YES, a second battery bank is needed!!
You will need a Perko a/b switch like this one:
This allows for 2 battery set ups. Typically, position 1 is the starting battery and position 2 is for the amps battery(s). The switch is used to point to the charging system(alternator) to either battery or both while the engine is running and also determines which battery will do the starting. Some people also incorporate the use an isolator that will determine which batteries get the alternator charge like this:
I use 2 golf carts batteries for my second battery bank, see the discussion topic POWER.
Wiring all depends on how many batteries you will use.