How To Test Car Battery With Multimeter? Batteries, like all mechanical components, can go bad. This is exactly why they need to be tested every now and again to see if they are doing alright. A multimeter (aka voltmeter) is the tool for such a task where car batteries are concerned.
- Symptoms of a bad battery or alternator: the engine may be cranking slowly or not at all, the battery indicator light is lit on the dash, clicking during engine turn-ons but the engine refuses to start, the battery seems or is dead, the interior lights/headlights show alternating dimness.
- In this guide, we are not focusing on alternators but car batteries. Most cars use the battery light indicator behind the steering wheel to show voltage presence in the car battery.
- When you start the car and the battery light remains aglow, something is wrong. It should blink out as soon as the engine roars to life.
- Start the test by turning your car’s headlights on; leave them so for a couple of minutes. Batteries accumulate surface charge and thanks to this decision, you can get rid of the issue as you move to the next step.
- Meanwhile do not stand there wasting time. Turn on the voltmeter and set it to over 15 volts; go for 20 volts, for instance.
- Shut the lights off after the two minutes are up, and head to the battery. The positive lead is red and the grounding node is represented by the negative lead, which is black.
- Use the terminals on the voltmeter to connect red to red and black to black. The display readout will certainly change. If you see a voltage measure of approximately 12.6 volts, all is well with the basic voltage capacity of the battery.
- While the voltage value may be proper, the battery does not necessarily have to be. It may hold the charge but lack the cold cranking amps (CCA; i.e., how many amps a battery can deliver at 0 degrees Fahrenheit for 30 seconds while not dropping below 7.2 volts) required to start the car. This is exactly what you are testing to see if it works.
- When you start the car and the voltmeter’s readout changes you will see that the value drops and then spikes; to 10 volts and then to 14, for example. The latter is due to the alternator charging the battery from within. If the voltage stays at 10 or below, your battery has a problem. Below 5 and that is a serious debilitation.
- While you are at it, make sure the nodes on the battery (red and black) are not corroded with rust or dust. Some sandpaper (rust removal) and WD40 (rust prevention) will resolve this matter right away. Safety is crucial; use goggles and gloves. The corrosion lives up to its name and can hurt your hands or eyes. ‘
- If your battery is the maintenance-free type, all good. If yours needs water, it will have vent caps on top. Fill it just so with bottled water; you do not want unwanted minerals entering a lead acid battery.
Batteries generally last around four years; which is often what their warranty certificates declare. But only 30% of batteries sold on the market today reach that vaunted lifespan. Some even work like a charm after six years; depends on the brand and how well you have maintained it over the years. You can have your battery tested free at major parts stores; they are thorough and have better testing equipment.