Is that battery really dead?

Date:3 August 2013 Tags:

Q: My car’s been having trouble turning over in the morning. I replaced the battery, but the problem recurs aftera few days. What should I do?

A:  Although it’s possible that new battery is bad, you may have another problem. Just to eliminate the easy fix first, drive down to the local spares store or battery centre and have them test the new battery. A load tester measures how well the battery can store and release electric charge. If the battery tests good, that means there’s a problem with the charging system, or that something is drawing power when the car is off.

To test the charging system, start the car and let it idle in a well-ventilated place. Grab your multimeter and set it to the DC-voltage option. Although cars operate at 12 volts, the charging system should deliver a steady 14-volt output. Measure this by placing the multimeter’s positive probe on the positive terminal of the battery, and the negative on the engine head or block – something that’s heavy and metal and definitely part of electrical ground. If the voltage reads below 14 volts, the alternator could be going bad. Alternators don’t usually go before the 150 000 kilometre mark. If there’s a red battery light emblazoned on your instrument cluster, this is probably the case, although it pays to check all your fuses before replacing the alternator; sometimes a  blown fuse will affect proper charging, as crazy as that sounds.

If the output is at 14 volts, the cause is likely a voltage leak, a condition in which something keeps consuming electricity, even though it shouldn’t be, when the ignition is off. Turn the car off and take a voltage measurement at the battery terminals.

Come back a few hours later and remeasure. If there’s more than a half-volt difference, it’s likely that something is drawing power. Chasing down a problem like this can be a huge headache, and it might be worth taking your car to a workshop.


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