XT-60 Battery Plug Cover

thingiverse

I use stickers on the end of a discharged battery to keep track of which ones need to be recharged when I get home. Red is an obvious choice for this purpose, given my concern about accidentally charging a drained battery. A friend suggested using green stickers for fully charged batteries and it achieves the same result. No adhesive-backed supports are needed; instead, the design ensures a snug fit so they don't come loose.