How To Test Your Car Battery (Find A Drain)? You need to learn how much current is being pulled from your car battery when it is idle or off. Benefits of this knowledge is figuring out if too much current is being drawn out this way. With stereo systems hooked up or something in the car not working optimally, this is your first step to determining battery drainage risk.
- Get yourself a quality voltmeter; this is your number one tool for the job. Set it to ‘current mode’. Your radio stations will not be reset if you perform the tests without fully disconnecting the battery.
- With the car turned off, hold the negative terminal cable (which will be black) to the negative on the car battery (also black). Hold the metal tip vertical on the node in question.
- Jiggle the bolt back and forth to extricate it slightly up and away from the node; stay safe throughout this process.
- The fact that you have the terminal connected still, as outlined earlier, means the battery will assume the connection is present; no radio station resets.
- The voltmeter will probably show 5-6 milliamps on the display readout. Put the bolt back down once this small current value is detected and move to the next step.
- The 6 milliamps is negligible. You need to see a value of 50 milliamps or thereabouts. Bear in mind that this is ‘milliamps’ not ‘amps’. Anything higher than 50 and that is too much current being drained.
You can figure out if there is a ‘parasite’ drawing from your battery using this technique. It will certainly save you time and trouble in the long run or make the work of a professional battery expert easier where diagnosis is concerned.
- When the car is off, most vehicles have a tendency to draw battery current. This is the ‘parasitic’ behavior being discussed.
- Stereo systems or similar electronics, alarms, and glove box lights inside cars are often to blame for this pattern.
By resolving these issues, even finding out the problem-points on your own using circuit methods, you can keep excessive power from being drawn or drained out of your car battery. If you let this go on, your battery will demand charging more often and for longer time periods. Also, chances of your battery becoming non-functional is slightly increased.