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Video:How to Know if a Car Battery Is Dead

with Nick Jaynes

Learn about the best way to know if a car battery is dead. Here, see helpful tips for knowing if that's the issue or if the problem is more serious.See Transcript

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Transcript:How to Know if a Car Battery Is Dead

Hi I'm Nick Jaynes from DownForce Motoring for About.com and this is how to know if your car battery is dead. I'll be using information found on About.com's auto repair guide site.

Why It's Difficult to Know if a Car Battery Is Dead

It's all happened to us before: we come out to our car in the morning and it just won't start. Unless you're a trained mechanic, it's hard to know what is causing your car not to start. But here are a few helpful steps to follow to help diagnose what's going on with your car. It turns out; the most common reason cars refuse to start is a dead battery.

Tips for Knowing if a Car Battery Is Dead

A dead battery can be caused by many factors: you left a dome light on over night, your alternator is worn out and recharging the battery, or the battery has simply hit the end of its useful life. If you have a battery tester that can measure cranking amps and voltage, you can test your battery to see if it's weak. At rest, the battery should be at 12.5 volts. And with the car at idle, the battery should be at 13.5 volts. This is because, in order to charge the battery, the alternator needs to create at least one more volt than normally required in the system. If you can't test it yourself, you can test the battery indirectly by jump-starting the car. If it starts right away, your problem is most likely a dead battery. Jumping the car will tell you that the battery is the no-start culprit because jumping essentially circumvents the battery with the battery from another car. If the car cranks and fires on the power provided by another healthy battery, you know you need a new one.

Knowing When It's Time to Replace the Car Battery

At this point, it's time to replace the battery. You can do this yourself by going to an auto parts store or in some areas there are mobile auto battery sales that will come to you. AAA has just such a mobile battery sales unit. Just know if you buy a battery from a mobile auto battery replacement company, you will pay top dollar for the convenience.

Once you've replaced the battery, clean the battery connections to ensure good contact between the battery cables and your brand new battery. This way you are guaranteeing your new battery will receive the power it needs from the alternator and make certain you get as much usable life from the battery as possible.

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