How can I safely discharge a large lead-acid battery, like a car battery or UPS battery?
I assume I use a thick copper cord (I have that in the form of washing machine electrical supply lines, about a 1/4" thick) and then put a resistor in line. The problems I see with this approach:
How do I size the resistor so I am assured I am not discharging too fast and risking an explosion?
My experience is that large resistors are sick-o expensive. How can I get an appropriate resistor without spending a lot of money? Can I use graphite rod? (I can potentially get those cheaply) If so, how do I size the rod correctly?
How do I know when the battery is fully 100% discharged and completely safe?