What Amp Car Battery Charger Do I Need?

Car Battery Charger Amps: How Many Do I Need?

Fortunately it’s not that difficult to work out how many Amps you need to charge your car battery.

Here’s exactly how to get the right size of charger.

1) Get the capacity of your car battery (in Ah)

Most of the time, it’ll be written on your car battery.

It’s the number of Amp-hours the battery can deliver, and is expressed as a number of Ah (what does Ah actually mean, though).

Don’t confuse it with the CCA (or EN) number, that’s different.

What if I can’t see the Ah written on the 12V battery?

That’s okay, you still have some other options to find out the battery capacity.

The make/model method

1. Take a look at your car battery and find out the battery make/model – most batteries will very clearly show the make and model on them.
2. Google that make/model, then you will see the capacity.
3. For example, if you have a Lion 096 car battery, then you can Google that and you will see that the capacity is 70Ah.

The “battery finder” method

If there’s no way for you to identify the make and model of the car battery type you have, and therefore no way to know exactly what the capacity of the battery is, don’t worry.

There’s still another solution that works absolutely fine.

Euro Car Parts have the most accurate battery finder tool, go to it right here.

Then you can enter either:

1. your number plate
2. your car make and model

Up will pop all the batteries that fit your exact car.

You will notice that all the batteries have similar capacity.

Now you know approximately the capacity (Ah) of your car battery.

The approximation method

If there’s some reason you can’t do that, or perhaps you want a charger for several different cars, here’s the approximation method…

Typically, modern car batteries are around 50Ah capacity.

• Small to medium sized cars may have a capacity between 40-50Ah
• Larger cars can have a capacity around 50-80Ah

So you can reasonably guess that your car battery is within one of these ranges.

Please note, if you want to be absolutely sure of the capacity, you’re best to use the first 2 methods mentioned.

2) The Amps you need your car battery charger to deliver is around 10-20% of the capacity of your battery.

10% is the minimum Amps charging you need.

20% would be ideal as it’ll really fill the battery and provide faster charging (if that’s something that appeals to you).

We wouldn’t recommend going above 30%.

So, let’s take our example earlier.

The Lion 096 battery had 70Ah capacity.

So the minimum car battery charger Amps you need is 70 * 10% = 7 Amps.

Remember that a typical normal sized car has a capacity of around 50Ah.

So for most people with normal sized cars, a charger with 5A charging is enough for you. Since 50Ah * 10% =5 Amps.

Why is car battery charging Amps important?

At Car Battery Geek, we sometimes describe Lead-acid batteries as being capricious.

They like to be treated a certain way, and if they aren’t they’ll punish you.

In this case, if you charge a battery will too low an Amperage, it will never achieve a full charge, no matter how long you charge it for.

Batteries need a certain amount of oomph in the charge you push into them.

It’s been observed over time, that the amount of Amps that provide enough of that oomph is around 10% of the rated capacity of the battery.

Any charging amperage below that, and it won’t fully charge.

What are the effects of undercharging a battery?

Well, batteries have a memory effect. If your charging Amps are too low, maybe the maximum charge your battery can reach is around 80%.

If you consistently only charge it to that level, the battery will treat that 80% charge as its new maximum. So you’ll never reach the full charge that the battery is capable of.

For example, if you charge a 50Ah with only 3A or 4A charge, you’ll never be able to get the 12V battery to full charge.

The effect of this consistent undercharge is that it damages the battery and shortens its lifespan (how long do 12V vehicle batteries last?). It’s even worse in the case of charging Calcium (Silver Calcium or Ca-Ca) batteries – they really don’t like undercharging and can die fast.

How should I choose a car battery charger?

Now that you know how many Amps you need to charge your 12V battery, you may be wondering what other factors are important in choosing a battery charger.

As well as the charging Amps, the charging voltage is important too.

The best modern chargers have several different steps they go through to make sure the battery is charged properly.

An old-fashioned charger from 15-20 years would typically squish the full amount of charge in constantly, but that’s not what a battery needs, if you want it to last.

CTEK, for example, have a 7 to 8-stage charging process that gives a full-throated and speedy charge at time, but also is able to calculate the right time for each battery to taper off the voltage and Amps, to ensure it charges properly. Their best charger is their MXS10 model.

Ideally, you want a desulfator-charger that desulfates the battery while it charges. Why? Because that can extend the battery life by as much as 2 or 3 times. Sulfation is accumulation of lead sulfate on the battery plates. It’s the biggest killer of lead-acid batteries. Luckily, a good quality charger can remove it and prevent it from building up in the first place (and there are a couple of other ways to remove sulfation as well).

One of the best desulfator-chargers is the NOCO Genius 10 charger. It has a long history of not only charging batteries well, but improving their health with its desulfator mode.

CTEK chargers also have the famous CTEK Recond Mode. Like the NOCO chargers, CTEK’s chargers have a great reputation for rescuing failing batteries by removing sulfation. As well as keeping them healthy and ensuring they last longer. Here is which is better out of CTEK or NOCO.

Here are the top car battery chargers in the UK.

If it’s an AGM battery you have, check out the top AGM battery chargers.

What Amp Car Battery Charger Do I Need: Summary

In this article, we answered your question: “What Amp battery charger do I need?”

We described exactly how to find out the right charging Amps for your specific battery.

Basically, it boils down to: find out the capacity of your vehicle battery in Ah. Then take 10% of that capacity. Boom! You have the minimum charging Amps needed to charge that battery.

We described what to do if you don’t how to get the capacity of your battery. And we gave you a rough estimate of the Amperage of charging needed for a medium sized car – normally 5A is enough.

Finally, we looked at the other important aspects of charging, and what you should look for in a 12V battery charger.

Hopefully, you’re now sure how many Amps you should charge the battery with, and you know how to choose the right charger to achieve that.