How to prevent car battery draining

Common causes of car battery draining

There are many factors that can cause your car battery to drain, some of which you have control over, and some you don’t. Here’s a round-up of the most common causes:

• Leaving lights on

  Forgetting to switch your lights off is a sure-fire way to sap the energy from your battery.

  The issue isn’t as bad if you’re driving, as the alternator will be recharging the battery as you go. However, it’s a different story when the engine is off, because the lights will be getting their power directly from the battery, so they’ll eventually drain it completely.

  How long this takes will depend on its age, voltage, and capacity; it could be anything from a few hours to a few days. Either way, it’s a good idea to double-check all lights are off before you leave your car.

• Parasitic draws

  Certain electrical systems, components, and functions in your car – such as the keyless lock, alarm, radio presets and clock – always stay running in the background, even when your engine is off.

  This uses a tiny amount of power, which has a negligible effect on the battery. Parasitic draw is when this normal electrical usage becomes much higher than it should be. This can be down to something as simple as not closing the boot, glove box or doors properly, or a more serious issue such as faulty parts or wiring, short circuits, or stuck relays.

  So, take this as your reminder to double-check the things within your control.

• Extreme weather conditions

  Car batteries don’t cope well with extreme temperatures at either end of the scale. Cold weather slows down the chemical reactions inside the battery, which makes starting the engine harder.

  Lower temperatures can also cause engine oil to thicken, which puts even more strain on the battery. Overall, battery demand tends to be greater in the winter, as you’ll be using your heater, windscreen wipers, and headlights more often.

  Hot weather, on the other hand, speeds up those chemical reactions, which causes the battery’s essential fluids to evaporate and its internal parts to corrode. This can reduce the battery's voltage, meaning it can’t hold a charge as well as it should.

  Leaving your car open to extreme conditions– whether hot or cold – can hasten battery drain. Therefore, it’s a good idea to protect your car from harsh weather whenever you can.

• Short trips

  Starting up your car uses a lot of battery power – not just for the engine, but for all the other electrical systems that spring into life as you take your seat. Once you start driving, the heavy lifting is done by the alternator, which generates power and transfers it to the battery.

  However, if you’re only taking a short journey, the alternator won’t have the time it needs to fully recharge the battery. Regularly taking short trips is a common cause of car battery draining, as every time you drive, you’ll be using up power without replenishing it. If the battery is never fully charged, this will reduce its life - and eventually lead to it draining completely.

  If you tend to stick to very short journeys, taking a longer drive now and then can help to preserve your battery life.

• Old battery age

  Car batteries aren’t made to last forever. In fact, the average lifespan is around four to five years (less in some cases). Things that affect older batteries include chemical breakdown, sulphate build-up, and fluid evaporation.

  If you’ve noticed that your battery isn’t keeping its charge for as long as it used to, and your battery is over three years old, it’s possible that it’s past its best, so it’s time to get a new one.

Tips to prevent battery drain

There are a few things you can do to prevent car battery drain.

• Regularly test the battery

  You can do this yourself or take it to a garage and ask a professional to do it for you. Either way, the battery should be checked every six months to make sure it is housed securely, has no cracks or bulges, and is holding its charge correctly.

• Clean battery terminals

  Battery terminals can corrode - and get clogged up with dirt and grease. Keeping them clean will go a long way towards improving your battery’s lifespan. You can do this yourself with some cotton buds and a mixture of sodium bicarbonate and water.

• Drive regularly

  Try to drive your car every few days, as this will help to keep the battery charged.

• Avoid frequent short trips

  If you regularly take quick drives (for example, the daily school run), try to intersperse these with longer journeys to give the alternator a chance to fully recharge the battery.

• Use a trickle charger for long-term parking

  If you rarely use your car, or are going to be away for a long time, it’s worth getting a trickle charger. This handy gadget replenishes your battery with the same amount of power it discharges, ensuring it doesn’t drain while your car isn’t being used.

• Switch off lights and electronics

  Make sure you turn all the lights off when you leave your car - and unplug electronic devices such as phone chargers, USB devices, and dashcams.

• Limit electronic accessory use

  Wait until the engine is going before turning on the air conditioning and heated seats, as these can quickly drain the battery.

• Park protectively

  When necessary, find parking spaces that provide cover and protection from extreme temperatures.

How to test and maintain your car battery

It’s easy to test your car battery's health at home using a multimeter. Just follow our step-by-step guide:

• Prepare your car: Turn off the engine and all electrical accessories (lights, radio, etc.), leave it to sit for around an hour, then open the bonnet.

• Set your multimeter: Make sure it's set to measure DC voltage. 23

• Connect the multimeter: Attach the multimeter to the battery. The red probe connects to the positive terminal and the black probe to the negative terminal.

• Check the voltage: The multimeter should read between 12.4 and 12.7 volts. A reading below 12.2 volts means your battery has a low charge.

Regular maintenance can help to prolong your battery’s life and prevent drain. Your routine should include checking for corrosion and other visible damage, making sure the connections are secure, and frequent battery voltage tests.

When to replace your car battery

With the average car battery lasting just four to five years, there will come a time when you’ll have to get a new one. If the tips in this guide don’t make a difference to your car battery’s draining, it’s probably nearing the end of its life.

If the physical damage to your battery is significant (e.g. if the battery case is swollen and cracked), that’s another sign it needs replacing.

It’s important to replace a failing battery as soon as you notice the signs, as putting it off could be dangerous and cause further damage to your car.

If your battery dies while you’re on the road, you could end up broken down and stranded at best, and in an accident at worst. A weak battery can also have a negative effect on your electrical systems, which could lead to you having to shell out for expensive repairs.

When buying a new battery, you need to select the right type for your car, such as lithium-ion or AGM. If you’re unsure about your car’s battery type, you can find this information in your owner’s manual. You also need to make sure it’s the right size and shape.

Buying from a recognised brand is advisable, as is choosing a battery with a warranty. With all this to think about, it’s a good idea to go to your local garage when you need your battery replacing - and let a professional mechanic do the work.