Apologies if this is a stupid question, but it's my first project so I'm still learning on the fly.
I've hooked up a 3.6v drill motor and battery to the mcu/arduino, which works fine, but I've accidentally cut out one important part - the recharge port.
It's a USB charged drill, with two options. One is to plug directly into the drill, the other is a usb charging station.
Inside the drill itself, the motor was wired to a board with the controller button, then a second board is connected by three black wires (not sure what they each are) which has the usb port, and a controller for a torch light. There are also two wires, black and red, leading to a black bit of plastic with metal around it (I think this is where the charging station connects into the base).
Inside the charging station, there is a single board, with the usb port, two metal prongs bent into a L-shape, and wiring leading off to a set of LED charging lights.
I've currently got:
motor to mcu (out 1,2), mcu to arduino (2,3,9), and arduino to battery (gnd vin).
Which option should I try and incorporate? And where exactly do I connect it in? Between the battery and the arduino? Or do I feed it directly into the board somehow?
(Should this go on the General Electronics board?)

