For pinch hitters in the event of a disaster. I found a convenient item called "Battery Changer" at Daiso, a 100-yen shop.
A case for changing the size of AA batteries. By inserting the battery and closing the lid, it can be used as a C1 or CA battery. It seems to be useful for a pinch such as "If you try to use a flashlight because of a power outage, the AA battery inside is dead!" There are some points to note, and it is NG to use or store the device for a long time. In addition, it seems that it cannot be used in combination with a regular battery because it may generate heat or leak.
According to the "+" and "-" at both ends,
Transform into a single battery!
This is also true for C batteries
It's just an emergency measure, but it's a "battery changer" that helps in case of emergency. How about adding it to your home equipment as disaster prevention goods? The price is 108 yen for 2 models that convert from "AA to AA" (tax included, same below), and 108 yen for 3 models that convert from "AA to AA".