In article , Chuck Cox
wrote:

Yes, this is an old thread coming back to life...

Back in December I wrote:
As part of a non-boating-related product, my company is designing what
amounts to an automatic 500w DC self-starting gasoline battery charger.
The charger is designed to be portable, unobtrusive and easy to
maintain. If the battery has sufficient charge, it can self-start, but
it can also be hand-started easily when necessary. It is designed to
automatically start and stop as necessary to keep a battery charged.

Having read postings here about cruisers running with reduced radar and
lighting at night in order to conserve battery power, it occured to me
that we could repackage the charger for marine use. It would be roughly
shoe-box sized and effectively silent unless you were sitting next to it
on a calm day. It seems like this would be useful for boats with no
genset and modest electrical loads (i.e. lights & electronics). When
connected to the battery it would automatically start up and and shut
down as necessary to maintain the charge. It could also be designed to
cooperate with external charge controllers.

It seems like it would be a useful product, but I found nothing like it
when I googled for obvious keywords. Does such a product already exist?
Would there be any interest in such a charger? I know I have been in
situations where it would have been useful.

Roger Long and several others then made very convincing arguments that
diesel would be the best fuel for this product. Well, my partner has
found an appropriate diesel motor and electric motor/generator. We are
putting together a test stand now and should get some real-world data
soon. My partner insists that lubrication is not a problem at any angle
of heel, but that is one thing we'll be taking a hard look at.

There are a couple of major variables that I'm still unclear on: how it
will get fuel and where it will be located. For fuel, I'm wondering if
it would be preferable to have its own fuel tank or to connect to the
main fuel system. For location, it could be a stand-alone unit that you
put on deck to operate, or a built-in unit that could operate without
getting in the way. Clearly these two issues are inter-related.

My original idea was to make it stand-alone with its own fuel tank. By
using a small fuel pump, we can locate the fuel tank beside the motor
instead of on top like most generators. This would make for a
low-profile package that would be less intrusive than a typical
generator, but you'd still have one more thing on deck to trip over.

So, if you were to put such a system on your boat, what would you prefer?

Depends. Is this going to be water cooled or air cooled? If water
cooled, sea water or fresh water with radiator or via heat exchanger?

I'm assuming air cooled as this is simplest for an engine. However, it
may be noisy and need access to ventilation so belowdecks may not be
ideal.

My preference would be for an integral tank that gravity-feeds the
engine. This is simplest and therefore cheapest. You can always use it
as a day tank and fill via dedicated line from the main tank, or rig up
a float switch to kick in a pump.

I too think this is a good idea and if the price was right, would buy
one. We built something similar to use on an island once, but it was
petrol powered and quite noisy, plus relatively inefficient. Used a
motorcycle permanent magnet alternator.

PDW