How long does a car battery last?

Depending on the type of battery installed and how the vehicle is used, battery warranties generally vary from 6 months to 3 years. However, the length of a warranty period is no guarantee that any particular battery will outlast its warranty period.

Nonetheless, lead-acid batteries usually last for an average of about 42 months. However, this period can be somewhat extended, or greatly reduced by many things, including one or more of the following:

• Using an unsuitable battery for a particular application.
• The condition of the vehicle’s charging system.
• Vehicle use, such as frequent short trips that do not allow the battery to achieve or maintain a full charge.
• Extreme hot and/or cold temperatures.
• Excessive discharges, such as forgetting to switch off the headlights. In such cases, a lead-acid battery might suffer fatal damage.
• Excessive sulphating of the plates that result from never allowing the battery to reach a full charge.
• Prolonged parasitic power draws resulting from faults in wiring or improper fitting of aftermarket accessories such as audio systems or auxiliary driving lights.

There are many other possible reasons why a car battery might fail prematurely. However, regular servicing and proper maintenance of the vehicle, and the battery will largely prevent premature battery failures. Moreover, batteries in well-maintained vehicles often outlast their warranty periods by wide margins.

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How Do I Know When To Replace My Car Battery?

Common symptoms of old, defective, or damaged batteries are much the same across all vehicle types, and these could include one or more of the following:

• The cranking, or engine turning speed has reduced noticeably when you are starting the car.
• The battery may not crank the engine when it is cold but cranks the engine fine in hot weather, or when the engine is hot.
• The battery runs down overnight, or even if the vehicle is parked for a few hours.
• The battery’s casing is distorted, or the casing seems to “bulge” out on one or more sides.
• You get the smell of rotten eggs or battery acid when the engine runs. This is often accompanied by a build-up of acid on the positive terminal.
• The battery warning light is on. The light could be on because the alternator is not working, or because the battery has failed. However, a battery warning light can also be caused by other problems in the charging system.
• When you experience strange behaviour from the anti-theft/security system, and/or the central locking system.
• When you notice that power windows do not open or close as quickly as before.

We also re-iterate that many charging system faults mimic the effects of a defective or flat battery and encourage motorists to find a professional mechanic to assist them with diagnosing and fixing the root cause(s) of the problem.

How To Replace a Car Battery

It is certainly possible to do a car battery replacement on a DIY basis. You could also call for roadside assistance when you get stuck on the road, but a DIY car battery replacement is not really a recommended procedure. Mistakes can cause serious short circuits, and/or the vehicle could lose vital computer programming from one or more control modules.

Some control modules on modern vehicles are always supplied with battery power even when the vehicle is switched off. One such module, the Keep Alive Memory, contains information on the idling speed, basic ignition timing settings, and control parameters for the electronic throttle control system- amongst other things.

Thus, when you remove battery power from the Keep Alive Memory by disconnecting the battery, the information it contains could be lost or corrupted. The only way to repair corrupted programming is to have the vehicle partly or completely reprogrammed.

Losing programming can be prevented by installing a temporary power supply known as a “Memory Saver” before you disconnect the battery. In practice though, memory savers are not created equal, and you might still experience software issues after the car battery replacement.

What To Do if Your Battery Is Old

There is one other problem to consider, which is the fact a car battery’s performance decreases as the battery ages. To compensate for this, most alternators can increase or decrease charging currents to suit the battery’s capacity or condition.

This is a very useful feature, but it does require that the new battery be integrated into the charging system after the battery replacement. This is called a Battery Reset and if this is not done, the alternator and power demand module will not recognise the replacement battery. Therefore, the alternator might overcharge or undercharge the new battery, which typically leads to the premature failure of the replacement battery.

Battery reset procedures are performed with high-end diagnostic equipment, and sometimes with equipment that is specific to a particular vehicle make or model. Buying an expensive scan tool to save a few dollars on labour charges for a battery replacement just does not make any kind of sense. Instead, it makes sense to engage a professional mechanic with the correct equipment, skills, and knowledge to replace the battery in your vehicle.

How To Disconnect/Connect a Car Battery

There are not many reasons why the average car owner would want to disconnect a car battery, except to replace a battery. Nonetheless, the internet abounds with the so-called “advice” to disconnect both battery terminals to “fix” trouble codes.

This is exceedingly bad advice because the only thing this does is to erase the vehicle’s fault memory. When you switch the ignition on again, the onboard diagnostic system will detect the same faults, and the trouble codes will return.

In rare cases, some vehicle manufacturers might recommend that the battery be disconnected for specific diagnostic purposes. However, this requirement usually depends on one or more fault codes or fault conditions not being present.

The relevant service information will tell you if the positive terminal or the negative terminal must be removed first, and which terminal must be re-connected first. Therefore, we do not recommend that you disconnect battery terminals under any circumstances unless you have access to all relevant service and/or repair information.

If you are in any doubt about whether you should disconnect battery cables, do not disconnect them. Instead find a professional mechanic that can advise and assist you with diagnosing and fixing problems you may have with your vehicle.

Head Into Repco for Your Replacement Car Battery

If you’re looking for a replacement battery for your car, truck, or even your lawn mower, the Repco battery range has you covered. Head into your nearest store and ask our friendly staff about the right battery for your vehicle or use our online Rego Check to get the right fit.