What to Do When Your Car Battery Is Dead

Ellie Dyer-Brown, 4 months ago

5 min read

  • Battery
  • Car ownership
Looking under car hood image

WhoCanFixMyCar discusses what causes flat batteries and what to do if yours dies.

If you own a car long enough, you will encounter a flat battery at some point - it's an unfortunate fact of life. This guide explains why it happens and what you can do about it.

Guide Contents:

How to tell if your battery is dead

What are the symptoms of a dead battery

What to do if your car battery is drained

How to jump start a car with a dead battery

What causes a car battery to die?

Why won't my dead battery start with a jump?

Find a mechanic to diagnose or fit your battery


How to tell if your car battery is dead

If your car doesn’t start, it could be that the battery has died. Most batteries need to be replaced every three to five years, and if you have an older battery, you may notice that it doesn’t hold charge as well as it once did. For example, your engine will struggle to start in very cold or hot weather. In this case, the best thing to do is to replace the battery before it goes for good.

Woman checking car battery.

However, if your battery goes flat unexpectedly, check to see if you’ve left an interior light or your headlights on. Apart from old age, this is the most common cause of a flat battery.

Worried something else might be the problem? Here are eight possible reasons your car won't start.


What are the symptoms of a dead car battery?

There are three major signs to look out for.

The first is trouble starting your car. The engine might crank more slowly than usual and take a long time to get going.

Secondly, you might lose electrical power within your car. The battery doesn’t just power the engine - it also powers things like your radio, electric windows and heaters. If these things stop functioning as they should, it’s a sign that your battery is on its way out.

The final and most obvious sign is a dashboard warning symbol resembling a battery. It could indicate a failing alternator, loose starter terminal or damaged cabling. However, if the light stays on while you’re driving, it’s probably due to your alternator belt, which is responsible for charging your car’s battery.


What to do if your car battery is drained

The answer to this question entirely depends on why your battery is flat. If it’s old or faulty, you’ll need to replace it. With the right know-how and tools, you can do this at home, but the quickest and safest option is to get a trained mechanic to do the job.

Technician fitting a car battery.

On the other hand, if your battery has been drained because you accidentally left a light or the radio on, you have two options. You can either jump-start your car or purchase a car battery charger which plugs in at home.


How to jump start a car with a dead battery

Here are the steps you need to take to get moving again when your battery dies.

Remember, you need to be extremely careful when dealing with high voltages. If you see that the battery is cracked and is leaking acid, DO NOT ATTEMPT to jump-start the car, as you will be putting yourself in danger.

Step 1

Park the car with the dead battery nose-to-nose or parallel to the another car and open the bonnet of each vehicle.

Step 2

Take the red positive jump lead, connect one end to the positive terminal on the dead battery (as shown below) and the other end to the positive node on the live battery on the other car.

Step 3

Do exactly the same using the black cable, attaching each end to the negative nodes.

Step 4

Start the engine of the rescue car and allow it to run for roughly ten minutes. This will charge the dead battery of the other car.

rsz screenshot 7

While the rescue car is still running, attempt to start the engine. If it doesn't work, leave the car for a few more minutes and try again. If this does not yield results in 30 minutes, another problem will likely be preventing your vehicle from starting.


What causes a car battery to die?

There are several reasons a battery could die. The most common are:

  • Leaving your headlights, interior lights or radio running for prolonged periods while your car is stationary.

  • If you don’t use your car for a long time, the battery will die as it won’t get charged by the engine.

  • The failure of the diode bridge or voltage regulator in the alternator. This is down to the fact that the alternator is responsible for charging the battery when the car is running. If it malfunctions, the battery will die.

  • If the temperature drops well below zero degrees, the battery could freeze.


Why won't my dead battery start with a jump?

If your battery is dead and can't be jump-started, you will need to find a local car battery specialist garage or mechanic to diagnose the problem and potentially carry out a replacement.


Find a mechanic to diagnose or fit your battery

Fitting a new battery.

WhoCanFixMyCar's garage network is full of mechanics who can help you get back on the road in no time.


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Written by Ellie

Ellie Author Pic

Ellie is WhoCanFixMyCar’s Content Writer. She has a BA in English literature from Durham University, a master’s degree in creative writing, and three years of experience writing in the automotive industry. She currently drives a Suzuki Swift.

Find Ellie on LinkedIn.