Blarson posted his project the BatLev, a LiFePo4 cell balancer in the project log forum:
Lithium Feric Phosphate cells are a lower engergy density variety of lithium-ion cells that don’t have the fire hazard and short life problems of the more common li-ion cells. They are popular for electric vehicles and are gradually making their way into marine and RV applications. When used in series (for higher than 3.2 volts), they need protection circiutry to avoid over-charging a cell.
This project is a cell balancer, that acts about like a zener diode. Over the set voltage, (variable over a small range) it acts as a load on the cell, turns on a red LED, and has a opto-isolated indicator for turning off the charger. The TL431A is followed by a two-transistor amplifier for the 3.3 ohm 5 watt load.
LiFePO4. Not trying to be a smartass here. If somebody buys a polonium battery and dies of leukemia, you’d never forgive yourself.