Yes, series the two batteries to produce 12 volts. Tap off of the two end terminals for the 12 volts. Tap off of the series jumper for the 6 volts of one of the batteries. The two 6 volt batteries can not be paralleled in this connection as they will short out.
Depends on the battery size. If your boat is a 12 volt system and you wire two 12 volt batteries in series you then have 24 volts. If the batteries are 6 volt batteries you will be fine. If you have a 12 volt system on your boat and want to use two batteries then wire two 12 volt batteries in parallel. You will still have 12 volts but will have double the amperage available and this will extend the running time of the batteries.
12 volts
That is Impossible. You can however make two 6 volt batteries into a 12 volt system by wiring the two 6 volts batteries in Series. You will then have an output voltage of 12 volts but the amperes will only be what one of the batteries have, In other words the volts will double but the amps will stay the same as if you only had 1 battery connected.
600 Volts
Four D batteries in series produce nominally 6 volts (1.5 volts per cell). A 12-volt supply may damage the machine built to run on 6 volts.
No. 12 volts peak to peak would be 6 in the positive polarity and 6 negative polarity. Simply saying 12 volts AC would be 12 volts in each polarity or 24 volts peak to peak
It is 12 volts.
Use a series parallel configuration. Two batteries in series to get the 12 volts. Three parallel banks of two batteries to get an increase of amp hours.
12 volts
The NEMA 6-20R is a 2 pole 3 wire grounding receptacle that is rated for 250 volts. It is not meant to have a neutral wire connected to it. The receptacle is designed to have 240 volts connected to it.
Depends on if you want a series or parallel circuit. In a series circuit if you wire six 12 volt batteries together you will end up with 72 volts. Wire the same six 12 volt batteries together in parallel and you will still have 12 volts. In a parallel circuit you just wire all positive posts together and all negative posts together. In a series circuit you would wire positive to negative to increase the voltage with each battery added.