T&T: Subject: Generater running speed

[Dave Clark]

R Barber writes:
"This whole problem of having to run a generator engine at 1800 RPM, or twice
that, in order to maintain 60 cycle current is exactly why I have chosen to go
to a system using a large 24 volt battery bank, a small 1 cylinder diesel DC
genset, and a couple of 3600 watt inverters to supply AC house power.
It is difficult for me to understand how one runs a 4 cylinder diesel at 1800
RPM with little  or no load economically.  There may very well be a direct
relationship between fuel consumption and load, but it seems like that
relationship would break down at light or no load. " <snip>

I agree. Our home on Stuart Island in the PNW is off grid and is wired like
your boat. 20 Golf Cart batteries at 24 volts, two 4000 watt sine wave
inverter/chargers, solar panels, and a back up generator. We use it as if it
were on the grid. Laundry and all. This system is about ten years old and
going strong.

The key, I think, in applying this to a boat is to have a large enough boat
where it will hold a lot of batteries, both dimensionally and the weight of
such a battery bank. Eliminating the larger generator would make up for some
of this. The larger your battery bank in any case the better you are. It
charges faster (less gen time for given amps used), less voltage drop at high
demand (current), and perhaps less susceptible to excessive discharge. Smaller
boats probably could not squeeze it all in and in fact probably do not need
that large of system. They might be better off carrying a Honda 2000.

Arild makes some strong points against the small diesel DC generator. That
coupled with ripping out a perfectly good Westerbeke to make the change keeps
me from converting :-)

Dave Clark
ADAGIO
President 41
Lying Little Current, ON