Why is my cars battery draining and ways to prevent it

Your car's battery is essential to your car's operation, but what happens when it goes dead? We take a look at common faults and how to deal with them

Lawrence Minnie

29 Jun 2022 · 08:51Car Ownership

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Drain you

Your car's battery is the main source of power for your car, it powers all the accessories and turns the engine over. There is nothing worse than arriving at your car and hearing the ominous click that comes with a flat battery.

There are a number of reasons why your car's battery might be flat, and we take a look at some of the more regular occurrences and what you can do to remedy the situation.

Bad battery

This is rather self-explanatory, the battery in your car has a finite life span, roughly 2-3 years before degradation sets in and the battery stops holding charge. When this happens the car's battery will discharge in a very short time and you will need to drive it every day to stop it from completely discharging. You will need to buy a new battery as soon as possible to avoid being left high and dry when your engine won't crank over.

Bad alternator

When your car's alternator fails it will not charge the battery sufficiently and the car's engine will actually drain the power from the battery. This does not happen very often but when it does, you will see the battery warning light on your car's dash illuminated, and you will need to have a mechanic take a look at the alternator to have it fixed or replaced.

Vampire accessory

In this case, there will be an accessory that slowly drains power from the battery. This could be a small light, anti-hijack unit, aftermarket accessory or older alarm system. This could also be caused by the vehicle's interior light when a door has not been closed properly or the car radio has been left on. The solution here is to find the cause of the drain and fix it before properly recharging or replacing the battery.

Short circuit

This is the hardest to pinpoint as your vehicle's electrical system is 100's of metres long and has a number of closed and open circuits that could all be responsible. The best solution here is to try and troubleshoot it yourself by checking fuses and relays but should you not find the issue, a visit to an auto electrician may be in order.

Disconnecting the battery when the car is not in use can save you some downtime, but this really needs to be addressed urgently as electrical fires are the number 1 reason that vehicles catch fire at all.

Written by Lawrence Minnie

Lawrence has been involved with motorsports for almost 30 years. Whether it's two wheels or four, if it has an engine, he will try to race it. This love of motor vehicles has led him to ride, drive, film, photograph, and write about his passion. Freelance for a while but now a permanent fixture on the AutoTrader team for over 7 years, Lawrence contributes written, photographic, and video content for AutoTrader and AutoTrader Bikes.Read more