Further to the ShineMate discussion, back in November 2019, I was one of the first buyers of their battery powered units, the 5-inch EB351-5/15 and 3-inch EB351-3/12.
I was coming from a basic Porter Cable style polisher fitted with a 6-inch backing plate. I have not used that machine ever since, even thought I kept it "just in case".
My only complaint being that the 3-inch machine is physically the same size as the larger 5-inch machine. This basic body is shared across the 3, 5 and 6-inch machines. Since these were released, ShineMate have launched two others that seem to rectify this.
First was the EB350-3/12, which has a redesigned body with superior integration of the battery and relocated speed control. These use a 2.5 Ah 18v battery, but the 5.0 Ah can be used as well. They also sell a rotary version too -
The second was only released last month, the EB210 Mini -
Think of this as a PXE-80 competitor (knock off), with the ability to quick change between rotary and D/A functions and 1, 2 and 3-inch backing plates. They run off a smaller 10.8v battery system and are supposed to be very torquey.