Oh, and the display can't be read in bright sunlight. That's the first thing I noticed when trying to use it, actually. I didn't know it was even on and working until I cupped my hands around the display to see that, indeed, my battery's voltage was in fact displayed. Very dimly. A better screen type would have been a great idea (in a garage, this likely wouldn't be an issue).This unit does two types of tests: one, with the car off, which tests the battery's voltage and (somehow) its cranking capacity. My van's 685CCA battery came in at 677, and got the green LED. All good there. It seems well built, and the clamps (permanently attached) are decent. Make sure you get a good connection to the battery posts, or the CCA reading will be inaccurately low (I had to adjust a few times to get it right).For part two, the charging system test, you kind of need a second person to do properly. One standing at the battery to watch the readout and control the test, and a 2nd person in the driver's seat to start the car, then keep it revved to 1200-1500 RPMs, and then turn on the vehicle's loads (hi-beam headlights + full-power fan + rear defroster recommended) for the load test. At each step, you press a button or two on the device to move it forward, and it doesn't store the voltage, so running back and forth from device to vehicle controls isn't ideal.The tester works well once you figure out how to navigate the device's menu and learn what the odd 4-letter contractions mean for various parts tests this thing can run (there's a cheat sheet on the back of the device). There had to be a more straightforward way to run through the steps though.Anyway, it's a handy device, and tells me more about the battery than just my multimeter did... but not that much more (just the current CCA cranking capability of the battery). If that extra bit of info is worth the cost of the device to you, then by all means get this tester. If you're okay just knowing voltage, and already have a multimeter, it tells you almost as much info as this device does, is far more "all purpose", and you can get one that will work fine for under ten bucks (harbor freight, etc).