Very nice find. Thanks for reporting it.
That appears to be a buck driver. The buck converter (towards the center of the pcb) can take 4S cells. Not sure about the rest of the components though. It will probably not give much current with just 1 cell. The R150 is your voltage sense resistor for controlling current. The 6 pin component at bay U1 should be your modes chip.
EDIT: I have heard that those FET's (marked A09T) are rated for 5.8 amps. There are 2, but they don't appear to be parallel. So I don't think max amps can be doubled. Not sure what the FET with the Drain tab going to Ground is doing. I think the freewheeling diode (marked S34) is good for 3 amps or so.