Bests & Worsts Reviews from Amazon

The power bank just wasn't performing well, so I checked it with a mAh meter and a dummy load. (And yes, I know how to do it.) All Power Banks have inefficiencies and they convert 3.7 volts to 5 volts, so you will never actually see the rated output (in this case 26800 mAh). But this one never measured above 11000 mAh, or about 57 watt hours (rated at 99.2 wh). After several tests, the highest efficiency rating I could get was 56%. Unacceptable. Having said all that, the Power Bank can be useful for many applications...it just doesn't live up to it's advertised specs. It is possible that I received a bad unit, but I suspect they are all the same. I returned it.