All About Batteries Video

"A", "B" and (at one time) "C" batteries are classes of batteries for vacuum tubes, rather than a specific type or size

"A" type batteries came in many sizes and operate the vacuum tube filaments, many times 1 1/2V as well as 6V
"B" batteries were the high voltage batteries for the tube anode or plate
"C" batteries were the negative "bias" voltage for the tube control grid, not always used.

At one time I had a big console radio "farm set" battery that was combined all in one. I forgot, either 90 or 105V "B" battery

The 1 1/2 "A" section had 4 of the big "telephone" dry cells taped up in the wrapper, and the B and C sections were made of little rectangular wafer cells similar to a 9V if you have ever torn one of those apart

B voltages were things like 22 1/2V, 45V, 67 1/2V, 90V, 105V I've forgotten what else

A few more:
Vintage Radio Batteries
batteries.jpg