I don't know the resistance, just used a strand from a cable, its 0.4mm dia copper wire maybe 25cm long. Totally ignored whether the battery likes this or not! I'm not much into electrics and wires, just basic knowledge, so I'll ask my brother if he can rig something, maybe a power supply? Seen him using one to operate the robot motors etc, adjusting voltage and current and so on - so I'll ask him before I fry his battery!