eizo

Try this particular discharger circuit. I soldered it with a variable resistor, and marked it for 4 cells and 6 cells. It works well. Make sure you check your calibration with a multi-meter on each cell.

I didn't install any fan and I used a LED in serial with a 100ohm resistor instead of the bulb. You can simplify the resistor circuit if you can do your own calculations.