I am about to finally get a second battery and I was just thinking of how to distinguish between them when I had a thought, why not make them paintable? Obviously there is nothing keeping you from painting a number on a battery, but paint does not adhere well to plastic, but there is a solution. I know many here are outside the US, but fortunately I am not, so I am able to enjoy my other hobby, shooting. Not to long ago a magazine manufacturer, Magpul, came up with a creative solution to allow users to paint a number on a polymer magazine body (to track each magazines round count, identify bad magazines, differentiate them based on contents, or whatever other purpose the user wants to mark them for) that would not chip off with use, they simply added a dimpled area, the paint will stick in the protected dimples allowing markings to stay legible, even if they wore off the ridges. It seems like a simple add on to the battery packs which would allow numbering for convenient at a glance identification. Here is a picture, note the textured area near the bottom of the magazine: Couldn't a simular texture be applied to the back panel of the battery? I guess I could mark the release buttons, but I am not sure it will stay, maybe I should use a sticker, or piece of tape to write on?