I am trying to build a charger for the Ctr 003 battery for the Nintendo DS. This battery has 3 outputs, which I call +, 0, and - for simplicity. When I measure voltage from + to -, or from + to 0, I get the same reading of 2.54V. However, when I apply arbitrarily small current from + to -, the voltage jumps arbitrarily high, and then trickles back down to 2.54.
I've had this happen in protected laptop batteries. The protection circuit kept the batteries from charging, unless it thought they were inside a laptop. This problem could be overcome by running an appropriate resistor between two non + or - ends of the battery. However, in this case, there is only one end that's not + or -. What other means do there exist, to fool the protection circuitry into thinking that the battery is inside a Nintendo DS?
I'm not expecting a full answer; it would be great even just to get some ideas of what I could try with other three-output protected batteries.