FJC 45115 500 Amp Heavy Duty Carbon Pile Battery Tester for Car, Truck, Marine & RV - Professional Automotive Battery Load Testing - Perfect for Mechanics, Auto Shops & DIY Enthusiasts

I always review things with respect to their cost. This is a good unit for the price. In my opinion, the quality is good and a little better than i expected at this price point. I opened it up and was pleased to see heat shielding on cables and near the circuit board (used for a 10 or 15 second timer that buzzes). The connections looked solid and I torqued a few of them down more. The clamps and cables are pretty good and flexible.Before I even used it I wired in a little 12V cooling fan (like what a PC uses). It blows on the carbon pile and that helps it shed heat a lot faster. I hooked it up to a battery and pulled 400 amps for 15 sec and did this about 4-5 times in a row and it got hot but I took it apart later and didn't see any burn marks or signs of excessive heat.When I pulled 400 amps, I noticed that I could reach 400 amps then the gauge would slowly drop lower as the heat increased the resistance in the carbon pile and connections. So in 15 seconds it might go from 400 down to 350 or so. When I pulled 300 amps through it the gauge held pretty steady. So the connections seem to be right for 300 amps but your pushing them at 400 amps (but I don't think you need any more than that really).Lastly I adjusted the analog voltmeter. Most people adjust these by setting them to zero when you have nothing hooked up, but I don't think that's the best way to do it and is often not accurate. I think it's best to feed in the voltage that matters the most to you, then adjust it to exactly measure that voltage. So I used an adjustable power supply to feed 9.6 volts into it (you could probably use a 9V battery too) then I adjusted the gauge up 0.4 volts so it read exactly 9.6V. The gauge was perfectly on zero before I adjusted it now it's reading 0.4V with nothing hooked up, but it's dead on at 9.6V and 12.6V now. That's the reason I only adjust them with an actual voltage hooked up.The ammeter is plenty accurate for my liking it measured 50 amps when my amp clamp measured 55 and it measured 400 when my clamp measured 425. Again, I don't think you need excessive accuracy with the amperage. I think an analog gauge, even on an expensive model, would be about this accurate.Most of the stuff inside it looks repairable if you ever needed to repair it and yes I'd probably buy it again if I needed to.