Lipo balancing problem
 

Ok I went to the track today to practice with a charged 4s lipo. When I charged the battery I noticed all 4 cells were good. Then during practice the buggy quit now 1 cell is 4.75 volts and the other are around 3.75. Can anyone help?

How do you balance your cells? If you have an external balancer, most of them will do a discharge balance which is it will discharge high cells to meet the value of the lowest cell. Another option would be if your charger has a built-in balancer and a discharge function, you could try using a "storage" mode on the charger or set a discharge cycle to a cell value of say 3.5V/cell.

The best chargers balance the packs in parallel while charging. They discharge high cells while the charger is charging simultanesouly. This way no one gets left behind. Ideally charging the cells individually would be the best way to go, but would take forever becuase of the small balance lead (they only handle 1 or 2 amps).
You have a problem I had with a new pack I bought from overseas recently. Discharge balancing will probaly not work, the low cell needs to be brought up to the voltage of the other 3 cells. I tried to discharge balance the low cell, but that did not work, the cell was too low so the balancer would shut off before all 4 cells matched. Cutoff voltage is not programable , probably a safety feature which is why...I rigged up a single cell charger to bring the low cell up, a better way to go, but you better know what you are doing. Youv'e been warned. :nod:
It took a few cycles of charging the cell individually then balancing before the pack was matched well. :blush:

This is why LiPos need to be balanced :p

If it's a new battery, then the issue will probably work itself out relatively quickly. Sometimes new LiPos will balance up fine, and as they discharge the cells will "drift." Every time you balance charge it, the cell voltages will likely become less and less different.

However, if it is an used pack and this problem just started, there may be a problem within the pack.

I suspect the comment “When I charged the battery I noticed all 4 cells were good.” suggests it was balance charged, is this correct?

Is the 4.75 Volts for the odd cell a typo, did you mean a lower voltage?

Only time I've seen a lipo cell read that high, it was getting ready to fail. I hope the 4.75v was a typo.


Balance chargin at low rate will usually resolve balance issues if they are not due to damage, age or a cell thats going bad.

Thanks everyone for the info.