Why Is My Car’s Battery Always Draining?

A question that our customers often ask whenever they come to us for car servicing in Bromley is, “why does my car battery keep dying?” Well, we have got you covered. In this guide, we will explain all the reasons you need to know. So, keep reading until the end.

At Bromley Vehicle Test Centre, we specialise in diagnosing and fixing battery issues, ensuring your car stays powered and reliable. With over four decades of experience, our expert team offers a full range of services to keep your vehicle in top condition.

Need help with your car battery or any other vehicle issues? Call us today on 020 8460 6666 or email us at  for more information.

What Causes Car Battery To Drain?

Let’s begin with the answer to why the car battery keeps dying. Here are some reasons below:

1. Leaving The Lights On

One of the simplest reasons a car battery drains fast is leaving the headlights or interior lights on. Many cars have automatic shut-off features, but if yours does not, the lights will stay on and drain the battery until it’s completely empty. Even a small light, like the trunk or glove box light, can lead to battery discharge over time.

2. Parasitic Drain From Electrical Components

Another reason why the car battery keeps draining is due to a parasitic draw. A parasitic drain occurs when electrical components continue to use power, even when the car is turned off. The clock, alarm system, and radio may continue drawing small amounts of power, but things like door lights or faulty relays can cause a significant car battery drain. Over time, this adds up, leading to a battery that won’t start your car. A malfunctioning electrical system can exacerbate the issue, making it harder to pinpoint the cause.

3. A Faulty Alternator

Your alternator is responsible for recharging the battery while the car is running. If the alternator is not charging properly, it will not provide the necessary voltage to keep the battery charged, leading to a situation where the car battery drains fast even when driving. Symptoms of a bad alternator include dimming headlights or difficulty starting the car, even after driving for a while. If the alternator is not charging effectively, it may be time for a car battery drain repair.

4. Corroded Or Loose Battery Connections

Corroded or loose battery terminals are another common cause of car batteries draining overnight. When the connections between the battery and the car’s electrical system become loose or corroded, they hinder the flow of electricity. This can prevent the battery from being charged properly while the engine runs. If you notice white or greenish powder around the battery terminals, it’s a sign of battery terminal corrosion, and you’ll need to clean and tighten the connections.

5. Short Drives That Don’t Recharge The Battery Properly

Frequent short journeys might lead to a car battery draining fast over time. When you start the car, the alternator needs time to recharge the battery. If you’re taking multiple short trips, the alternator may not have enough time to recharge the battery properly. A partially charged battery will eventually run out of power, causing it to die. If your battery keeps draining, even after driving, you might need a longer trip to allow the alternator to recharge fully.

6. Extreme Temperatures

Cold temperatures can cause battery discharge by freezing the fluid inside, which reduces the battery’s ability to produce the necessary charge. On the other hand, hot weather can evaporate the fluid and damage the battery’s internal structure. Extreme temperatures can cause a car battery to drain fast and shorten its lifespan, whether it’s cold or sweltering heat.

7. Leaving The Car Sitting For Too Long

If your car isn’t being used for an extended period, the car battery can drain as its electrical components slowly draw power from it, even if the engine is off. To prevent this, try starting your car every few days, or take it for a short drive at least once a week. If the car sits idle for weeks, you may find the battery drained when you try to start it again. This is especially problematic if the battery is old or already weakened.

8. An Old Or Worn-Out Battery

An ageing battery is one of the top reasons car batteries keep draining. Over time, all batteries lose their ability to hold a charge, and a worn-out battery may not be able to keep your car running smoothly. If your battery is over 3-5 years old, it might be time to replace it. An old battery is more likely to drain fast and is less efficient at holding a charge, especially if it’s regularly exposed to extreme temperatures or frequent short trips.

9. Malfunctioning Fuse Or Relay

Sometimes, a malfunctioning electrical system in your car, such as a faulty fuse or relay, can cause the battery to drain unexpectedly. Relays control the electrical circuits in your vehicle, and if one fails, it may leave certain components powered on when they shouldn’t be. This issue is harder to detect without the help of a professional mechanic, but it can be the source of an ongoing car battery drain problem.

10. Using Aftermarket Electronics Or Accessories

Using aftermarket electronics such as high-powered stereo systems, GPS units, or dash cams can create an accessory power drain, even when your car is turned off. These devices can continue to draw power, leading to a slow but steady battery drain. If you use electronics like these regularly, disconnect them when not in use. Sometimes, the wiring may need to be adjusted to prevent continuous battery draw.

What Are The Solutions To Prevent Car Battery From Draining?

To stop the car battery from draining, follow these helpful car battery drain solutions:

1. Turn off all lights: Double-check that all, including the interior and trunk, are turned off. If available, ensure your car’s auto-shutoff feature is working.
2. Check for parasitic drain: Inspect any electrical components, such as faulty relays or lights, that might continue drawing power when the engine is off.
3. Inspect alternator performance: Ensure the alternator is charging If it’s malfunctioning, a car battery drain repair may be necessary.
4. Maintain battery connections: Clean battery terminal corrosion and ensure all connections are secure.
5. Avoid frequent short trips. Take longer trips to give your alternator enough time to fully recharge the battery.
6. Take help from professionals: If you can’t find the cause of the drain or fix the issue yourself, it’s by a professional mechanic. They can help pinpoint the problem and offer expert solutions to stop car batteries from draining quickly.

Addressing these issues can prevent car batteries from draining fast and extend your battery’s lifespan.

Bromley Vehicle Test Centre: Your Solution To Battery Drain Issues

At Bromley Vehicle Test Centre, we understand how frustrating a constantly draining car battery can be. With over four decades of experience in car servicing and repairs, our expert team can diagnose the root causes of your battery discharge, from faulty alternators to electrical system malfunctions.

Whether it’s corroded battery terminals or parasitic drains from your vehicle’s accessories, we provide reliable solutions to ensure your car stays powered. We offer comprehensive battery checks and repairs, giving you peace of mind that your vehicle will run smoothly and efficiently.

If your car battery keeps draining, don’t wait for the problem to worsen—contact us today! Call us on 020 8460 6666 or email us at to schedule an appointment.