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In the Shop

RSS By: Dan Anderson, Farm Journal

As a farm machinery mechanic and writer, Dan brings a hands-on approach that only a pro can muster. Along with his In the Shop blog, Dan writes a column by the same name as well as the Shop Series for Farm Journal magazine. Always providing practical information, he is a master at tackling technical topics and making them easy for all of our readers to understand. He and his wife, Becky, live near Bouton, Iowa.

When The Spark Is Gone

Jan 31, 2010
 Cold weather brings to dealerships and auto parts stores a parade of customers bearing batteries. Customers assume a quick test will determine whether their batteries are "good" or "bad." 

The truth is that there is no simple, quick test for batteries. Tests conducted by a major farm equipment manufacturer showed half of batteries warrantied as "bad" were actually "good, " but merely undercharged, low on fluid or had been tested incorrectly.

I'm not a battery expert but have learned a few facts that help me do a better job when testing batteries.

-Batteries should be fully charged before testing. Make sure all cells are filled to the proper level. (Never add acid to a battery. Add only water, and distilled water if possible.) Use a "smart charger" that slow-charges batteries, monitors their condition and automatically ends charging when the battery is at capacity.

-Use a quality battery tester. The shiny chromed battery chargers with slots on the sides that look like cheese graters are "okay" for testing small car batteries but inadequate for testing tractor and farm machinery batteries. The best way to test high-capacity batteries is with a carbon pile load tester. Such testers can be adjusted to put a simulated load on batteries, and do an excellent job of identifying batteries that test "good" but fall on their face when an actual load is applied. FYI, carbon pile battery testers capable of testing farm batteries range from $500 to $700. 

(There is a new breed of digital battery testers on the market priced from $50 to $200 that claim to be able to load-test large batteries. I'm uncertain if these lightweight and convenient testers can compare to good ol' carbon pile testers. I've got a mid-range digital battery tester, but haven't yet passed judgement on how trustworthy it is. When in doubt, I still drag out a carbon pile tester.)

-Even if a battery tests "good", check it with a hydrometer. Battery hydrometers check the specific gravity of battery fluid. A certain percentage of batteries test good, but fail under load because the battery fluid is off-kilter. 

Like I said, I'm not a battery expert. But I've learned that REALLY testing a battery takes time. Time to allow it to fully charge, time to use a quality tester to load-test it, and time to double-check the battery's condition with a hydrometer. If you haul a "dead" battery to your local battery retailer, slam it on the counter and ask for a "quick test," there's a 50-50 chance you'll walk out with a brand new battery, whether you need it or not.

Not because they're trying to shaft you, but because you asked for a quick test, and the quick test said your battery needed replacement. Sometimes you get what you ask for.

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COMMENTS (3 Comments)

Dan Anderson
These are comments, not endorsements: Northern Tool, NAPA, and many machinery supply stores sell a variety of carbon pile testers. I found carbon pile battery testers on the internet for as little as $39 and as much as $725. Schumacher, Autometer, Electronic Specialties and Solar are just a few manufacturers that make carbon pile testers in a range of prices and capacities. When buying a carbon pile tester, realize the test procedure is to set the tester to 1/2 the Cold Cranking Amps (CCA) rated on the battery. Therefore, a 500 amp tester could test a battery rated at up to 1000 CCA amps. In our shop we use an Autometer unit rated at 800 amps. It cost around $500 15 years ago and has proven extremely durable and reliable. Shop with care for battery testers, ask lots of questions and know the CCA rating of the biggest battery on your farm before buying.
9:38 AM Feb 1st
so, give me a battery checker to buy! brand name and where to buy.

5:08 AM Feb 1st
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