Disregarding the possible merits of the idea, the problem is going to be
matching the alternator output to the inverter. The inverter expects to
see 12 VDC (nominal) but could be designed (could have been designed) to
accept the multi-phase, higher-voltage, frequency-dependent-upon-engine
speed, alternator output.

Your job, should you agree to accept it, is to query the inverter
manufacturers to determine whether their products will accept
unprocessed alternator output. Having established that such units are
commercially available, we can then debate whether the arrangement is a
"good idea".

By way of a preview, depending on an awful lot of awful things, your
Model T-era charging may not be improved much by even the most costly
charger on the market. You might try to establish whether it is the
alternator/regulator combination that is causing your charging
irritation or the unwillingness of your expensive AGM's to accept bulk
charge at the exalted rates of which we dream.

Chuck



Roger Long wrote:
Here’s one of those wild ideas that will probably get shot down
(probably by Larry) but some of us may learn something from the
patterns the flames make.

I’ve got a nice, temperature compensated, battery charger for running
off the AC at dockside. When running for long periods under power
however, my expensive AGM’s are being driven by the alternator which
isn’t significantly different from the ones on the Model T.
Retrofitting my larger spare with an expensive, 3 stage, temperature
compensated regulator is on my wish list.

However, why not disconnect the alternator from the battery circuit
and run it to an inverter large enough to run the dual 10 amp battery
charger? The battery charger then plugs into the AC and one charger
does it all. If I switched off the battery charger, this would also
give me some AC power when the engine was running.

I don’t use AC much and don’t care much for making it by drawing down
my batteries. I wouldn’t mind having the engine idling for the
infrequent times I would like AC away from the dock.

If I could make this work (by switching off battery charging) well
enough to heat up my small hot water heater, which would also be
getting waste exhaust heat (although not much with just 20 HP) , it
would be the nuts.