One of the best improvements the military has made in the last 30 years...standardizing on batteries.
It used to be that the military would buy a new gizmo....which was powered by some unique battery. The manufacturers would claim it was for technical reasons, but in reality it was to ensure a continuous revenue stream for them (since they were the only supplier for that battery).
We used to have PRC-91 survival radios in aircraft survival kits, which used a different battery than the SDU-5E survival strobe light, which used a different battery than the URT-33 seat beacon....all different, all big, all heavy so we couldn't carry spares for them.
Now mostly all AA's, a darned good thing. But it's getting to the point where an infantryman is carrying more weight in batteries for a 3 day patrol than ammunition.