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What to look for in a car battery charger

Every car workshop needs a good battery charger.

As well as a set of spanners, a jack, screwdrivers, a hammer and penetrating fluid, there’s another piece of equipment without which no workshop – from the home shed to the biggest pro workshop – will ever be complete without. And that’s a good car battery charger.

Now, while we all know that a car’s battery powers its electrical systems (everything from the lights to the ignition and starter motor) what happens when that battery runs out of charge? In normal running, of course, the car’s alternator keeps the battery topped up, but if that system fails or a car has simply been sitting for an extended period, the battery winds up flat and, fundamentally, useless. And that’s when the car becomes useless in sympathy.

That’s where a battery charger comes in. By connecting the charger to the car’s battery (in situ, if necessary) you can return the battery to a fully-charged state where it can once again make a car work.

This works in exactly the same way as plugging your phone in to its charger overnight to recharge its battery. So what are best car battery chargers for your needs?

The fist thing to establish is what voltage your car’s battery operates at. In most cases, that will be 12 volts, but in some trucks can be 24 volts. 

In older cars (including old Holdens and early VWs (to name just two) you could be dealing with a six-volt system. So you either need to buy a charger to suit that voltage or find a charger that can switch between voltages. 

If you don’t need these alternative voltages, a simple, 12V, small battery charger will be cheaper to buy.

The next step is to determine what charge rate you need. A rate of two amps will happily charge a small battery, but somewhere closer to eight amps is better for fast charging a full-sized battery in a few hours. 

Ten amps or more is good for big, deep-cycle and truck batteries. But even a two-amp charger will work on these, it’ll just take longer.

Old fashioned battery chargers were the manually-switched type where you hooked them up, and manually disconnected them to stop them overcharging. 

These days, in better brands and models of charger, there’s computer control of the charging function, so you can leave them hooked up and even switched on. 

Generally, the time taken to charge a battery from flat to full is determined by the amperage.

The really clever ones offer all sorts of overheating and overcharging protection and can virtually be left on the car full-time whenever it’s not actually being driven. Modern calcium battery technology (where the plates have about one per cent calcium to reduce gas production) help in this department, too.

The better chargers will also charge you battery in stages where the charger first gives the battery plenty of amps to return its charge.

Step two involves slowing that charger rate down to protect the battery (just like an EV charge-point slows down for the last 20 per cent or so). 

Most car batteries operates at 12 volts.

And the third stage is to reduce the charging to a small trickle of milli-amps to keep the battery at 100 per cent of its capacity.

Don’t forget about modern, solar-powered chargers, either. These are a great way to keep a battery charged at all times by acting as a trickle charger, and, since it’s sunshine powering them, they’re a zero-emissions solution to battery maintenance. 

And although the solar panel element makes them bulkier, they’re still portable, so they can go camping with you to extend the life of your fridge battery.

CTEK Multi XS 7000 battery charger.

A really good battery charger will often have a function that 'reconditions' the battery by cycling it slightly once it gets to full charge. 

Some also have a 'maintenance' setting where you leave the battery permanently connected to the charger (when you’re not driving the car, of course) and this will keep trickling charge into the battery as well as cycling it slightly. Both CTek and Suaoki are well known brands offering this level of technology.

You’ll pay more for this high-end type of charger, but if it saves you from a dead battery or even having to replace a battery (even one for a small car) it will pay for itself pretty quickly.

David Morley
Contributing Journalist
Morley’s attentions turned to cars and motoring fairly early on in his life. The realisation that the most complex motor vehicle was easier to both understand and control than the...
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