Review on Watt Meter Power Analyzer - Greatlong 200A Power Analyzer with High Precision Digital LCD Screen for Voltage, Current, Power, Charge, and Energy Measurement by Danny Kamerer

Extremely Inaccurate. Installed on my e-bike to measure Wh and Ah during a 45 mile ride. My battery is advertised as a 48V 20Ah battery. To calculate Wh, multiply V x Ah = total Wh for the battery. In my case 48 VX 20 = 960Wh. So how much battery did I use during my 45 mile trip? Judging by this piece of junk, it measured 5ah and 284 Wh! It is impossible. As I suspected, the battery was almost dead and only lasted 10 miles on my next ride the next day. With another 2 Ah. So either my 20Ah battery is actually a 7Ah battery, or the meter is junk. There seems to be about 20 different brands selling the exact same meter. All unknown companies from China rename the same equipment. Buyer Warning.