If you have a flat battery, you can start the car by using jump leads to connect the flat battery to a charged one, whether or not it’s fitted to another vehicle. Here’s a guide on how to jumpstart a car battery, assuming that the charged battery is fitted to another vehicle.
Be wary when jump starting cars with engine management systems – careless jump starting, particularly if the leads are allowed to spark, can cause damage to the car’s electronic components. Some cars, such as certain BMWs, are fitted with special connectors to allow jump starting, and on these cars the jump leads should only be connected to the special terminals provided.
It’s also worth noting that the cable connections for jump starting often allow only limited current flow. Depending on how much the battery’s discharged, jumper connections may or may not start a vehicle with a weak battery. It’s a good idea to read your car’s handbook carefully to see if there are any special recommendations to be observed when using jump leads. If in doubt, call one of the breakdown services, as they will have the equipment to get your car running without any risk of damage.
Step by step how to jumpstart your car battery
1 Position the vehicles so that the jumper cables will reach. But, MAKE SURE THE VEHICLES DON’T TOUCH EACH OTHER!
2 Make sure the transmission is in Neutral (manual) or Park (Automatic).
3 Make sure the ignition switch is in the Off position.
4 Turn off the lights and other electrical loads. Note: If the vehicle you want to start is equipped with a computer, it’s a good idea to turn on the heater blower motor. This will prevent damage to the computer in case of an excessive electrical surge.
5 Make sure the booster battery is the same voltage as the dead one in the vehicle.
6 Your eyes must be shielded. It’s a good idea to wear safety goggles.
7 If the booster battery has removable vent caps, remove the caps and lay a cloth over the vent holes.
8 Make the jumper cable connections EXACTLY as follows:
a) Connect one end of the red jumper cable to the positive terminal of the discharged battery and the opposite end to the positive terminal of the booster battery;
b) Connect the black jumper cable to the negative terminal of the booster battery and then to a bolt or bracket on the engine block - NOT to the negative battery terminal - of the vehicle being jump started. This is an important precaution to prevent sparks which may cause an explosion.
9 Check the cables - make sure they’re not going to be in the way of the fan, drive belts or any other moving parts when the vehicles are started.
10 Start the engine of the vehicle with the good battery and run it at a moderate speed.
11 Start the engine of the vehicle with the discharged battery.
12 Reduce the engine speed to idle on both vehicles and leave all switches off to prevent damage to the vehicle electrical system.
13 Remove the cables in the reverse order they were attached.