Left the lights or the car radio on? Or the car simply will not start after an extended period out of use? There are all sorts of reasons for a flat car battery, but the result is always a nuisance. If you do not have charger to hand, the jump start cable enables you to connect one car to another and supply the power needed to start up the engine. To do so, the positive poles of the helper's and receiver's battery have to be connected together, then the negative pole of the helper's battery with a ground point on the vehicle that refuses to start. Then you can get going. A jump start cable should therefore be part of the basic equipment of every vehicle.