How to select the right car battery for your vehicle

How Long Does a Car Battery Last?

Most batteries on modern cars will last around three to five years on average, with older batteries sometimes lasting one to two. Keeping your battery well-maintained and avoiding too many short trips or lengthy periods without driving can help to make your battery last longer.

How Do I Know If My Battery Is Dying?

Common symptoms of a dying battery can be dimming lights and trouble starting, but there are certain things you can look out for that might pre-empt this.

Cracked Battery Case

A cracked battery case can cause the acid to leak out, which can be incredibly hazardous to the vehicle and to you. It is possible to have a crack battery case repaired with certain epoxies, but generally replacing the whole battery is the best option.

Bulging Battery

If your battery is bulging, this is usually a sign of freezing or boiling of the electrolyte, which can cause catastrophic failure if left unchecked. Other causes of bulging in a battery are damage to the battery case, manufacturing problems, and short circuiting between the plates.

Loose Battery Terminals

Loose terminals can cause flickering of headlights and loss of function to electronics in your car due to electrical charge being interrupted as the loose terminals move about while you drive. This can be a fairly simple fix if the terminals just need tightening, but if excessive corrosion is to blame, you might need to replace your battery.

Finding the Right Battery Size

Different cars require different sized batteries based on their engine and battery compartment size, as well as how much you need to power in the car with the battery. You also need the battery to be physically compatible with your vehicle, meaning the dimensions and location of the terminals on the battery need to fit correctly.

Having a battery of the wrong size in your vehicle will cause it to run inefficiently and can even damage it in the long run, so it’s an important aspect of selecting a battery.

How To Find the Correct Sized Car Battery

The Battery Council International has created a specific BCI group size that gives drivers a helpful guide to which battery size they need for their vehicle. Finding this is usually fair simple, as the battery group size will be located on the label on your battery.

You can also use Repco’s Rego Search to find out the proper battery size for your car, as well as Century’s Battery Finder.

Below is a list of information regarding battery group sizes:

Battery Age Codes

If you don’t have the receipt from the original purchase of your battery, you can use the age code located on your battery to figure out the manufacture date. Battery age codes are formatted differently depending on the manufacturer, so check the owner’s manual for how to read yours specifically.

As an example, if you’ve got an Australian Century Yuasa battery, you will see something like this displayed on your battery:

For this age code, the information reads as follows:

• First Digit = Shift (D = Day, A = Afternoon, N = Night)
• Second Digit = Day of Month
• Third Digit = Month A to M (January to December)
• Fourth Digit = Year A to K (A = 2007, B=2008 etc)

Another common format is to have a date code that is simply two digits, with the first being the a letter and the second a number.

The letter shown represents the month, with A being January, B February, up to L for December. Sometimes, manufacturers will skip the letter ‘I’ for September and make it a J instead, so it isn’t confused with the number 1.

The number represents the year, from 0-10, but note that there can be overlap (a 2011 battery and a 2021 will have the same code of 1) because manufacturers generally expect a battery to only last 3-5 years.

From this example, a battery with the code D7 would be a code for April 2007, which could also be represented as 7D.

Minimum Cold Cranking Amps (CCA)

Apart from size, the other major factor to consider when replacing a battery is the minimum Cold Cranking Amps.

Different vehicles will come with different power requirements for starting the engine, with starts in cold weather being the most important. This is because colder temperatures can slow down the chemical reactions that occur in the battery, which can cause you to get lower electrical current flowing and therefore, less power.

The CCA of your battery needs to meet the minimum rating that is recommended by your manufacturer in order to function properly, with smaller cars wanting a CCA of around 150 and high-performance vehicles wanting something close to 500.

Installing a battery with more than the recommended CCA rating is often encouraged but you never want to get a battery with a lower CCA. If you live in a particularly cold area, CCA becomes especially important.

The best ways to find out your recommended CCA are:

• Look at your owner’s manual.
• Check the label of the battery in your vehicle.
• Look online for the specifications laid out by your manufacturer.

What Is Battery Reserve Capacity?

The reserve capacity (RC) gives an indication of how many minutes of power a battery has in reserve to power accessories and lights in your car when the engine is switched off. If the alternator fails for some reason, this reserve power will also help to keep the car running.  

You can find out the reserve capacity of your battery by checking your vehicle’s owner’s manual or checking the battery label. This value will usually be given in minutes, indicating how many minutes the battery can stay above the minimum voltage required to power your vehicle without the alternator running; for instance, 130 RC would mean 130 minutes of running time.

Figuring Out Which Type of Battery You Need

There are a few main types of batteries that you’ll be looking at for your vehicle.

Flooded Lead-Acid Batteries

Sometimes called ‘wet cell batteries’, these batteries are the most common on the road and use a system of electrodes and plates that are submerged in a liquid electrolyte solution.

These batteries generally have shorter warranties and less CCA than their sealed counterparts and require maintenance in the form of distilled water to help replenish the lost electrolyte that can be released through vents in the cell.

You can also get an Enhanced Flooded Battery (EFB) that acts as an upgrade for flooded lead-acid batteries, with higher durability and improved charge acceptance, often giving double the amount of vehicle starts of a standard wet cell battery.

These act as a cheaper alternative to an AGM battery.

Absorbed Glass Matte Batteries

AGM batteries are the latest form of lead-acid battery and have a lot of benefits. They get their name from the glass matte that is used to suspend the electrolyte inside the battery, which means that it can’t spill. This is further helped by separators that absorb and hold acid to prevent spillage.

The tightly compressed plates in the battery also mean that they are more vibration and impact resistant.

Gel Batteries

While AGM and gel batteries are similar, a gel deep cycle batteries use a gel paste to suspend the electrolyte in the battery case, which makes them spill-proof like an AGM, but the gel inside is more fragile and can be burned if the amperage is too high. They are also generally more costly than AGM batteries.

Stop-Start Batteries

If you have a vehicle with a stop-start or hybrid system, then you’ll want to get a stop-start battery that takes advantage of the fuel saving and emission reducing features of the vehicle. The rapid recharge and superior cycling of these batteries also allows you to run electronics while the engine is off.

Which Type of Car Battery Is Best?

Both AGM and gel batteries are essentially maintenance-free, as they don’t use liquid acid that needs to be topped up and combined with faster charging and higher resistance to impacts, they are generally more desirable than wet cell variants.

It should be noted that gel batteries are more fragile than AGM and lead-acid batteries, which can make them a less suitable choice for general car and truck use, and are better as deep cycle batteries.

In terms of AGM batteries, it's possible to upgrade from a flooded lead-acid battery when replacing your battery, but if your vehicle comes with an AGM battery, you should replace it with an AGM, as wet cell batteries are more likely to overheat, especially in tight spaces with less ventilation, and therefore can't match AGMs one-to-one.

AGM batteries are especially desirable if you live in extreme climates, as they are much better at handling extreme heat and cold than flooded lead-acid batteries.

Century Batteries at Repco

Partnering with Century Batteries, Repco has a wide range of batteries for your car, motorcycle, and even for lawn mowers and boats. If you need a battery replacement, head into your nearest Repco store or shop online and use our Rego Search to get the right fit for your vehicle.