Car battery FAQs - everything you need to know

1 December 2017
, CarsGuide

What is a car battery?

They’re the box of sparks which make your car work, but car batteries are filled with mystery for many people. Actually, they're a fairly basic piece of technology that you’ll probably have to work with at some point.

In car nerd-speak they are a rechargeable 12-volt lead-acid battery made of six cells and are only designed to send a high-output charge to the starter motor to start the car’s engine, after which the alternator recharges the electrical system.

A car battery also provides overflow power when the draw from running multiple electrical features at once, like radio, lights, wipers, and heater in poor weather at night, is high.

Batteries were first fitted in the 1920s in six volt format, before stepping up to today’s 12-volt format in the 1950s with the rise in complexity and performance of the then-current vehicles.

Just like smartphones and high-end electronics, the lithium car battery has now become a far more common fitment in late-model cars thanks to their improved life-cycle, power, compact size, light weight, better environmental efficiency, and cheaper production costs.

How long do batteries last?

Historically, batteries needed electrolyte refills but these days they don’t need to be topped up. Some cars also come with a thermal blanket around their battery to minimise maintenance, and promote longevity.

Batteries are affected most by long periods of inactivity and also extreme cold conditions. This is why most manufacturers make a lot of noise about the Cold Cranking Amps (CCA) of each battery, as a quick reference to work out how much cranking power the battery has, which tells you how well it will start your car depending if it has a large or small engine.

Batteries can be upgraded to take into account aftermarket accessories fitted to cars which draw more current, like spotlights, winches, or even large aftermarket stereos. Serious off-road 4x4s will often run a second battery to handle these accessories. 

While marine and truck batteries used to be the upgrade to handle heavy duty applications, those batteries are huge, expensive and very, very heavy. Today, high-tech aftermarket batteries are very compact, lightweight 'dry-cell' units from companies like Braille, or Odyssey. These units, which can even be mounted lying down, are also extremely expensive at four or five-times the price of a stock lead-acid battery. 

You can also get 'deep-cycle' batteries from companies like Optima, which are designed to handle long periods of inactivity or long periods of cranking. Again, cost is a significant drawback to these batteries.

Batteries are affected most by long periods of inactivity and also extreme cold conditions. Batteries are affected most by long periods of inactivity and also extreme cold conditions.

How to choose a battery for my car

Car battery prices generally range from $75 up to $1500. Cost and cranking amps are only two factors to take into account when working out the best car battery for you – there is no specific best car battery to simply go and buy. 

Most auto parts stores will have a guide to suggest what specific battery your car needs, and then it is simply a job of swapping those batteries over.

Some batteries will have their positive and negative terminals in different positions, and the terminals can range in size from small to large. This is why, for the average vehicle, it is best to go to auto parts store, who will have a specific battery listing for your vehicle.

How do I fix a flat battery?

At some point we will all have to deal with a flat battery, when the car won’t even crank or have any lights on the dash. There are several options to getting your car restarted, depending on how the battery has lost its charge. 

The way most Aussies will be familiar with involves 'jumper leads', which you attach to another car’s battery terminals as well as your own flat battery. You do this by matching positive and negative terminals.

It is important to read your car’s manual as some modern cars need to have the ground strap on the flat car attached to a special fitting in the engine bay. Some cars have special points under the engine bay to attach the jumper leads to, so read the manual to double-check how you should connect the jumper leads.

With the other car running at above idle speed while connected you should be able to start the car with the flat battery. It is important to then drive the car for at least 30 minutes to allow the battery to recharge.

If you have a car that spends a lot of time at home in the garage not driving you can buy what is called a trickle charger. Costing under $300 these units plug into a wall outlet and will gradually recharge or maintain the charge in your car’s battery. Again, you should read the manual to find out if you attach to the battery or an auxiliary point.

Changing a car battery

Installation of a new battery is simple, taking under an hour, and requires only basic hand tools. Car battery replacement can even be done in the carpark of an auto parts store!

1.    Check the manual for the location of your car’s battery. Most are in the engine bay but some are behind seats or in the luggage compartment.
2.    Remove the battery blanket if the vehicle has one.
3.    Most cars will need a spanner or socket to loosen the battery terminals. 
4.    Once the terminals are able to be lifted off, tuck them aside.
5.    You can then undo the battery clamp, or tie-down, and lift the battery out.
6.    The new battery and tie-down can then be fitted, and terminals reconnected.