Rick's Free Auto Repair Advice

Test car battery before winter

Test car battery before winter

Why it’s important to test your car battery before winter

A battery produces less power in winter

A lead acid battery makes power through a chemical process. That chemical process slows down in cold weather and increases in warm weather. So in the dead of winter, a healthy battery can only create about 1/2 the power compared to summer power production.

Your engine needs more power in winter to crank and start

It takes more amps to spin a cold engine on startup than it does to start that same engine in warm weather.

A battery problem will show up more readily in winter than summer.

With less available power and higher power demands, a weak, worn, or sulfated battery will fail more often in cold weather.

A thorough battery test is the only way to determine your car battery’s condition

Modern battery testers are pretty good at predicting a car battery’s condition.

A car battery voltage test isn’t a good predictor

A voltage test only tells you the battery’s state of charge (SOC) today. It can’t be used to predict how your battery will behave tomorrow or a month from now. Instead, you want to know the battery’s state of health (SOH).

To do that, a battery tester must conduct an internal resistance/conductance and simulated load test.

Why you must test your car battery’s internal resistance

Internal resistance increases over time

Battery Cell to bus resistance

Each battery cell is connected to the lead bus and to the positive and negative posts. Over time, the plate/bus connections can develop increased resistance that reduces the battery’s ability to accept a charge and to create power.

Battery plate resistance

Over time, the lead plates in your battery deteriorate or accumulate a layer of sulfate crystals, which increases internal resistance.

Corroded battery terminals are a major cause of increased resistance

Severe battery corrosion is pretty easy to spot. But your corroded battery terminalsbattery connections can look find but still have high resistance. Unless you perform a voltage drop test, you can’t judge battery terminal resistance.

How a car battery SOH tester works

Locate the label on your car battery that shows the cold

Solar BA9 battery tester

Solar BA9 battery tester

cranking amp rating and enter that into the tester, along with the rated voltage and battery type (standard lighting ignition [SLI] versus absorbed glass mat [AGM])

Press the test button.

The tester will perform an internal resistance/conductance test and a simulated load test. The results will show the predicted CCAs available and whether the battery passes or fails.

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©, Rick Muscoplat

Posted on by Rick Muscoplat


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