You get in your car and discover that neither the engine nor the lights turn on. Once you've powered up your car, you can find out if you need a new battery or alternator. Follow these steps to check a car battery.
Steps
Method 1 of 3: Check the Battery with a Voltmeter
Step 1. Turn off the ignition or ignition switch
Step 2. Remove the cover from the positive pole of the battery
Check and clean both poles.
Step 3. Connect the positive lead of the voltmeter to the positive pole of the battery
Normally, the positive lead of a voltmeter is red.
Step 4. Connect the negative lead of the voltmeter to the negative pole of the battery
Step 5. Check the voltmeter
If the battery is in good condition, the voltage should be between 12, 4 and 12, 7 volts. A reading lower than 12.4 volts indicates that the battery needs recharging.
- If the reading is less than 12.2 volts, perform a maintenance recharge, which means a slow recharge. Then check again.
- If the reading is greater than 12.9 volts, you have a voltage surplus. Turn on your high beams to dissipate excess voltage. An excess of voltage could indicate that the alternator is overcharging the battery.
Method 2 of 3: Check the Battery with a Power Tube
Step 1. Remove the cover from the positive pole of the battery
Step 2. Connect the positive lead of the power probe to the positive pole of the battery
Normally, the positive lead of a voltmeter is red.
Step 3. Connect the negative lead of the power probe to the negative pole of the battery
Step 4. Glue the probe tip to the positive pole of the battery
Check the voltage reading.
Step 5. Check your feeding tube reading
If the battery is in good condition, the voltage should be between 12, 4 and 12, 7 volts.
Method 3 of 3: Check the Battery When Starting the Engine
Step 1. Start the engine by turning the car's ignition until it works and hold it for 2 seconds
Have an assistant start the engine while you check the battery voltage drop.
Step 2. At the same time as starting up, check the feeding tube reading
It should not be less than 9, 6 volts.
A battery reading less than 9.6 volts indicates that it is sulfated and will not hold or accept a charge
Advice
- Most car batteries last 4-5 years. In hot climates, they may only last about 3 years. If you recharge your battery and find that it won't hold a charge while your car is off, then replace it.
- If you get a new battery, just be sure to dispose of the old one according to the laws imposed in your state. Auto parts stores usually take care of disposing of dead batteries for you.
- Test and recharge your battery at the nearest auto parts store.
- Before purchasing a new alternator, do a more detailed system check.