I would think a locksmith could make a key for you in short order, then you could see how the batteries are wired.
My 36 volt NiMH charger had 3 wires. One was for a thermistor in the battery pack.
It would be good to have a voltmeter on the batteries to monitor voltage as you charge, as it sounds like they may be in bad shape and the voltage spikes on charging till whatever watches them goes into alert mode.
Good shopping, wish I could pick up one of those for $20.
Last edited by wernmax; 06-09-09 at 10:09 PM.