How do you charge a motorcycle battery with a car battery?

You must get a couple of so-called jumper cables. The cables have strong clamps on them and are designed to be clamped to the battery terminals. Attach the black cable to the negative terminals of the motorcycle and car battery first. Then attach the red or positive cable to the positive terminals of the motorcycle and the car battery. In case your motorcycle battery is empty, you can now start the bike from the car battery. Disconnect the cables in reverse order, beginning with the red cable. The motorcycle battery will not be charged much by the car battery but the bike can be jump started by using this method.