An engine that's slow to turn over when starting is often a sign of dead battery cells.
So, a test of the resting voltage is just as effective a diagnosis.Ī battery usually won't go bad all at once instead, some of the cells that make up the battery will go dead.
#Digital 12 volt battery meter how to
How to find dead cells in a car batteryįirst things first, knowing a battery cell is dead is of no more use to you than knowing that the battery won't hold a 12.6 volt charge, because you can't fix it. For more on the charging system in your car, see When Good Alternators Go Bad (and Why). A healthy charging system should give a reading of between 13.8V and 14.4V at regular idle speed.Īnywhere outside that range and your car's either under, or over charging – both of which will shorten the battery life and require further investigation. So with the engine running (and being mindful about moving parts) conduct the same battery test as above with your multimeter. Not only that, but while you're driving it also takes over and delivers power to the car's electrical systems. Time to change the battery? Here's how to do it How to check your alternator with a multimeterĪn alternator produces electricity and charges the battery. If it holds a charge when it's not connected to the car – something is draining the battery far faster than the computer memory and digital clock. If the multimeter reads less than 12.6 volts, disconnect the battery and fully charge it using a battery charger. If you suspect this is killing your battery during storage, you might be wise to disconnect the battery or remove it entirely. So, systems such as the clock, computer and alarm use some power. One thing to bear in mind is that all modern cars experience 'parasitic loss', which is when something electrical drains the battery even with the engine turned off. A battery that reads 12.2V is actually only 50% charged, and is classed as discharged below 12V. The resting voltage should ideally be no lower than 12.6V. If you get a reading with a minus in front of it (-12.6 rather than 12.6) you've got the probes the wrong way round! Touch the red probe to the positive (usually red) terminal, and the black probe to the negative (black) terminal. Set the dial to 20, which will allow you to accurately measure between 0-20 Volts. The first test with your multimeter will measure DC voltage, indicated with a solid line and a dashed line above a letter V. Jump starting a battery: the right and wrong ways to do it How to check a car battery with a multimeter Once the battery is exposed, be extremely careful that nothing metal touches the terminals and causes a short, so don't rest wrenches or other tools on top of the battery.
There may also be a red cover over the positive (+) terminal that will lift off or snap open, too. In modern cars, the battery will often have a plastic cover which will unclip, hinge up, or occasionally require removing with a few bolts or screws. Using a multimeter to test a battery is easy. The first thing to do is make sure you can access the battery terminals (the metal connections on the top or front of the battery).īatteries are commonly located in the engine bay to one side of the engine. If the battery is not immediately obvious when you open the hood, consult the owner's manual.
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