I have a similar question, my tool has 4x terminals, 2 are negative & positive, the other 2 appear to be sensor wires (yellow/brown) they go into the board (resin moulded) and back to the switch that powers the tool, what is sent from the battery via these two wires and how? I plan to run Lithium Polymer batteries (with built in protection) so need to supply the correct votlage/current to these wires so the tool will operate