The Opus BT-C3100 is one of the best Multi Charger for NiHM and 18650 Lithium cells on the markt.
But his Little Fan makes it unsuable in in your near environment.
This "idea" ist not new, there are some Fanmods out there, but i havent found a printed one.
Also the C3100 has a switch to charge Lithium cells to 3.7v for storage purpose, now its relativ easy to access.
btw: you lose your warranty.
Print with PLA.
I usedABS couse i had it only in black.
Looks ok but it warped a littlel at the corners.
Model 1 and 3
1x 80x80x15mm 2Pol Fan
Model 2 and 4
1x80x80x25mm 2Pol Fan