Suppose you are late for work and need to get going. So, you get in your car and attempt to start it. But unfortunately, the car doesn't seem to start. All you can hear is a small click when starting your car. Not only that but in many cases, you may observe a pair of dimmer than normal headlights when starting your vehicle. This perhaps has something to do with the battery of your car. The car battery may have drained due to unusual circumstances, which is something to worry about. So in motorsparepart, I am going to discuss the causes and prevention method about how to eliminate this issue.


What causes car battery draining when the car engine is off?

Car batteries may drain due to several reasons. In most cases, it is quite hard to determine what the actual problem is. So, what exactly causes a car battery to lose charge? Here are some reasons that should be taken into consideration:

Headlights On
  • Have you left the car headlights on? This is a very common mistake but can cause you heavy damage. If you did leave the car headlights on accidentally at night, there is a very slim chance that you would be able to get your car started in the morning, as it is possible that the battery has drained itself up!
  • There are some features like the clock or radio settings of your car which are operational even when the car is not running. This is quite normal, and the power usage of these utilities is very minimal. But if there is an electrical issue, then your car battery may get drained faster than normal and cause problems.
  • A bad charging problem can cause the car battery to drain drastically. You may be left stranded on a highway if you face problems with battery charging.
  • If your alternator diode has gone bad somehow, then it may cause your car battery to drain quickly. Even when the engine is shut off, the internal circuitry may be taking up juice from the battery. This will eventually end up in battery failure, and you may not be able to get your vehicle started.
  • The battery that has not been replaced in 5 years or more is very likely to give you problems more often.
Battery Faulty

Now that we have discussed the reasons which can cause problems with your car battery, we would like to recommend an easy diagnostic method for convenience. This method has proven to be quite handy when you are facing problems with your car battery:


How to check for a faulty car battery?

Car Battery Testing

Get a multimeter and check your battery. Before starting this process, you may want to turn on your headlights and leave them for about 2 minutes. This gets rid of the excess surface charges and gives you a proper reading.


Now attach the leads of the multimeter to your battery terminals and check. If the voltage if above 12.6 volts, then your car battery is fine.

You need to do another test alongside this one. Keep the voltmeter leads attached to your battery and start the car. If the voltage rises to about 14.4 volts or something similar, then your battery checks out, and you can assume that it won't stop working in the middle of a highway!

How to prevent car battery draining

Apart from the diagnostics, you should keep in mind the things that you should and should not do. For instance, it is not wise to keep the car headlights on without any reason. Keep the headlights of your car turned off when they are not in use.


Choosing a good battery for your car will always save your time and efforts in the long run. It is wise to get a battery that is not more than 6 months old. Also, it is recommended that you buy Absorbed Glass Mat or AGM batteries for better performance. AGM batteries are much tougher and more consistent than the regular Lead-Acid batteries. Buying the right battery will determine the overall performance of the vehicle. 


A car battery that has a higher CCA (Cold Cranking Amps) rating is much more convenient for use. CCA is the measure of a battery's ability to start the engine of a car in cold climates. CCA rating is measured in the number of Amps at 12-volt battery can deliver at 0- degrees Fahrenheit for 30 seconds while maintaining a voltage of 7.2 volts. You must consider the CCA rating if you live in a cold climate.

Car Battery Draining And Changing It

A battery that is more than 5 years old should be changed for better performance. Most batteries run smoothly for 4 years and then start to wear out. If you want smooth and optimal performance, this is something you should consider doing.


A dead car battery can be annoying sometimes. So, it is better to take preventative measures so that your car battery performs smoothly and does not end up drained out completely. It is recommended to hook up with mechanic ones now and then and get your car checked out.


About the author


Hello, My name is Andrew David, a passionate car lover, and enthusiast.
I am not so called expert but love to share my experiences and knowledge regarding the car and motor parts for all vehicles.