I've been having some doubts about my fairly new car battery (Interstate, 700CCA) recently and wanted to make sure I test it before taking it back to the store. I am aware that batteries will lose charge if the car is not used for extended periods of time (which is my case due to WFM for months), but I was thinking that it would take much longer to a new battery to get there, maybe at least 1-1.5 months, especially in nice weather. I have been driving my car about every couple weeks or so, but mainly short drives. I thought that maybe the battery I picked did not quite happen to be the pride of Interstate product quality. Since I've wanted to own one of these battery testers for a while now, I figured that this situation would be a good time to get one, so after looking through several models to get familiar with the common feature set offer vs. cost, I settled to this Konnwei KW650, even though I was a bit reticent about the brand unknown to me. There are a bunch of these testers available, many of them offering similar if not identical feature package, even though the prices differ a lot in some cases, but the reasons that made me go for this one were the nicer processing speed and display, car starting voltage waveform capture and the software update capability. I figured that my risk would be minimal considering all the good reviews and Amazon's easy return policy. Well, I must say that I am very happy with my choice; this one is a keeper. After updating the software as soon as I received it, which was pretty easy to do BTW, I checked my battery and found that even though it was in a pretty badly discharged state, the tester showed that the battery was in very good condition and just needed a good charge. The state of health was 100% and the state of charge was shown to be only 10%. I have also tested a known weak battery I had stored until I can find the time to dispose of it. I tested it both before and after charging it, and in both cases it indicated a very low state of health and prompted replacement. I was planning to rent a professional battery tester and check the full instrument accuracy for parameters like the battery resistance, SOH, SOC, but at least from what I am seeing so far from my tests (lead-acid battery only) everything makes sense. The voltage measurement had only a small accuracy deviation of 0.06-0.1 max over a wide measurement range when verified against a professional meter, but that is meaningless for the purpose of this tester. The voltage ripple was also slightly off, but you can see some of that even when comparing more expensive equipment. The min/max voltage captures during engine start were also reasonably accurate. Considering the cost and intended purpose of the device, I believe that it is more than adequate for the job, and in my opinion, paying any more for a known brand would not be justified from the performance stand point. At least not for my home garage use. In terms of workmanship, I have nothing to object: It comes in a nicely looking plastic case, light weight and just the right size to hold with one hand, clear color graphic display with an easy and intuitive user interface. It has thick yet reasonably flexible 38 inch cable to protect the 4-wire Kelvin test leads, with solid connections to the battery connection clamps. I wish the cable were just a bit longer to reach the vehicle cabin when performing some of the tests more comfortably from the inside, like the car charging system. Not a deal breaker, because these tests are still easy to accomplish, but it would have been more comfortable that way. Now the one feature I was hoping to have on this device, was to be able to factor in the battery temperature into the CCA measurement and SOC calculation, as temperature is a huge factor in battery performance. Again, not a deal breaker at this price for me, but since most higher end devices can compensate for temperature, I believe that it would be a great feature addition and a cheap way to gain an edge over the competition. I wouldn't expect the addition of a battery post temp probe/sensor (although I would actually pay for the cost difference) but at least by manually entering the batt. temperature during battery test setup. Since the software can be updated online, I am hoping that this feature can be added later, and perhaps along with some other good things in the future. Who knows, maybe Konnwei is listening.
