2 x 7.4 LiPo - different charge values!

[ScutuMix]

I have two identical batteries and they are end charge at different values. How can I fix this and what is wrong with them?

2x Batteries: http://traxxas.com/gallery/batteries...mah-74v-2S-25C

Charger: http://traxxas.com/products/parts/ch...hargerplus6amp


Thanks!

[kwitty]

Can you give the details of your results, has each batter been cycled about the same amount of times, of the same age?

Do you 'balance charge' each time or fast charge or????

[ScutuMix]

Balance charge - both same age - 1 month, time of charge, about 80 min!
I use them both for my summit 1/10.

[ScutuMix]

This is the final screen when the batteries are fully charged!



http://imageshack.us/photo/my-images/707/photoydj.jpg

[trax de max]

charge the packs on there own. see if the cells get closer together

[ScutuMix]

Thanks, I'll try that!

[ScutuMix]

yes, they are go up to 4.20, but when they are both connected one is going to 4.20 faster, the other one steel need 15 min or more.

charge the packs on there own. see if the cells get closer together

I'm using this with them:

http://traxxas.com/gallery/Accessori...LiPO-Batteries

[trax de max]

Cool. More cells that is charging will take longer at constant voltage state as it's trying to balance more cells and using maybe only upto 350 mA to do this. With one pack it's normally pretty close to start with. With 2 packs it can be quite different as one could drain faster than the other. So a single 4s would take the theoretical 60min but 2x2s would take over 70min in the same situation.
Adding another 15min at end of charge isn't that bad for 2packs.

[ScutuMix]

As I know I should not let them go more than 4.20, but when one is at 4.20 and the other one at 4.05, in 15 min more the one that is 4.20 it will go over until the other one will reach 4.20.

I don't wanna overcharge them or do something bad.

It's ok if I'll connect the one with 4.05 in a single mode after to reach 4.20 ?

[trax de max]

I've never heard of single mode charging, but your batteries are way out of sync.
You could try a storage charge. This will take a long time, As i think the max setting is 1 or 2A.
Then when it has hit storage level, check the cell voltage. If it's the same or 0.1 difference try a full balance charge again. Check voltage throughout the charge. If one cell goes to 4.21 press stop. disconnect and give a few minutes to cool, Then put back on storage mode. Give it a day then try a balance charge again.
Just remember to keep checking the voltage of the cells.
The only two options that you need on the charger is balance charge and storage. All the rest are just handy for some things.