Does anyone know where to get a 21700 to 26800 battery adapter? I have a nice one that came with my Lumintop D3 and would like a couple more. I tried contacting Lumintop on their website and their AliExpress store to see if it can be purchased separately but got nowhere. They kept pointing me to unrelated products. Language barrier I guess. I know people are doing it with these O-rings and these Battery Spacers but I'm not comfortable with loose pieces in with lion batteries.
I think your misunderstanding me. A 21700 to 26800 battery adapter simply makes a 21700 battery the same size as a 26800 battery that can be used in any 26800 host flashlight regardless of what it has for threads. I have 20 amp QB26800 batteries and a lot of more powerful 21700 batteries that don't heat up when running at high levels. I want more battery options for an extended power outage.
Other way round is a bit easier. Usually a couple of rubber bands around the cell to fit the width. Protected cells if extra length is needed. Straight out adapter, I haven’t seen one yet, or one I remember.