Most modern 12-volt car batteries are designed to last somewhere between four and five years. Problems might arise during that time, however, that may cause the battery to malfunction. For example, excessive corrosion that accumulates on the terminals can drain the battery's voltage. Accidentally leaving on the lights or other accessories also will drain the battery. An insufficient charge from the alternator also can be the culprit. With a few tools, you can troubleshoot battery and charging-system problems.
Examine the battery. If it's coated by dirt or grease, clean it off with an old rag. Look for cracks or signs of leaks in the battery case. If it has been compromised, you must install a new battery.
Check the terminals for corrosion, which can drain the battery and cause a bad connection. If the battery is still in your vehicle, loosen and remove the clamps using a small wrench. Clean both the clamps and the battery posts with a mixture of 2 tablespoons of baking soda and a pint of warm water. Pour the mixture onto the clamps and posts and brush them. When you're done, coat the terminals with petroleum jelly and snugly reconnect the clamps.
Charge the battery using a 12-volt charger. Ensure the battery gets a full charge and then allow it to sit overnight without being used.
Connect a 12-volt (DC) digital voltmeter to the battery. If the battery is in a vehicle, the engine and all electrical components should be turned off. Also, you must ensure that you connect the voltmeter correctly by attaching its positive clip to the positive battery post and the other clip to the negative post.
Confirm the readout on the voltmeter. A fully charged battery that has been allowed to sit for about 12 hours should read in the vicinity of 12.5 to 12.8 volts. A reading below 12.4 volts would indicate that your battery cannot hold a full charge and has to be replaced.
