Ah, the dreaded feeling that most of us have experienced when we go to turn on our car … and nothing happens. We turn the key again (or press the stop-start button) and silence. Yup, it’s a flat battery – and it usually happens when you need to make an urgent trip. 

A flat car battery is annoying and today’s vehicles are packed with power-hungry technology than can drain it.

But Swedish company CTEK, the leading global brand of in-vehicle charging solutions, has the top 10 things that could be draining and/or affecting the performance of your vehicle battery. 

1. Too many short trips

Nipping out on lots of short journeys, particularly in urban areas, drains the battery, as it takes 150-350A of battery power just to start the car, and on short trips, the alternator won’t have the time or capability to replace this charge.  

2. Cold weather

A battery can lose as much as 35 percent in performance when temperatures hit freezing, and up to 50 percent if temperatures sink below that. Drivers should look out for any signs of change – like the way the car starts, or the operation of the electrical system in general - as these can be indications of a weak battery.

3. Keys too close to your car

Leaving your car key in your car overnight or even on a hook near the car is not recommended. If the fob is too close to your car, it can continue to communicate with it, which could needlessly drain the battery. 

4. Self discharge

Your standard lead-acid battery will naturally drain at 0.1V per month – even sitting on a shelf. That may not sound a lot, but if we consider that a fully charged battery is at 12.72V and a chemically discharged battery, at which point you’d struggle to start the car, is at 11.8V, in just eight months of non-use, the battery could appear flat. That is without considering any additional drains that may also impact battery life, too.

5. Drawing power when parked

Even while your car is off, your battery provides power to things like the clock, the radio, and the alarm system, although these things shouldn't have a major impact on your battery. With modern vehicles, though, you’ll also find that engine cooling fans and other systems will keep running after the ignition is turned off to, for example, quickly cool down the engine and prevent damage.

The vehicle may run its own network with communication to the manufacturer servers via the TCU (Telematics Control Unit) – over-the-air updates that are sent out on a regular basis usually impact the drivetrain and infotainment system. The ability to remotely turn on lights, heater, etc, from your phone via an app, can also go through this network.

6. Doors and boot open

Every time you open the doors or boot to get something out, your car springs into life and the interior and door lights will drain the battery. As an example, unlocking your vehicle, popping the boot or tailgate, and locking it again can draw around 50A from the battery. It doesn’t seem a lot, but regularly doing this can have an impact on battery voltage, especially as all the vehicle’s systems become active for the short time that the car is opened up.

7. Parasitic drain

Parasitic battery drain is something that constantly drains your battery. This could be a headlight/dome-light switch, alternator, or any other electrical gremlins. You can help avoid parasitic drains by turning off every light and making sure your boot, glove box, and doors are fully closed and locked before leaving the car. 

8. Alternator fault

Your car relies on your battery when you fire up the engine. But when your vehicle is running, your battery relies on the alternator to help it stay charged. If your alternator isn't working correctly, it won’t charge your battery properly, which can make it hard to start your car, even if you were just driving!

9. Sulphation

If your battery falls below 12.4V, a chemical reaction called sulphation will start to happen. This is where lead sulphate crystals start to build up on the battery plates, degrading the battery, reducing battery capacity and cranking potential. Your vehicle will easily start if the battery is at 12.4V but beware, your battery is already dying.

10. Time to replace

Nothing lasts forever, including your car's battery. In many cases, it depends on where you live, how you drive, and how you look after your battery – although did you know that over 87 percent of batteries returned under warranty are not faulty, they are suffering from sulphation. 

Extreme temperatures, frequent short trips, and general everyday use could shorten the life of your battery to as little as two to three years if you don’t look after your battery.