Every vehicle's reliability – even EV’s - depends on the 12V battery, a faulty battery creates a faulty vehicle, but a battery’s performance isn't just down to the condition on the inside of the battery. Many outside factors can affect battery health, leading to more roadside breakdowns. .

When a battery fault occurs, the first assumption is the battery is either flat or faulty. This could be the case, but you should also ask yourself, is there another reason why the battery has failed?

Below are the five most common problems that contribute to battery discharge which will eventually lead to battery faults and replacement.

1, Physical Battery Condition

Even though the battery is under the bonnet or elsewhere inside the vehicle and away from harsh outdoor conditions doesn’t mean that it is fully protected. Most often you will find that the terminals on the battery will start corroding.  This is due to a chemical reaction that occurs between the terminals and the sulphuric acid present in the battery.

If left unchecked, the corrosion can span across both terminals, causing a constant drain on the battery even when the vehicle is off and stationary. The longer the battery is left in poor condition, the worse the battery’s health becomes ending in battery failure and possible replacement required.It is a good idea to check the condition of the terminals periodically – for example when topping up oil or screenwash.

2, Faulty and Damaged Door Switches/Sensors

You’ll notice that when you open your vehicles door the interior lights will activate. This is triggered by a switch that is housed in the door that can detect when doors are open/closed. When you first open the door, the lights aren't the only thing that awakens. Most modern vehicles infotainment systems will also activate and get ready before you start the vehicle.

If one of your door switches is faulty and malfunctioning, it may lead the vehicle to believe that you have the door open and keep all the vehicle's systems awake and functioning, placing a large drain on the battery. An easy to spot give away for this would be to see if the interior lights are on when the vehicle is not in use and locked.

3, Faulty Starter Motor

A starter motor’s job is to receive a high current from the 12V battery and use that to crank/start the vehicles engine. Usually, the starter motor can do this without a fault however if it is pulling more current than is required this can place an unnecessary drain on the battery. If the starter motor is faulty then every time you start the vehicle, either when first entering the vehicle or when auto stop/start engages, the starter motor will be placing a heavy drain on the battery. Your local car workshop should be able to test your whole starting system when they test your battery.

4, Improperly Installed Aftermarket Electronics

It is very common for people to install aftermarket electronics to their vehicles. These devices can range from anti-theft devices to dashcams all the way to new head units and loud, bassy speakers. It is essential when installing these devices that all wire connections are secured in properly and there are no loose connections, to avoid causing a parasitic drain. If you are trying to diagnose where a drain is coming from it can be hard to find a fault with aftermarket solutions installed.

5, Keyless Entry Systems

Keyless entry systems have made locking/unlocking and starting the vehicle as easy as hitting a button. This works due to your key transmitting a unique low-frequency signal that communicates with the vehicle. When the vehicle detects the key is within range the vehicles systems will activate waiting for you to start the vehicle. If you leave the keys near the vehicle when locked and not in use (like by the front door for example) the vehicles systems will always stay active, placing a drain on the battery. Aim to store the keys as far away from the vehicle as you realistically can or use a signal blocking ‘pouch’.