Thursday Tip: How to Jump Start Your Car

and why sometimes it is best not to!

Jump starting your car can be an easy way to get it going if the battery is flat. However, if they are not used correctly then using jump leads can cause damage not only to the leads but more critically to the car’s electronic systems and the Electronic Control Unit (ECU).

Therefore, if you feel comfortable in doing it yourself then look at the advice below on how to do it correctly, consult your car’s handbook or alternatively give a call to the roadside assistance companies or your insurance company and they will organise a trained mechanic to come out to you. 

We will go through:

  • What you’ll need to jump start a car
  • Jump lead safety
  • Step-by-step guide to jump starting
  • How to use a battery booster pack
  • What to do after a jump start
  • How often to change a car battery?
Car Battery inspection and test at Oliver's Car Services in Gorey

Using jump leads

What you’ll need to jump start a car:

  • A pair of working jump leads that are of a suitable strength to take the charge that is going to go through them. All jump leads are marked with a rating that shows the maximum amount of charge they can take. Using a set of leads that are rated too low will mean that you are putting through them a charge that is too powerful and this could lead to heat being generated or arching of the leads leading to the terminals touching and severely damaging both cars.
  • The vehicle with the flat battery, which needs to be in a spot where jump leads can easily reach the battery. Avoid the two leads touching at all as this can lead to them shorting out.
  • Another vehicle with a fully charged battery. HOWEVER, never use a hybrid or electric car to be the donor car when jump starting another car as this could lead to serious damage).

Using jump leads safely

 

Before you try to jump start a car, remember that batteries produce flammable gases. Here’s how to stay safe:

 

  • Check the battery – pay particular attention to the battery terminals to see if they are corroded or have an acid build up on them, never try to jump start a battery that looks damaged or is leaking. Check out the battery mount and see if the battery is secure and that the cables are attached securely to the top of the battery terminals, again if the battery or the terminals are loose then we recommend that you DO NOT jump start the car.
  • Check the jump leads – Make sure that the jump leads you are using are rated high enough for use on the car and the battery that you are jumping and the car and battery you are using as the donor car. The battery will tell you the rating it has on the top. If you are unsure whether the jump leads are suitable for the car, or the battery then DO NOT try to jump start the car.  Check also to see if the jump leads that are damaged or cracked in anyway, if they are then please get a new set of jump leads before you try.
  • Stop using the jump leads if they get hot or if you see sparks at any time – this means that there is a major problem and by continuing you could cause severe damage to not only the car but also yourself.
  • Do not remove jump leads whilst the engine is still running – this might sound a bit counter intuitive but removing jump leads from an engine that is still running can cause serious damage to the car’s electronic systems. A car’s electronic system is designed to have a certain voltage and current running through it and if this drops or increases very quickly then the car’s electrical system will be unable to cope.
Car Battery inspection and test at Oliver's Car Services in Gorey

Make sure the environment is safe

 

Before you start:

  • Remove any loose clothing or objects as these could get caught up in the moving parts of the engine.
  • Don’t let any metal objects touch the car batteries – these could cause a spark and possibly make the battery explode. That includes rings, necklaces, watch straps, hand tools, clips, stray wires etc.
  • Never smoke or allow naked flames anywhere near either battery.
  • Make sure you know which are the positive (+) and negative (-) terminals of both cars’ batteries before you start

A step-by-step guide to jump starting a car with jump leads

 

Find someone with a car who’s happy to help. Their car must have a fully charged battery with the same voltage as yours which is usually 12 volts.

 

Line up both cars

  • Park both cars so that their batteries are within easy reach of one another, without the cars touching and without the jump leads stretching to reach the battery terminals.
  • Put and keep the handbrakes on and the ignitions off on both cars.

 

Connect the RED jump lead

  • Use the red jump lead to connect the working battery’s positive (+) terminal to the flat battery’s positive (+) terminal. Always connect from the working to the flat.

 

Connect the black jump lead

  • Take the black jump lead and attach it to the negative (-) terminal on the working battery.
  • Then attach the other end to an earthing point (unpainted metal on the engine block or chassis) well away from the flat battery and fuel system. If you are unsure as to what an earthing point or if you can get a good connection, then please DO NOT attempt to jump start the car.

 

Starting the car with the working battery

  • Keep both engines off and wait for 3 minutes, then start the working car’s engine and let it run for 1 minute.

 

Starting the car with the flat battery

  • Turn on the engine in the car with a flat battery.

 

Let both cars run

  • Leave both cars to idle at a fast pace for around 10 – 15 minutes.

 

Turn off both cars’ engines

  • Turn off both cars’ engines

 

Remove the jump leads

  • Remove the jump leads in the reverse order to how you attached them:
  • Switch off the engines on both vehicles.
  • Take the black jump lead off the earthing point.
  • Remove the other end of the black jump lead from the working battery’s negative (-) terminal.
  • Disconnect the red jump lead from the working battery’s positive (+) terminal.
  • Remove the other end of the red jump lead from the positive (+) terminal on the flat battery.
  • Make sure the leads DO NOT touch one another, OR either car, as you remove them.

 

Restart your car

  • Try turning the keys in the ignition to see if your car will start up, it should start straight away. However, if it does not start then this more than likely means that there is a more serious problem with the car that requires professional assistance.

 

How to jump start a car with a battery booster pack

 

It can be a good idea to keep a car battery booster pack in your car. That way, you can jump start your battery even if you can’t get another car to help you. There are a number of booster packs available on the market either online or from your local auto factors shop.

Similar to using a car to jump start another car there are a number of steps that you need to go through to jump start a car with a booster pack.

 

Before you start, make sure:

 

  • The car battery doesn’t look damaged and isn’t leaking, check out the section above on checking the battery
  • Make sure the environment is safe and that you have taken off any loose clothing or metal jewellery or watches and removed any metal items from the area and the car.

    Steps to using a car battery booster

     

    Check the battery booster

    • Make sure the pack’s fully charged
    • Put the battery booster pack somewhere stable. Do not put it on the engine as it might fall off when the engine starts.

     

    Connect the red jump lead

    • Connect the red positive (+) jump lead from the battery pack to the positive (+) terminal of the car battery.

     

    Connect the black jump lead

    • Connect the black negative (-) jump lead to an earthing point on your car. Unpainted metal on the engine block or chassis is best.

     

    Switch on the pack

    • Once the battery pack’s connected, switch on the pack. Check to see if the lights come on of the dashboard of the car

     

    Try to start the car

    • Try to start your car by turning the key in the ignition.
    • Try turning the keys in the ignition to see if your car will start up, it should start straight away. However, if it does not start then this more than likely means that there is a more serious problem with the car that requires professional assistance.

     

    Let the engine run

    • If the car starts, keep the engine running for about 5 minutes.
    • After 5 minutes, switch off the boost pack and allow the engine to run for a further 5 to 10 minutes.

     

    Turn off and disconnect

    • Turn off the engine.
    • Remove the leads in the reverse order to how you placed them on (first disconnect the black lead, then the red lead).

     

    Restart your car

    • Try turning the keys in the ignition to see if the car starts up again.

    What to do after you’ve jump started your car

     

    If you’ve managed to jump start your car, the engine will need to recharge again fully. Usually, you can charge the engine by driving normally (not in stop-start traffic) for at least 30 minutes or to supplement this or if normal driving is not possible you can also use a portable car battery charger to top up the charge on your battery.

    How often should you change a car battery?

     

    Car batteries, on average, last between 5 and 7 years but you should only consider changing a car battery when it’s showing signs of deterioration.

    If the battery’s more than 5 years old and seems like it’s struggling to start the car then get it checked out as it is far better to be safe than sorry.  One-in-three breakdowns are caused by faulty batteries and one-in-four batteries tested are found to be faulty. So if your car is struggling to start then get it sorted as it will be more than a minor inconvenience if it breaks down on the roadside or  on a cold morning when you’re already late for work.

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