Check out this tip on using a 9 volt battery for AAA use. I have seen where they say you can open one of those big square batteries and find it just stuffed with double A batteries but then I have seen a couple of them torn open only to find some weird type of battery cells in there that you couln’t use for anything but this one looks like maybe it would really have these bitty batteries that you could put to use in them. See the video from Sensible Prepper.