man putting terminals onto a car battery

How to safely use jumper cables on your car’s battery

Whether or not you believe that the humble jumper cable was, in fact, invented by a chap named Leon Jumper, the idea of using a secondary energy source to deliver a timely “boost” of performance to a depleted battery unit has been around since the turn of the century; and applied to various forms of transportation.

While it’s always a good idea to have the working condition of your car’s battery inspected via an approved battery fitment centre before any road trip, any number of unforeseen factors can play a role in depleting this item’s energy reserves to a point where it is no longer able to perform its primary task of firing an engine to life. These include forgetting to turn your car’s lights off, operating a climate control system while the engine is not running, or even a faulty alarm system’s wiring.


If you’re unable to call upon the assistance of a trained professional or break-down service like our Battery on Call service, the presence of a second car is required to make optimal use of jumper cables. Together with the reassurance that instructions are also listed within your car’s owner’s manual, here’s what to do next:


  • Align the cars
    Confirming the fitted position of the battery within both your car and the donor vehicle, manoeuvre the latter so that the jumper cables can reach between the two batteries. Leave enough room for you to safely work between the two cars and remember to remove the ignition keys and ably the handbrake on both vehicles before beginning the jumping process.
  • Safety first
    It’s recommended to use gloves while working with a car’s battery.Inspect the general condition of each battery, yours and the one installed within the donor vehicle, to ensure that all terminals are clean and free of any debris or a white, crystal-like substance.
  • Working with jumper cables
    A modern set of jumper cables is made up of two well-insulated wires finished with two sets of so-called alligator clamps. Universally colour-coded to indicate polarity (positive and negative), it’s important to know your red cable from your black cable before beginning the jump-starting processWith the ignition on both vehicles switched off, lift any plastic protective covering away from all terminals – ensuring from this point on that no two alligator clamps touch either one another or another metal surface – securely fasten the first red clamp onto the positive terminal of the depleted battery (marked + and usually indicated by red). Once this is done, clamp the other end of the red cable to the positive terminal of the donor battery.Working slowly and accurately, now clamp the black cable to the negative terminal of the donor battery (opposite to what we did with the red cable).Now attach the only remaining unsecured (black) clamp to a section of unpainted metal within the engine bay of the vehicle that’s in need of a jump start. A common misconception is that you need to mate the two negative terminals of each battery, but this can, in turn, cause damage.
  • Ignition time
    Once the cables are secured and all persons are standing clear of each engine bay, fire the donor car’s engine to life and leave it at idle for at least three minutes. This action should allow enough charge to be delivered to the depleted battery for it to once again provide sufficient energy to start its engine. Leave both engines running for a few minutes.
  • Disconnecting
    With both cars switched off once more, disconnect the cables in the opposite order from the way they were attached. That said, first remove the black cable from the bodywork of the car before unclamping its opposite end from the negative (black) terminal of the donor car. After which it’s time to remove the red clamps, first from the donor car.


Make sure before the donor car leaves that your vehicle can fire to life unaided. With its engine running, the battery will be able to recharge to its optimal working condition once more. That said, a second successive dip in the performance of your car’s battery could indicate that it’s time for a visit to an accredited Willard battery fitment centre.