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What To Do When Your Car Battery is Flat

Posted by Rebecca Parsley on

It’s one of those frustrating situations we’ve all encountered. Your car has been running with no problems, then one day you get in, turn on the ignition, and nothing happens. Your battery is dead, and you’re not going anywhere.

Vehicle recovery organizations say most home call-outs from their customers are due to a flat car battery, so you’re not alone. There are a couple of options you can try to get the engine running before you resort to professional assistance, however.

Why is my car battery flat?

Car batteries die for various reasons. A common one is because the headlights, interior lights or indicators have been left on without the engine running, although many modern cars now have audible alerts. Running the air conditioning with the engine switched off will also deplete the battery.

Not starting your car for long periods can cause the battery to drain, while low air temperatures can cause it to freeze. Lack of maintenance, such as not keeping the terminals clean, can also lead to problems or there could be a mechanical issue that has stopped the alternator charging the battery while the engine was running.

Try a jump-start

The easiest way to start a car with a flat battery is by using jump leads, or jumper cables. It’s a good idea to buy a set and keep them in your vehicle; that way, you’re not relying on someone else to supply them. Basic cables are inexpensive and readily available from most auto stores or online; then, all youi need is another car. Longer-length cables are useful in case it’s not possible to park the second car right next to or in front of yours.  

  1. First, open the bonnet and check your battery for any visible damage. If you can see it is cracked or leaking acid, you should not try to jump-start your car.
  2. Make sure both vehicles are in neutral, with the ignitions switched off and the handbrakes on.
  3. Identify the positive terminal on each car battery; it may be marked with ‘POS’ or the + symbol, or it will be larger than the negative terminal. Take the red jump lead and attach the clip on one end to the positive terminal on your battery, then repeat the process on the other car’s battery.
  4. Take the black jump lead and attach one clip to the negative terminal on each battery.
  5. Start the engine on the other car and let it idle for a couple of minutes before you try and start your own car. Most times, this will be all that’s needed to fire your engine into life; if not, check the cables are connected correctly and try again. If your car still won’t start, it may mean your battery is beyond help.
  6. When your engine starts, don’t shut it off again! Leave it connected to the other car for a few minutes to transfer energy to your battery. Then, still with your engine running, carefully disconnect both cables from your vehicle. Make sure the clamps don’t touch as this will cause a potentially harmful short circuit.
  7. Once your battery is disconnected from the cables, you can close the bonnet. Remove the cables from the other car and switch off its engine. (Yours should still be running.)
  8. You’ll need to recharge your car battery fully before you turn off the ignition. Drive around for at least 20 minutes, longer if possible. Alternatively, leave the engine running for a while where it is.

What if no jump leads are available?

It’s possible to jump-start a car without cables in certain situations. It should have standard, not automatic, transmission and ideally there’ll be a downward slope or incline nearby. If you have some willing friends or neighbors, you could try this on a flat road.

  • Push the clutch pedal down completely, put the car in first gear, and turn on the ignition.
  • With the clutch still fully depressed, release the handbrake or take your foot off the brake pedal.
  • Allow the car to start rolling down the hill or ask your helpers to start pushing it forwards, gaining as much momentum as possible.
  • Once you reach 10-15kmh/6-10mph, release the clutch quickly. You’ll feel your car jolt and the engine should turn over and start. If not, depress and release the clutch a few times until it catches.
  • Again, you’ll need to drive the car around for a while or leave it standing with the engine idling to fully recharge your battery.

What if it happens again?

If your engine refuses to start again next time you use it, your battery is failing to hold charge and should be replaced. You can buy testing devices to check your car battery at home if you are concerned, or many auto centers will do this for free.