How to start a car with a flat battery

How to start a car with a flat battery

Many drivers used to face the situation when the engine was impossible to start because of a dead battery. This often happens when it’s freezing cold  outside or, for example, you have forgotten to switch off the exterior lights or car stereo. The problem of starting the vehicle can be solved by connecting your battery to the battery of another vehicle. For that, you’ll need a set of jumper cables. In this article, we tell you how to hook up jumper cables correctly. Let’s find out what the right order of steps is.

Safety precautions

  • Make sure that there are no children near the place where the procedure will be carried out. If necessary, take them to a safe distance.
  • Read the vehicle’s manual carefully. There are some models which cannot be jump started.
  • When performing the job, wear rubber gloves and protective goggles. Do not touch terminals and metal parts of the car body with bare hands, when they are under voltage.

Which vehicles are unsuitable for jump starting

  • Never jump start a car with another car which has the on-board voltage higher or lower than that of your car. For example, if your vehicle is fitted with a 12 V battery, it should not be connected to a 24 V or 6 V one, in order to avoid voltage surges.
  • It is not advisable to connect vehicles with petrol and diesel engines as their batteries have different cold cranking amps, therefore the process will be either ineffective or risking damage of electronic devices.
  • It is forbidden to jump a car with a faulty wiring, leaking battery, or other defects. Therefore, for instance, if your battery has become flat due to long and unsuccessful attempts to start the engine, seek professional help.
  • It is not advisable to connect to a vehicle with a battery that isn’t fully charged.

How to find out if it is safe to jump start your vehicle?

How to find out if it is safe to jump start your vehicle?
 Make sure your car is in good working order. For this purpose: 
  • Examine the engine compartment. Wires must not be covered with a thick layer of dirt and there must be no cracks or streaks on the battery.
  • Inspect the alternator wires. If they are cracked, voltage is likely not to get to the battery terminals. In that case, jumping car with another battery doesn’t make any sense as the battery of the jump-started vehicle will go flat immediately
  • Try to switch on your headlights, side lights, and ambient lighting. If they switch on and are bright, this means that the battery isn’t the problem, and jump start won’t help to start the car. If the devices listed above don’t switch on and the horn doesn’t work either, then the battery is flat. Sometimes, dim light of the lamps is a sign of a low battery charge.
  • If it is possible, measure the voltage on the battery terminals. If it is higher than 12.6 V, then the battery is ok, and you have to look for a malfunction in other components and assemblies: the starter, starter solenoid, ignition switch, etc.
  • Check whether a strong smell of fuel is coming from under the bonnet. If there is, jump starting your car with jumper cables is dangerous because it can cause a fire.
After that, you should make sure that the battery of the donor car is fully charged. Switch on the headlights or interior lights. The lights should emit bright light. If it is possible, measure the voltage on the battery terminals with a multimeter. It should be 12.6–12.9 V.

16 steps for properly jumping your car

16 steps for properly jumping your car
  1. Park the vehicles opposite each other at a distance of 45–50 cm between them – so that the length of the cables is enough to connect them. Warning: vehicles must by no means contact each other.
  2. In cars with automatic transmission, shift the gear selector into the “Park” mode, in those with manual transmission – into “Neutral”.
  3. Be sure to shut down the engine of the donor vehicle.
  4. Engage the parking brake on both vehicles.
  5. Remove the keys from the ignition switches of the cars, and open the doors in the car with a flat battery. Otherwise, when voltage is supplied, the car’s anti-theft system may trigger on and lock the doors.
  6. Open the bonnet. Find the battery. Its exact location is specified in the vehicle manual.
  7. Examine the battery. Find two terminals. The positive one is usually the bigger one and marked as “POS” or “+”, and the negative one – as “NEG” or “-”. The positive terminal is often coloured red, negative – black. When connecting jumper cables, it is highly important not to mix up the terminals.
  8. If necessary, clean dirt and oxides from the terminals with a cloth or wire brush.
  9. Look at the set of jump leads. The kit should include two cables. One of them is usually red and the second one is black. Note that the cables themselves can be of different colour but the alligator clips on their ends are almost always red and black. This colour marking helps to avoid mistakes when connecting the wires.
  10. Connect the cables in the following order:

    • a red clip– to the positive terminal of the flat battery;
    • the second red clip– to the positive terminal of the donor car;
    • a black clip – to the negative terminal of the battery on the donor car;
    • the second black clip– to an unpainted metal part of the vehicle with the flat battery. It may be a nut or bolt on the engine block.
  11. Make sure that the cables don’t touch the moving parts of the engine.
  12. Start the engine of the donor car and let it run for 10-20 minutes. Stop the engine.
  13. Try to start the engine of the car with the flat battery. If you succeed, don’t switch off the engine for 10-20 minutes. This time should be enough to charge the battery up a little.
  14. If the car doesn’t start, repeat the procedure: start the power unit of the donor car and let it work for some time, shut it down and try to start the other vehicle. Warning: do not switch on the starter of the jump-started car while the donor car’s engine is running: this may lead to the failure of its alternator.
  15. If the start was successful, disconnect the cables in reverse order:

    • black clip – from the negative terminal of the donor car;
    • the second red clip– to the positive terminal of the donor car;
    • red clip – from the positive terminal of the donor car;
    • red clip – from the positive terminal of the battery which was flat.
  16. If, after several attempts, you couldn’t start the engine, visit a garage for help: your battery may be completely depleted, and it will be necessary to restore or replace it, or some other vehicle systems may be faulty. In particular, the engine cannot be started  if the following components are bad:

    • fuses;
    • starter;
    • ignition switch.

How to jump a car without another car?

How to jump a car without another car?

To start a vehicle, you may use a portable starting device – a jump starter. It operates based on lithium polymer batteries, and due to that, despite its compact size, it provides quite high cranking amps. You can buy such a device if, for example, your vehicle is used in harsh conditions, in particular, in areas with cold winters.

The device should be directly attached to the battery terminals. When doing this, it is also very important to observe the polarity. For more detailed information on how to properly connect jumper cables, read the jump starter manual carefully.

 Usually, it is necessary to do the following steps: 
  1. Connect the red cable which comes together with the device to the positive terminal of the battery.
  2. Connect the black cable to the negative terminal of the flat battery.
  3. Insert the connectors of the other ends of the cables into the corresponding outputs on the portable starting device.
  4. Select the required mode of the jump starter and switch on the device.
  5. Start the engine.


A discharged battery is a problem which even experienced motorists may encounter. That’s good that it can be solved by a relatively simple method – jump starting. All you need is a set of jumper cables and another battery. By following all the above tips you can easily jumpa car with another battery even if you’ve become a driver not so long ago.


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