You turn the key to start a tractor, combine or truck and hear only the maddening sound of the starter solenoid clicking. Is the battery dead or easily fixed with a quick recharge?
In the past, deciding whether a battery was dead or salvageable was a frustrating experience because battery testers were sometimes unreliable or prohibitively expensive.
The "cheese-grater" battery testers found in many farm shops, nicknamed because their chromed, slotted case looks similar to the kitchen tool, often give faulty readings when testing heavy-duty diesel engine batteries. While high-end cheese-grater testers can accurately test diesel-duty batteries with up to 1,000 cold cranking amp (cca) capacity, most of the testers found on farms are 150- to 200-cca units designed for automotive use.
The carbon pile battery load tester traditionally used by professional mechanics is reliable but expensive. Carbon pile load testers actually simulate, for 15 seconds, the load of starting an engine. Industrial-duty carbon pile testers can test batteries with up to 2,000 cca but are heavy and can cost more than $2,000. Farm-duty carbon pile testers cost $500 to $750 for units that handle batteries up to 1,200 cca.
Digital testing. Fortunately, a new generation of handheld digital battery testers offers impressive testing capability for remarkably low prices.
"Digital battery testers test the relative conductivity of the battery, then use a built-in microprocessor to predict the battery’s condition," says Scott Crerar of Auto Meter. "Their design doesn’t put any load on the battery as part of testing.
"Digital battery microload testers, on the other hand, put a load on the battery for 2 seconds, then use algorithms in a microprocessor to predict the battery’s condition," Crerar says.
Jim O’Hara, vice president of marketing for Clore Automotive, manufacturer of Solar brand digital battery testers, notes that both types of digital testers can offer accuracy comparable to traditional carbon pile testers.
Another advantage of digital battery testers: They don’t require batteries be fully charged before testing.
"With resistance testers, you have to drag a battery charger into the shed to charge the battery before you can test it to decide if you need to replace it," says Larry Smith, technical services adviser with Clore Automotive. "Digital battery testers will test partially discharged batteries without having to mess with battery chargers."
When purchasing a digital battery tester for farm use, identify the largest batteries that will be tested and select a tester able to handle that capacity. Prices vary depending on the tester’s capacity. Digital testers are available for as little as $25, while digital micro-load testers retail for $90 to $350.
Smith notes that with farm-duty batteries costing around $150 apiece, a properly sized digital battery tester can pay for itself in a single use by preventing unnecessary replacement of a questionable battery.