I bought a couple of these from Gooloo after seeing a Project Farm test.
I'm satisfied. They work fine. I don't know if it's pulled a battery back form the depths of 6 volts, but it has revived more than one dead battery.
(As to the Schumacher, same story. I had a Craftsman (rebranded Schumacher) forever. When I bought my 911 I bought a Schumacher tender that lasted maybe a couple of years before it started whining. Lobbed it into the trash.l