How to Wire DC Devices With Two Wires: Red and Black

Disconnect any power source from the device or circuit to which the device will be connected. Wait at least five minutes after you disconnect the power source before touching any of the electrical components to allow capacitors time to discharge. Capacitors are circuit components that store energy for a short time.

Connect the red wire to the positive terminal on the device. If your wire isn't equipped with a terminal interface -- a flat metal piece that can be screwed in place -- you will need to strip off the end of the wire. Strip off enough wire to wrap around the terminal post, but not so much that the wire might touch another part of the device. Typically this will be about 1/4 inch for most small, home devices. Loosen the screw on the positive terminal and loop the bare wire around the base of the screw so the wire makes a hook shape. Tighten the screw until it's snug, but not over-tight. Connect the black wire to the negative terminal on the device.

Connect the red wire to the positive terminal of the power source. Typically this will be a battery, but it could be the wiring coming from a battery or DC generator. If you're working with anything the size of a car battery or larger, use rubber gloves to insulate yourself against electric shock.

Connect the black wire to the negative terminal of the power source. If the battery is live and there's no switch on the device, then the device should start. If it doesn't start, check your connections and the charge on your battery and try again.