Hey there 
Just a simple question: What does it need for a battery to fit in a Convoy S2+?
Chunkiest cell I have is an old protected EVVA. It measures 68.9mm x 18.4mm - thatâs protected button top with double wrap and a sticker. In the older S2 and S2+ lights it fits fine lengthwise with a smidgen of extra room still, but itâs a pretty snug fit for the diameterâŚwouldnât want to go any fatter unless you donât mind unscrewing both ends to push the cell out with a finger. Newer trapezoidal S2+ fits about the same. The newest versions with the flattened (not really square-cut) threads have a slightly larger inside tube diameter, same length. Iâd ballpark a 70mm x 18.6mm as the max acceptable. Standard cells, no worries with any of them.
A perfect fit is when you have to sling the battery out onto a blanket and it makes that hilarious âFOP!â noise.
69.2mm x 18.7mm still fits in my older Convoy S2+.
The max width can actually vary depending on the batch. I personally recommend non re-wrapped 3500mAh unprotected 18650s.
The Sanyo/Panasonic NCR18650GA Protected 3500mAh which measures 18.7mm x 69.0mm fits fine. I wouldnât go any wider though.
My 3400 mAh protected Keeppowerâs are 69.1mm long and they fit well.
The inside diameter of my S2+ bodies is 18.8mm.
Beware: because of the way they are produced, the S2+ body AND protected batteries are NOT perfectly round. So my Keeppowerâs not always fit. Often I have to rotate the battery a bit to get it in. But whatever you do: donât apply force when inserting batteries.
Thank you all very much! 