The vehicles must not be in contact, otherwise current might flow as soon as the positive terminals are connected.
The cable clamps must not be allowed to contact each other when one end of the jumper cables are connected to a battery.
Ensure that tools or conductive jewelery (rings, chains, watch straps) do not come into contact with the positive jumper cable or the positive battery post.
Improper hook-up of jumper cables can ruin the alternator.
Battery Acid Leakage
Do not lean over the battery due to danger of chemical burns from leaking acid.
Battery Charging and Jumping Hazards
Improper use of booster battery to start a vehicle may cause an explosion.
Keep sources of ignition away from the battery, e.g. naked flame, burning cigarettes or sparks due to cable contact.
Before connecting jumper cables, it is essential to thaw out a frozen battery.
Connect jumper cables in the following sequence: Always observe the sequence below:
Connect the positive lead (red) to the positive terminal of the discharged battery first, then connect it to the positive terminal of the donor battery.
First connect the negative cable (black) to the negative terminal of the donor battery, then connect it to a suitable grounding point on the vehicle with the discharged battery.
This grounding point must lie as far as possible from the battery.
A solid metal part, for example, would be a suitable grounding point.
If no suitable grounding points are to be found on either vehicle, the negative cable must carefully be connected directly to the negative terminal of the battery.
If a suitable grounding point is to be found only on the donor vehicle, the negative cable must first be connected to the terminal of the discharged battery, then to the grounding point of the donor vehicle.
Run the engine of the donor car at a higher speed.
Start the engine.
An attempted start using jumper cables should not last more than 15 seconds. Then allow a waiting period of at least one minute.
Before disconnecting the jumper cables, electrical loads such as the heated rear window and the heating fan blower should be switched on (the vehicle's lights must not be switched on). This reduces voltage peaks which may occur when disconnecting the jumper cables.
With the engine running, remove both jumper cables in reverse order.