Hello there! I upgraded from the 77d to the 90d but didn't have the heart to throw away the third party e17 batteries, after a length of time considering the pros and cons i realize it was as perfectly acceptable risk, at the very least i know it can be done, i would just 3d print it next time if i know how to operate one of those lol, at the very least I'll have two spare backups for absolute emergencies, I'm just a hobbyist and these e6n batteries are expensive, though "cheaper" then their e17 counter parts for some reason. If you know anyone with a similar situation as key then know it can be done lol, probably not practical, but i feel like i saved the planet a tiny bit by not tossing the batteries lol
RE: LP-E17 to LP-E6N adaption