How a car’s battery works

Battery removal and replacement image

A car’s battery, like all batteries, stores electrically charged energy in the form of chemicals. Car batteries use lead-acid technology and are designed to last for many years but they’re not like cell phone batteries and don’t like to be repeatedly drained and charged. So if you run it down by leaving the lights on or have a ‘mystery drain’ somewhere else in the car, it’s likely that your battery won’t be in the best of health.

This is an easy task and requires only basic tools. In most cases this procedure will take only half an hour or so.

Every car is different, so before you view the full instructions, find yours…

When to change your battery

It’ll be obvious when your battery is flat: the central locking may not work and the engine won’t turn over. However, it’s not always easy to know when the battery needs to be replaced. Once the car has been started (via jump leads/jumper cables, bump started or battery trickle-charged) take the car for at least a 20-minute run to charge the battery. Turn off the engine and restart it the next morning. If it’s flat again you need to investigate further.

First, check the battery leads are secure. Then check the battery’s state of charge by either looking at the indicator eye (not present on all batteries), sampling the electrolyte in a battery hydrometer (not possible on sealed batteries) or perform a battery load or drain test with a suitable meter. If you need to change your battery, Haynes will walk you through all of the necessary steps.

All cars are slightly different, so if it is time to change your battery, use our before you begin checklist, and find your car for specific instructions.

Warning

Make sure you follow the correct battery disconnection procedure to avoid causing problems with the car's electrical components

How to change your battery

This is a clip from a sample video. Find the full step-by-step task for your model

A very brief summary of the task:

  1. Undo the clamp nut and remove the cable from the negative terminal first and then do the same on the positive terminal
  2. Undo the battery hold-down clamp or bracket and lift out the battery. Be careful, it’s heavy
  3. Examine the battery tray and clean it if necessary
  4. Install the new battery, fitting the hold-down clamp(s) and secure the positive cable before the negative cable

Why you should change your battery

Aside from the obvious inconvenience of being stranded somewhere without leads or someone to give you a bump start, a dead battery may require you to reset the car’s systems, such as the throttle position sensor, audio system and more. This is time-consuming and we strongly recommend fitting a new battery as soon as possible.

Before you begin

Tools you will need

Only basic tools are required for this job

  • Socket set

Parts you may need

  • Battery
  • Battery tray
  • Battery retainer

How much does a new battery cost?

Battery £50-£200

 

Every car is different, so before you view the full instructions, find yours…