I have bought 8 of these. 2 are no longer working - are no longer charging the batteries. One gave in after about 4 months of usage, the other in about a month of usage. That is an extremely high failure rate even if i were to be the most unlucky person on the planet. And waveshare service sucks. They basically demand all sort of proofs that the product is really not working until you give up trying. Had similar experience with other type of waveshare upss too. And these are not cheep either. I guess i just have to stop buying waveshare. Of course the rating is for the product, not the store.