A dead battery is a pain. However, you need to investigate whatever’s caused the battery to drain in the first place if it’s anything other than leaving your lights on.
When faced with a dead battery, a jump start is the best way to get going.
What you need to achieve this is a set of jump leads and another person willing to donate the power in his/her good battery to transfer across into yours.
Having acquired these two essential ingredients, the process is normally easy and quick:
1) Park the cars with the two batteries facing each other and about two feet apart so that the jump lead can stretch from one battery to the other. An automatic car should be in ‘park’ and a manual car should be in neutral with the handbrake on.
2) Turn off both engines and remove the ignition keys. Visually check that neither battery is showing signs of corrosion. If corrosion is evident, the affected battery will need to be replaced before the jump starting can begin; indeed, the jump starting may not be needed if the corroded battery (when replaced) is the one that’s failed in the first place!
3) Assuming that corrosion isn’t an issue, the secret is to connect the two positive terminals of both batteries and then the two negative terminals. The positive terminals will have a + sign alongside or be colour coded red and the negative terminals will have a – sign alongside or be colour coded black. The jump cable will carry similar colour coding. It’s critical, though, that the metal ends of the jump cable don’t touch each other as the batteries could be damaged.
4) Now for the connections. Start by attaching one end of the red cable to the positive/red terminal of the dead battery and attach the other end to the positive/red terminal of the good battery. Now, attach one end of the black cable to the negative/black terminal of the good battery and the other end to an unpainted part of the metal car body or engine block, avoiding any parts that move like fans or belts. It’s critical that you remember this connection sequence as it will be necessary to disconnect in the exact reverse order when the job is completed.
5) Now, start the engine of the good battery and slightly rev the engine for a few minutes to maximise the power in available to transfer across. Now, try to start the car with the dead battery. If successful, rev the engine and let it run for a few minutes. If unsuccessful, let it rest with the good car still ticking over and check the connections. Then, attempt to start the other car again but, if again unsuccessful, a replacement battery will be needed or a tow rope/truck.
6) If the previously dead car is now successfully running, continue to increase the revs of both cars for a few minutes to maximise the power transfer. Then, and this is extremely important, disconnect the cables in the reverse order to the connection sequence, again ensuring that the cable ends don’t touch each other until all connections have been removed.
7) The previously dead car now needs to be driven for a while to boost the power in the battery as much as possible. If the problem was caused by a known problem (e.g. leaving lights on) then that should end the matter. If, however, there was no obvious reason then it’s vital that the battery’s checked by a mechanic as it could be faulty and need replacing to prevent the problem recurring.