Understanding the battery basics

A car battery has a shelf life of anywhere between 3 to 5 years. Many come with a guarantee, so be sure to check your original purchase or dealership receipt to find out if you’ll have to pay for a replacement or if your faulty or failing battery is covered.

So: “Which battery for my car?” It’s a common question. When choosing a new battery, there are hundreds of different sizes and brands to pick between. A lengthier guarantee or well-known brand are often sensible options to help with your decision.

Prices will vary too, and with a new battery, picking the cheapest one available can be asking for trouble.

Finding your battery type by registration

There are hundreds of online car battery finder pages. All you have to do is type in your registration number, and you’ll see the correct group code or a selection of different batteries that are suitable for your vehicle. You should be able to determine the size and power if you’re planning on using the information to shop around for the best deal.

With so many online databases available, it’s easy to track down the correct type of car battery by reg.

Choosing the correct battery – fitting criteria

  1. Battery group codes – the correct battery group codes are in your owner’s handbook, or if replacing like-for-like, should be available on your existing battery.
  2. Determine the dimensions – Measurements are in mm and are LxWxH.
  3. Consider the terminal layout – Looking at the front of the battery, its terminals could be at the front or the rear of the battery with the positive terminal at the right or left-hand side.
  4. Decide the terminal type – There are 4 types of terminal; each will correspond with your battery connectors:
    1. Standard UK post – are the most common
    2. Japanese post – have a narrower negative post than the positive
    3. Lug terminals –are square posts with a bolt-through hole
    4. Side terminals – just as the name suggests, these are located on the side of the battery

Battery power

Battery power is determined by two settings: its cold cranking amps (CCA) and its reserve capacity (RC).

Cold cranking amps (CCA)

This rating lets drivers know how well the battery starts the car in cold conditions. Starting your car and your battery’s performance is hindered in cold-weather situations. This figure is the number of amps your 12-volt battery can deliver at 0°F for 30 seconds, maintaining a voltage of 7.2v.

If the CCA figure is significantly higher than recommended by your vehicle manufacturer, it isn’t always the best battery for the job. If you can’t match the CCA exactly, one slightly higher is preferable to one marginally lower.

Don’t confuse a battery’s CCA with its CA (cranking amps). The cranking amps measure is taken at 32°F instead of zero, so provides a higher count.

Reserve capacity (RC)

Your battery’s reserve capacity is the time a fully charged new battery will operate if the alternator fails. Usually, it’s the vehicle’s alternator that converts power from the engine into the electricity it uses to keep the car moving.

If you’re looking for the numbers behind the science, this is how long the battery will deliver 25 amps at 80°F without falling below the car’s required minimum voltage.

C20 capacity

Not all batteries will display this, but those that do, indicate how much energy is stored in the battery. The C20 capacity is measured in ampere-hours (Ah).