How to Jump Start a Flat Car Battery

A flat car battery can spell disaster, especially on cold mornings when you're already late for work! Here's the easy way to jump start your car if your car key isn't doing the job for you.

SAFETY TIP: Before you attempt to jump start a car, check that:

  • The battery isn't leaking or damaged - seek help if it is
  • That there are no naked flames including cigarettes nearby
  • All clothing and metal items like jewellery are well out of the way of the battery
  • The key is out of the ignition

Once you've checked those, you're ready to go!

What do I need?

  • Two jump leads - a black 'negative' lead and a red 'positive' lead
  • Another car with a charged battery
  • Gloves and goggles for extra safety

Steps to jump start a car

STEP 1: First, you'll need to park the car with the fully-charged battery so that it’s facing the car with the flat one. Leave enough space between the two so that you can open both bonnets and connect your jump leads to each battery.

STEP 2: Once you're in position, put your gloves and goggles on and attach the red 'positive' lead to the positive battery terminal on the working car. Look out for a '+' symbol next to the terminal. Then, connect the other end of the red lead to the positive terminal on the flat battery.

STEP 3: Once the red cable is connected, grab the black 'negative' one and connect one end to the negative terminal on the charged battery (the one with the '-' next to it).However, do not attach the other end to the negative terminal on the dead battery. Instead, clip the clamp onto a piece of solid metal away from the fuel system and battery. Some cars will have a specific area known as an earthing rod, so check your owner's manual to see if your car has one of these.

STEP 4: Now that you have all four ends of the jump lead cables attached, wait five minutes. After you've done this, start the engine of the car with the charged battery and let it run for a minute. Leave it running, and then try and start the car with the flat battery. If it doesn't start within five minutes, wait another couple of minutes and try again.

STEP 5: Once the car with the flat battery is running, leave both car engines on for 10 minutes. Then, remove the cables in reverse order (shown below). Just make sure you don't allow the clamps to touch any metal or each other as you take them off:

  1. Black lead attached to car with flat battery off
  2. Black lead attached to car with charged battery off
  3. Red lead attached to both cars off
  4. All leads fully detached from the car, taking care not to touch other metal components when removing.

STEP 6: Leave the car with the newly charged battery running for 20 minutes or so, then take it for a 30-minute drive before parking it up again. Your battery should now be fully charged and the engine will hopefully start up first time the next time you want to drive!

STEP 5: Once the car with the flat battery is running, leave both car engines on for 10 minutes. Then, remove the cables in reverse order (shown below). Just make sure you don't allow the clamps to touch any metal or each other as you take them off:

  1. Black lead attached to car with flat battery off
  2. Black lead attached to car with charged battery off
  3. Red lead attached to both cars off
  4. All leads fully detached from the car, taking care not to touch other metal components when removing.

STEP 6: Leave the car with the newly charged battery running for 20 minutes or so, then take it for a 30-minute drive before parking it up again. Your battery should now be fully charged and the engine will hopefully start up first time the next time you want to drive!

If you're still struggling to start your car, I should be your first point of call before contacting a mechanic. It may be the battery is old and beyond regenerating, or the alternator isn't operating correctly. In either instance, as your handyman it is within my capabilities to replace.