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The product very accurate did everything I tested for.
I happen to be a certified mechanic so you will need
to know how to read the meter.
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Right now there are at least seven different brands of these very similar 500 amp units offered on Amazon, and Harbor Freight has one too. They all appear to be nearly identical except for the paint color and graphics. Prices range from around $50 to $160.There do appear to be minor differences, though. If you look carefully at the photos you can see that two of the models sold on Amazon have small wires running alongside the positive and negative cables between the battery terminal clamps and the unit. In applications like this, where large currents are flowing, this is typically done so that the volt meter can accurately read the voltage at the clamps through the smaller wires, so the voltage drop through the large cables does not affect the accuracy of the voltage reading. This would be a worthwhile feature, and the funny thing is that the cheapest one sold here on Amazon has it, along with the most expensive one. The others, including the one I'm reviewing here and the HF model, do not have the extra wires.
I first bought a Sun VAT-40 for my shop in 1977, which was the "gold standard" of testers like this for many years. I was also a Sr Tech Trainer for one of the Japanese auto companies, and was later in charge of their special tools and diagnostic equipment program. I did not, of course, expect this unit to perform at the same level as more expensive professional equipment, but at some point if the functionality and accuracy are too bad then the tester is not usable. If the voltage reading, for example, is way off then you may either fail good batteries or keep those that should be replaced.
My experience with this unit is about the same as some of the other reviewers of the similar testers sold here on Amazon. I had actually ordered this one instead of one of the less costly testers thinking that the better reviews of this one possibly indicated that it was higher quality. Now, I don't think that is the case. At low current loads, the amp needle jumped around quite a bit as the load knob was slowly adjusted -so it was difficult to set the current to a specific value due to the erratic variations. This was not as apparent at the higher current levels used for larger batteries. As some reviewers of the other similar testers have also mentioned, the current reading tends to increase slowly during the test -so you have to keep fiddling with the load adjusting knob to keep the current where it should be.
Also, using two high-end Fluke DVOM's (one is a bench model used in an electronics lab), I found that the volt meter readings were quite inaccurate. I'm not talking about nitpicking, I'm talking about being off enough to compromise the results of the test. Also, the voltage reading was inconsistent in a kind of unpredictable way as the load current was increased. In other words, it was not as simple as saying that it was off by a certain percent or was off by a certain specific amount (offset/zero adjustment). It is almost as if they tried to design in some compensation for the voltage drop through the cables at higher current loads, but didn't do a good job.
My feeling at this stage of the game was that these six or seven different "brands" of these testers are probably all about the same -so why buy the more expensive one instead of the cheaper one? Also, with a 25% off coupon I was able to pick up one from Harbor Freight for just over $41 to compare against this $100 tester. Looking inside through the ventilation slots, and generally examining the units, they appeared to be nearly identical (except for paint color, etc). At first the load adjustment on the HF unit was horrible until the knob fell off -heh, heh! Once I tightened it up the load adjustment (especially at lower current values) was a little smoother than this unit. The severe inaccuracy of the volt meter was about the same.
I did not verify the accuracy of the current meter on either this unit or the HF unit. I have accurate DC current clamps that I will use when using this tester on customer vehicles (along with my Fluke 87 DVOM for voltage readings).
Conclusion: I don't think there is any significant difference between this unit and the HF tester that cost less than 1/2 of this one. The meters on both of them are not accurate enough to be taken seriously. Yes, you can see if a battery is really good or really bad, but the borderline ones will be the problem. I decided to return this one and keep the HF unit to just use it for the adjustable carbon pile, while using my other meters for the voltage and current measurements.
Why two stars? If 5 stars is an "A" and 1 star is an "F" then I think 2 stars is about right -a "D" (barely passing, needs improvement). Not really good enough for the application, and overall quality seems shaky. Too bad -if it was just a little batter it would be okay. Not great, but okay. I would gladly pay $100 to $150 for a unit that had meters with enough accuracy to do the job, and a quality level that didn't make me think it was going to fall apart after a few uses. If some of these can be sold for as little as $50, then it seems like they could make a "deluxe" one based on the same design and sell it at a decent profit for 2 or 3 times more.
Hope this helps -happy testing!
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