I thought about the possible use of 18650 or Teslas batteries for a week. But I dropped the idea because of some issues I saw with the idea



Basically my idea was to have two of them, one on each side which would be accessible via normal battery slide covers similar to any other battery slide cover used to cover AA or AAA etc batteries on most devices. The batteries could then be replaceable . The beauty being they would be on the edges and leave the entire large central area for the PCB etc.

You also could add a third battery at the bottom front.



Problem is though, that the batteries would then be in the grip areas in your hand. Of course you know people would complain about the heat then. Then there is the issue of thickness and what that would do to the WIN2 case. That said, it seems the WIN 2 will be thick enough to handle 18650 batteries. Then there is the weight, they weigh more than the flat battery variety. The biggest issue though is since there would be more than one battery, they would both need to be replaced with similarly charged batteries. If one of the batteries was of a different charge, that might be not very good. Of course you could solve this by making them not replaceable - that would eliminate a reason to do it though.



For reference , I think the Nvidia Shield Portable uses 2 or 3 18650 batteries

I also noticed that the 18650 batteries seem to be lower in capacity than quoted on the package. I watched a number of people do tests on them on Youtube. The best onces I saw were the Panansonics which had a tested ~ 3250mAh each