Powering a drill motor/battery

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?)

Thinking folks will need to see some good pics to know with any certainty how to help you.

It would help if you clarify what you are trying to do. Apparently something "works fine" but it isn't clear what, nor is it clear what it is doing that is "fine". Is the Arduino controlling the drill motor? What is mcu? In one context it appears to be Micro-Controller Unit referring to the Arduino but later on it appears that the mcu is not the Arduino - maybe Motor Control Unit?

Pete

Yes, the arduino is controlling the motor which will be attached to a wheel, and MCU is Motor Control Unit.
I didn’t really go into the details, as the set up is doing what I need it to do. My only real problem is how to charge the battery now that it’s all together.

Sorry, I've just reread my original post - it should be: "drill motor and battery, to the mcu and arduino"