I recently observed two people jump-starting a vehicle with a flat battery and noticed a few mistakes. When I offered to help they noted that they had it under control and eventually started the vehicle. You can jump-start a vehicle using a charged battery from another vehicle, a charged battery or a battery pack. If you have roadside assistance use it, let a professional restart your car.
Otherwise, if you have to then there are a few steps that you should follow to do it correctly. Firstly check your owner manual to see if the manufacturer has specific recommendations regarding jump-starting.
Careless use of jumper cables can have serious consequences given the level of technology in modern vehicles. Back in the day engine management systems were simple if even fitted. Today incorrect use of jumper cables can damage the ECU ( Computer ) which could mean a costly repair.
Position the two vehicles facing each other so that the jumper leads will be able to reach both batteries. The flat battery and that of the working car. Both cars should be in neutral with handbrakes engaged. In the case of an automatic vehicle, it should be in park mode ( P ).
Open the bonnets of each vehicle and locate the batteries and ensure that the terminals are accessible. Some may have plastic caps which you will need to remove.
Lay the jumper cables out to ensure that they are not tangled and check that the clamps are not damaged.
The battery terminals will be marked as negative ( – Black ) and positive ( + Red ). Your jumper cables are in two colours. The red cable will be for the positive terminal and the black cable will be for the negative terminal.
Firstly connect the red cable to the positive terminal of the flat battery, then connect the other end to the positive terminal of the vehicle with the charged battery. Under no circumstance should the clamps touch each other as this can cause damage to either vehicle. Then connect the black cable to the negative terminal of the working vehicle.
Lastly, connect the remaining black clamp, this will need to be connected to a solid metal earthing point and not the flat batteries negative terminal. Be careful of fuel leaks if the vehicle is not in a good condition.
Ensure that the jumper cables are not near any engine parts that will move when you start the vehicle. Before you start the vehicle with the charged battery check that anything that may draw power is off ( Lights, air-conditioning, radios ). The same applies when starting a vehicle with a flat battery.
Now you can start the engine of the vehicle with the charged battery and let it run for a few minutes. Then lightly accelerate and start the vehicle with the flat battery, it should turn over easily.
You will then turn off the engine of the vehicle with the charged battery. The cables will then need to be disconnected in reverse order. First, remove the negative ( black ) cable from the earthing point of the vehicle with the flat battery and then off the negative terminal of the working vehicle. Then remove the red cable ( positive ) from the vehicle with the fully charged battery, lastly remove the clamp from the positive terminal of the vehicle with the flat battery. Bear in mind that it will take some time for the alternator to charge the flat battery so it may be necessary to ride around or let the vehicle idle in your driveway for around 20 minutes. A common cause of a flat battery is having left the lights on for an extended period. Even the parking lights can do this or an interior light.
If you are unable to ascertain the cause you may need to get the battery tested by a specialist. They will advise you whether you need to replace it.
Always keep a set of jumper cables in your vehicle, you never know when you will need them.
Happy motoring, from all of us at Cross Country!