One of the major issues with electric vehicles is keeping the battery pack healthy so it lasts a long time. The issue with having a long string of batteries is that when you charge them, not all batteries charge at the same rate. Without going in with your multi-meter and measuring the voltage on all the batteries individually, it's hard to keep track of which ones aren't as charged as the others. The Zivan NG3 charger I have does an equalization charge after its main charge to try and bring the lower voltage cells up to their full level. The downside of this is that the cells that are already charged tend to boil and lose water.
I spent today doing research on battery management systems. I'm developing a charge equalization circuit that should help greatly with the unequal charging that happens with a long string of EV batteries. There's also the problem of sulfation which requires a pulsed desulfator to clean the battery plates after awhile. Here's some links for charge equalization and desulfation:
Charge Equalization: (click on Technical Whitepapers)
I'll post the schematic and board layout for the charge equalization circuit I'm working on soon.