Car battery drain test involves some practical test that you can do before taking it to your garage or mechanic. The most practical way is for you to buy a test light and digital voltmeter which you can use for testing if you have a battery drain or not. Simply put it, don’t do any replacing of the battery if you have not done the car battery drain test because because you are just going to waste your money.

First and foremost is always buy a test light and voltmeter with high impedance. This is not a high sounding technical terms but it only means the tool you will use will not harm the electronic components of your engine. Most computerized engines are very sensitive to voltage fluctuations and if you use a tool that affects their ratings, these engine components like sensors or solenoids can fail.

Next, measure the voltage rating of your battery when the engine is running. If the battery is low, make sure to charge it before doing the car battery test. Now during the test, the battery voltage should read between 13.6 to 14.5 volts or close to this but should not go lower than 13 volts or higher than 15 volts.

If you don’t get these voltages across your battery terminals while the engine is running, do the same test to the alternator. This time, put the positive lead on the output terminal of the alternator and the negative clip on the battery negative or vehicle frame. If you get the same reading, then check the alternator feed supplies if it is getting any voltage. Otherwise, that might be the reason your battery is getting dead if the alternator is not working.

Finally, if you find that the alternator is OK, do a quick battery drain test as shown in this video here. If will show you how to proceed if the battery drain is serious so that you need to see all the electrical components using a wiring diagram. Remember, it is not worth replacing either the battery or alternator until you have checked you electrical system. If you do your car battery drain test this way, you will save money and avoid wasting your time.

Thanks!

Attached is my video on how to check car battery drain quickly: