My S-10 EV conversion has a battery pack made up of Nissan Leaf modules. I am using a mini-bms system which has a per-cell alarm, but does not report per-cell voltages and also does not do a great job keeping the cells balanced. To check individual cell voltages, or manually balance cells, I need to pull a few pins and lift up the tilt bed on the back of the truck. But it is possible to determine when cells in the battery are no longer well balanced based upon the power draw when the ending voltage is reached. You can see this most easily by looking at the charge profile graphs (provided by my JuiceBox EVSE).
When the cells are not balanced, some cells are at a lower SOC than others when the ending voltage is reached, which results in the entire pack drawing more power (in this case, charging ended when the max voltage cutoff was reached, but the pack was still drawing 3,000 watts.
After balancing the cells, the normal charging profile looks like this:
As you can see, the amp/power draw slowly tapers off as the max voltage is approached, and the pack is drawing less than 1,000 watts when the cells are balanced.
I use these end-of-charge graphs to determine when it is time to pop the back of the truck and manually check/balance individual cells. [I still have the mini-bms units to automatically stop the charger if any cells voltage goes too high, or alarm if any cells voltage goes too low.]
