Chicago Electric Power Tools / Battery Load Tester 91129 Carbon Pile Tester / Product design and assembly flaws / safety
500 Amp carbon pile 12 V battery tester, Chicago Electric Power Tools Item 91129, presumed to be marketed exclusively by Harbor Freight Tools --
* 1st Batter Tester purchase from local store - Load know stripped after 5 to 10 uses. Felt bad from the 1st use, but user did not realize the knob threads were cross-threaded. Made 70 mi round trip to exchange. Battery tester clamps left large marks in the battery terminals, apparently because they are cheap, thin gauge steel coated with a very thin coat of copper.
* 2nd Battery Tester / in-store exchange -
(1st use): The Amp meter deflected to about 130 A on a new 12 V Optima battery, (rated at 800 CCA). A 2nd new Optima battery was tested and again, the Amp meter deflected to about 130 A, then after about 10 to 15 seconds deflected to 500+ Amps. Whoa! By this time, the battery tester clamps had melted 1/8"+ deeps grooves into both battery terminals of the 2nd battery. It was then seen the 1st battery also had melted grooves, just not quite as deep as the 2nd. These expensive new batteries looked like crap and could not be repaired.
(2nd series of use): The battery load tester seemed to be indicating reasonably well for about 5 to 10 tests, but there was a smell of burnt paint and electrical insulation. A look down through the vents showed an orange hot bolt. The 1st battery tester did not seem to do this. Another couple of uses and this battery tester failed to display Amps, but not before another battery had deep grooves melted in by the cheap clamps at the time the Amp meter was failing completely.
* 3rd Battery Tester – Purchased on a side trip, did not have defective 2nd Battery Tester with me to exchange. Battery Tester load knob lubed with nickel, high temperature Never Seize, which helps significantly. This one seems to work better but the clamps WILL melt grooves into a battery’s terminal undergoing the standard carbon pile test because they are cheap steel coated with very thin copper. This is unacceptable for a product rated at 500 A, 12 V use. User purchased a 30+ year old Sun VAT-28 that had NONE of these problems.
* Back to the 2nd Battery Tester problem – The covers of both the 2nd and 3rd Battery Testers were removed and the 2nd Battery Tester was found to have a plated steel bolt where the 3rd Battery Tester had a brass bolt. DANGEROUS assembly defect. This caused a metal strap to overheat and the Volt meter wiring to melt completely. A 10 ga copper wire was installed connecting the meter and bypassing the dangerous steel bolt. A fully charged 800 CCA Optima battery was then tested but the meter only deflected about 130 A. The load was quickly removed. It is now obvious the Chinese assemblers changed the Amp meter calibration to compensate for the dangerous steel bolt substitution!
The 2nd Battery Tester is dangerous junk, and the 3rd Battery Tester, if used to 75% of its rating, will leave unacceptable grooves in the battery terminals.
The 1st email to Harbor Freight Tools was answered, and they asked for a little more info. This info was forwarded within a couple of days. The 3rd and 4th emails to them, sent several weeks later and referencing the 1st email, went unanswered. UNACCEPTABLE ! This is a more serious accident waiting to happen.