As you drive along the belt driven alternator takes over the role of delivering power to the car's electrical systems and also recharges the battery. The alternator's job is to produce electricity and charge the battery.
#Cen tech 7 function digital multimeter to check car battery how to
Time to change the battery? Here's how to do it How to check the alternator with multimeter If the battery 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 you get less than 12.6 volts, disconnect the battery and fully charge it with a battery charger. If you suspect this is killing your battery during storage, you can either disconnect the battery, or remove the battery from the car entirely. Even with all the lights and engine turned off, the digital clock, computer, and several other systems use some power. One thing to bear in mind is that all modern cars experience 'parasitic loss' where something electrical drains the battery even with the engine turned off. Bear in mind that when a battery goes down to 12.2V it's actually only 50% charged, and below 12V it's classed as discharged! If you're getting a reading with a minus in front of it (-12.6 rather than 12.6) you've got the probes the wrong way round!Īs we've discussed the resting voltage should ideally be no lower than 12.6V. The terminals will be marked + and -, and often color coded red for positive and black for negative. Touch the red probe to the positive terminal, and the black probe to the negative 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 car battery with multimeter There may also be a red cover over the positive (+) terminal that will lift off or snap open too. Once the battery is exposed be extremely careful that nothing metal touches the terminals and causes a short, so don't set wrenches or other tools on top of the battery. 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. 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. Testing a battery with a multimeter is a simple process.