By Shell on Oct. 12, 2021
A flat battery isn't the only reason for a non-starting car, but if you turn the key and nothing happens, or that familiar starting 'chug' progressively slows and dies, it's a likely suspect. So, time to call roadside assistance? Maybe not yet. If you have jumper leads and access to another car for a few minutes, you might be able to get back on your way again. Here's how to do it.
1. Locate batteries in each car
They'll probably be under the bonnet but might be in the boot or elsewhere – check the owner's manual if you're unsure. Check each battery. If you see damage, corrosion or fluid leaking, you're safer calling in roadside assistance, rather than risk suffering an acid burn or shock from the battery.
2. Position cars
Park the cars so the jumper leads can reach both batteries. They'll need to be close, but make sure they're not touching or serious electrical damage could result. Put them in park (or neutral if the car is a manual), apply their handbrakes and turn them off.
3. Attach jumper leads
You should only use jumper leads with built-in surge protection, which are designed to protect the delicate electronic systems in today's cars from a potentially damaging power spike. This process is simple and safe so long as each step is followed to the letter:
a) Clamp one end of the red positive jumper lead to the positive terminal of the dead battery (look for the '+' symbol).
b) Clamp the other end of the red positive lead to the positive terminal of the good battery.
c) Clamp one end of black negative jumper lead to the negative terminal of the good battery (look for the '-' symbol).
d) Clamp the other end of the black negative lead to some clean, unpainted metal on the dead car's engine block, well away from the battery. Don't attach it to the negative terminal – this could result in sparking or an explosion.
Be careful during all steps to ensure the black and red clamp ends never touch as this will result in sparking. Also make sure none of the leads are at risk of getting caught in moving engine parts.
4. Revive/start dead car
Start the good car and let it idle for a few minutes to charge up the dead car's battery, then fire up the dead car. If your problem was a battery issue, it should start. Don't turn it off yet.
5. Remove jumper leads
This needs to be done in the exact reverse of how you attached them. So first, the end of the black negative cable attached to the dead car's under-bonnet metal, then the other end of same cable to the good battery's negative terminal. Next, the red positive cable from the positive terminal of the good battery, then finally the other end of that cable from the positive terminal of the previously dead battery.
6. Drive revived car
That previously flat battery needs time to recharge or it may well fail to restart the engine the next time you need it, so take it out for a good 20 to 30-minute drive.
A battery jump starter or 'power pack' can be stored in the boot and will save you having to rely on another car for help – but they do cost a lot more than a set of jumper leads and need to be kept charged.
If you drive a manual vehicle and have some willing hands who'll help push your car (or are on a hill), it's possible to 'bump start' your car using nothing but its momentum. Simply turn the key on/run, dip the clutch and get the car rolling. Once you're doing about 5-10km/h, quickly pop the clutch out and the engine should start.