What Car Battery Do I Need?

The UK’s experts on the topic answer the question: “What Car Battery Do I Need?”

Here’s the clearest, simplest possible advice on the net for how to identify the type, size, brand and even which specific model of battery meets your needs.

We provide step-by-step instructions and by the end of you’ll know exactly which battery to get.

Let’s get on with it, then!

Battery buying guide

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What Car Battery Do I Need

Answering: What Car Battery Do I Need

Here at Car Battery Geek, when we started our site, we were astonished by how poor the information is online to help people with making decisions about car batteries. Have you experienced this?

Whether it’s buying decisions or how to deal with problems that arise. Sorry to say it, but we’ve even seen professional mechanics give out advice on car batteries that is not quite right. Their car knowledge dwarfs our, but not when it comes to batteries.

Ta-da! Here, then, is the answer to the question “What car battery do I need?”.

Why are we qualified to talk about this? Well, for the last 21 years (our team members combined) we’ve worked alongside mechanics that see all the problems and issues that arise, we’ve also been to some battery manufacturers, (as in the factories in the far East) and we’ve worked with distributors and wholesalers.

Here’s how to identify which car battery to get.

Step 1: Get the right size

If you happen to know the dimensions of your battery, below we list the UK code for those dimensions. For example, if your battery has dimensions: Length 212mm x Width 175mm x Height 175mm, then your battery size is 063.

If you don’t know the dimensions, don’t worry! We’ll go on to discuss how to identify your battery size even if you don’t know.

Battery Dimensions (mm)Battery Code
242L x 175W x 190H027 (top 027 EFB batteries)
212L x 175W x 175H063 (top 063 batteries)
242L x 175W x 175H075 (Lion 075 review)
278L x 175W x 190H096 (top 096 batteries)
278L x 175W x 175H100 (top 100 EFB batteries, Lion 100 review)
315L x 175W x 175H110
230L x 173W x 222H005
315L x 175W x 190H115
353L x 175W x 190H019 (top 019 AGM batteries)
393L x 175W x 190H020

If you don’t know your battery dimensions, here’s by far the easiest way to find out.

There are online tools that can identify the battery you need according to your car’s make and model, and even better, by your car’s registration plate.

Click here to use the battery finder tool. It will list all the battery sizes that fit your car.

So, great. Now you have a list of batteries that will definitely fit your car.

That still leaves you with one problem.

How do you know which of the batteries on the list are actually right for you, beyond being the correct size? Well, fret no more, ‘cos we’ll give you the advice needed to make that choice too.

Step 2: Identifying the right type of battery for your needs

Okay, so on that list of batteries of the right size, you’ll notice there are 3 different types of battery:

  1. Normal flooded batteries (which is the type used by most cars for many years, and is a standard lead-acid battery
  2. EFB batteries
  3. AGM batteries

We’ll keep this simple. If your car DOES HAVE a stop-start system you must get either of no.2 or no.3 on that list, that is you must get an EFB or an AGM battery.

If your car DOES NOT HAVE a stop start system, then you can choose from 1, 2, or 3. So you can get any of a traditional Flooded battery or a an EFB battery or an AGM battery.

How to choose between Flooded, EFB, or AGM?

All three are lead-acid batteries, they have lead battery plates and an electrolyte solution (a mixture of sulphuric acid and distilled water).

EFB and AGM batteries are upgraded versions, with some improvements in technology.

EFB batteries are better than Flooded batteries, and AGM batteries better even than EFB batteries.

In other words:


Why do we say AGM and EFB batteries are better?

The improvements in the design of both batteries mean that they last 2 to 3 times longer, that is providing as many as 2 to 3 times the number of vehicle starts as normal Flooded batteries.

They’re both more resistant to sulfation (the No.1 cause of death of lead-acid batteries), which is a major reason that they last so much longer.

Because of the improved design of the internal components of the battery, they’re able to provide more starting power. Meaning they’re more reliable for starting your car when it gets really cold in the winter. And even when their charge is depleted, they’ll have more power than a Flooded battery would.

AGM technology is superior to EFB; AGM batteries are the choice for maximum power, reliability and longevity.

Any reason not to get an EFB or AGM battery, then? Well, only that they cost more!

Here’s a guide to car battery replacement costs in the UK.

As you’d expect, an EFB battery is more expensive than a Flooded battery, and an AGM battery is more expensive than an EFB battery.

If your car has stop start functionality:

Then your choice is between two: an EFB or an AGM battery.

Weigh up the cost of the battery and decide if you want to pay the extra for an AGM battery.

Here’s the net’s best comparison of EFB and AGM car batteries.

By the way, if you currently have an AGM battery, you MUST replace it with another AGM battery.

Don’t know if you currently have an AGM battery? Pop open your bonnet and take a look at the battery. If it’s an AGM it’ll say AGM on it pretty clearly, they want you to know it’s an AGM!

If you can’t check your battery for some reason, contact the dealership or seller from which you bought the car, and ask them to confirm if it’s an AGM.

Here are the reviews of the UK’s best EFB batteries. And the UK’s top AGM batteries.

Step 3: Choosing which brand of car battery to get

On your list of batteries of the right size, you’ll see a fair number of different brands and most of them offer AGM and EFB batteries, as well as standard Flooded batteries.

Note: if it doesn’t say EFB or AGM, then it’s a normal Flooded battery.

Now we’ve said that EFB and AGM batteries are superior, but it’s also true that some battery brands are superior quality to others, too. So an AGM battery of a lower quality brand may be more expensive than the normal Flooded battery of a higher quality brand.

So how to make that choice?

Well, we recommend four battery brands: Bosch and Varta are two of the top brands in the world, with extremely well-made batteries, with the highest quality materials. Exide are very solid and reliable batteries, with quality manufacturing. And Lion batteries are the best of the low-cost brands, offering good reliability for the money.

Here’s our analysis of the best battery brands UK.

Choosing the brand and battery type is really a judgement call depending on how much you’re willing to pay for increased quality, reliability and lifespan (UK car batteries lifespan).

For example, let’s say an Exide AGM battery was actually lower cost than a Bosch Flooded battery.

We’d probably go for the Exide AGM, as we really rate AGM technology, even though Exide aren’t as good a car battery manufacturer as Bosch.

But everyone has different preferences. If you know Bosch, then you know they’re one of best manufacturers in the world; maybe you want to choose according to the manufacturer rather than by the battery technology.

Yuasa are similarly high quality, check out our Yuasa Silver 5000 Battery Review.

What Car Battery Do I Need? Summary

That was our answer to the question: what car battery do I need?

We discussed battery sizing and showed you the most reliable and simplest way to find out your battery size; it was to use this ebay battery finder tool.

After identifying the right size, we described the major car battery technologies and how they differ. AGM and EFB batteries are upgrades on traditional Flooded car batteries, which are still the most common. We let you know that if you have start stop system, you have a simple choice between EFB and AGM batteries. And if you have an AGM battery, you have a choice of one type only!

Hopefully, it was helpful with choosing the right car battery for your needs.