged. Balance charge them, and see if they stay balanced overnight. If not, oh well the leaky cells are going bad. I'd say the best bet is to monitor your pack voltage better, and aim to stop sooner.

For 12s lipo, setting your lvc at 42v would be better. Likely to give you a resting voltage at lvc of 44v.

 

[shock]

38v is too low of a cutoff IMO. There is very little energy left after going below nominal. Dogman is right 42 or even 43 volts would make a better cutoff and keep your LiPo's happy and healthy.

 

[Speedtospare]

Thanks guys! I individually recharged each 4 cell and balanced them all. They all charged up with no issues are the cells are balanced again. I left them to sit overnight and I will check them again in the morning. I will reprogram the controller to 42 volts tomorrow. Im going to make a second 10 a/h pack to boost run time. This was the forest time the batteries were run down enough to activate the cutoff.