When to Replace a Battery

Winter is when we usually worry about batteries, but it’s frustrating how many batteries in machines turn up dead after a summer of sitting in the shed.

By Dan Anderson

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August 03, 2022 04:36 PM

Battery disconnect switches, aka “kill switches,” discourage machinery theft and reduce problems with batteries being drawn down during storage.

Winter is when we usually worry about batteries, but it’s frustrating how many batteries in ma-chines turn up dead after a summer of sitting in the shed. Time to test that battery to see if it needs replacing.

There are two basic types of battery load testers: carbon pile load testers and hand-held load testers.

Carbon pile load testers are big, heavy and expensive, but simple and foolproof. Quite simply, you determine the cold-cranking-amp capacity of the battery to be tested, set the load tester to half that CCA, then push a button. These old-school testers use a high-resistance carbon pile to severely load the battery for 15 seconds and then display how much charge the battery has left as either “Pass” or “Fail.” Plan on paying $500 to $1,000 for a carbon pile load tester capable of testing 4WD tractor and semi-truck batteries.

That’s compared to smaller computerized hand-held battery testers that briefly load a battery, then use algorithms to calculate and estimate the battery’s capacity. The quality of hand-held battery testers varies with price. $100 hand-held testers are adequate for automotive and light-duty testing.

Farm equipment and semi-trucks with batteries above 500 CCA require testers costing $200 or more. Handheld battery testers used in professional repair shops can cost north of $500, but predict battery condition of high amp batteries nearly as well as a carbon pile tester.

Be aware that Grandpa’s old battery tester, the one that looks like chromed cheese grater, is strictly for automotive-type testing. Those testers are a lightweight version of a carbon pile tester, and not designed for today’s big truck and tractor batteries.