Tech Stuff

Battery testing basics

After examining the photo, what do you think? Is it time to replace this customer’s battery?
<p>After examining the photo, what do you think? Is it time to replace this customer&rsquo;s battery?</p>

Weber is president of Virginia-based Write Stuff. He is an award-winning freelance automotive and technical writer and photographer with over two decades of journalism experience. He is a National Institute for Automotive Service Excellence (ASE)-certified Master Automobile Technician, and has worked on automobiles, trucks and small engines. Weber is a member of the Society of Automotive Engineers (SAE) and numerous other automotive trade associations. He has worked as an automotive service technician, a shop manager and a regional manager for an automotive service franchise operation.

The cold snap that recently swept through most of the nation caught many folks unprepared as roads closed, pipes burst and batteries failed.

Many technicians began their career because they marveled at things mechanical. We like to watch things going ‘round and ‘round, and up and down. We understand the mechanical stuff, but when it comes to electricity, some techs tend to stumble. Electrical system diagnosis seems to be the bane of many technicians.

You can neither see electrons flowing through a wire nor the chemical’s ions moving in the battery. This is an area of auto service resulting in far too many guess-and-replace attempts at fixing. That includes batteries, alternators and starters.

It should not be so.

You need a window into the system. That window can be oscilloscopes, digital multimeters or special testing tools.

It usually starts with a customer on the other end of the phone complaining that their vehicle will not start (naturally, they’re referring to an engine no-start). The battery is dead. Even before you send your wrecker to get the car, you check your battery inventory to see if you have one to fit.

It may be a guess or a hunch, but not all starting problems are the fault of the battery. But how do you know?

You perform a diagnosis, just as you would with any vehicle problem. It helps to understand the basics of battery technology to understand what your tests are revealing, even if you use a modern battery-charging-starting system tester.

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