Batteries for old Radios for the new tech.

A Battery: Filament battery. No set voltage. The majority were 1.5V, 3V, 6V

B Battery; Supplied B+ to the radio.  Typically 45V, 67V, 90V and 135V

C Battery: Bias for the radio. Often 4.5V but can be 22V or another odd voltage.

Some radios used what is called an 'Acorn" battery for bias.  Basically because they really resembled an acorn. Typically 1.5V. Strange looking battery and the holder looks like a very oddly shaped snap type C Clamp. Basically unobtanium any more,  But-- Sometimes you can "restore" the battery by injecting water into it. Now this battery generally only provided a couple of MA at the most. 
  IIRC There were some old Mercury batteries used for photography that used the acorn cells in them. I discovered that back in the late 60's. No idea if that type of battery is even made anymore.

Now very often the B & C batteries were combined into one battery and even the A, B, and C batteries into one brick shaped battery.
 In hi current draw radios where the filament drew a lot co current they used a cylinder shaped "A" battery, typically 1.5V.
 I have seen some radios use wet cells for the filament also. 2V Willard batteries & 6V car batteries. (The 6V batteries were placed in the bottom of the cabinet with large crocodile clips to connect to the battery so you could take it out & recharge it from the car)  

On any radio that used wet cells, especially the 6V car batteries, check the bottom shelf of the radio for "punkyness or spongy" wood. The battery acid can do a lot of damage to the wood. This was often the cae when the home owner got AC tot he house and used a Tungar bulb/Recticon bulb type charger. The battery could spew out acid while charging and it deteriorated the cabinet wood.
( I have a Knight console radio that the bottom shelf of the cabinet feels like spongy balsa wood that has no strength left.)