How to jump start a car: how to handle a flat car battery using jump leads or a push start

Monday, 4th January 2021, 9:20 am
Updated Monday, 4th January 2021, 9:21 am

Coming out to start your car only to find the battery flat is one of those "why now?" moments most drivers face at least once.

Whether it's due to a car sitting idle for a prolonged period or a bigger underlying issue, batteries can lose their charge, leaving you unable to start your vehicle and potentially ruining your day.

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Despite it happening to millions of motorists every year, a poll of drivers by Halfords found that a third don't know how to check their battery while even more don't know what to do if it's flat. Worryingly, 11 per cent don't even know where their car battery is (check your handbook if you're one of them).

With the prospect of problems being made worse by cold weather and lockdown restrictions, knowing how to jump start your car is a useful skill, so here are the simple steps you need to take if you car’s battery has lost its charge.

Using jump leads


First check your battery isn’t leaking or damaged. If it is, don’t attempt to jump start it - it’s time to get a replacement.

  • Position the two cars so their engine bays are close together but the cars aren’t touching. Move any loose metal objects away from both batteries and remove any loose clothing that could get caught and any metal jewellery.
  • Connect one end of the red jump lead to the positive (+) terminal of the working car’s battery, then connect the other end to the positive (+) terminal of the flat battery.
  • Connect one end of the black jump lead to the negative (-) terminal of the working car’s battery and the other end to an earthing point on the other car - this needs to be a solid, paint-free metal point such as a bolt or bracket away from the battery.
  • Remove the leads in the reverse order to which you attached them. Make sure they don’t touch any metal surface or get caught in any moving parts.

If your car won’t start after following these steps you battery has most likely failed completely, in which case you’ll need a new one. And if it won't charge after starting it could be a sign of alternator problems that will need professional attention.

Bump starting

This method isn't as safe or reliable as using jump leads so we'd recommend avoiding it unless you're absolutely desperate. It also only works on cars with manual transmission. For this you'll need a couple of helpers to push the car.

  • Get your helpers to start pushing the car, making sure it's safe to do so.
  • Once it's running, stop but let the engine run for at least 15 minutes to put some charge back in the battery.
Bump starting is more difficult and less reliable than using jump leads (Photo: Shutterstock)

Tips for avoiding a flat battery

The RAC offers the following advice to help protect against a flat battery,:

  • Park your vehicle in a garage whenever possible
  • Ensure everything is switched off when you finish your journey including lights, heater, fan, heated rear windscreen, radio etc. Sat navs and other devices can also drain the battery if left connected – every volt is precious first thing in the morning
  • Check the battery connections, ensuring that they are tight and free from any corrosion. And, don’t forget that battery acid is highly corrosive to skin and paint work
  • Take your vehicle for a decent drive to get your battery well charged, and get the engine to its proper operating temperature, before you really need it – ideally several days before. Don’t just check that it starts as this is likely to drain the battery more