[Cobaltblue]

I guess your looking at this picture you can see 3 Batteries

The Big one is the HT (in Red) these often had multiple taps making them suitable for many different sets and valve types.

The Blue one is the Grid Bias it looks as if this has two taps in use.

Lastly the green is the LT accumulator usually a Gel type in portable sets.

Cheers

Mike T