Are Batteries a/C or D/C?

All batteries use DC, not AC. Realizing AC batteries expands more flexibility, especially when combining with the Cockcroft-Walton Multiplier, [a circuit that generates DC voltage from an input of alternating current].

Are 12 volt batteries AC or DC?

There are both DC (direct current as from 12 volt batteries) and AC (alternating current like what you use in your house) systems and issues on many boats, although some boats, particularly smaller ones, only use DC. Here we'll discuss primarily DC.

Is battery operated DC or AC?

Batteries and electronic devices like TVs, computers and DVD players use DC electricity - once an AC current enters a device, it's converted to DC. A typical battery supplies around 1.5 volts of DC.