--- In electricboats@yahoogroups.com, John Francis <surv69@...> wrote:
>
> Why is it necessarily better to consider 12-48 volt motors DC, when the use
> of a 120 volt AC motor would allow all the 12 volt batteries to remain just
> that . . . 12 volts? The charging system would always be 12 volts and the
> addition of odd-number batteries would never be a concern(?).
>
> A person could begin with the minimal available power and piecemeal
> additional power, sorta . . . on the fly, cause the deliverable power will
> always be 120 volts AC.
>
> Is this a realistic way of considering electrifying?
>
> John Francis
> Port Clinton, Ohio
> Pearson26 (hopefully, soon to be a Pearson 30 with a removed engine)
>
>
Hi John from a fellow Ohioan,
The answer to your question has to do with current (amps). For DC, you get power by multiplying volts times amps. If the voltage is too high, things get dangerous. If the current is too high, you need huge wiring and expensive switches. So, it is always a tradeoff. I think you assume that AC is easy to come by on a boat - just get an inverter. However, the same tradeoffs apply. To get 10,000 watts out of an inverter that runs from a 12 volt battery, the inverter would be drawing at least 833 amps out of the battery! That is a huge amount of current. By the way, in real life, the number would be even higher since inverters are not 100% efficient. If you use a 48 volt system, you cut the current to 25% of the current in a 12 volt system. Does that help?
Pat
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