On Sat, 6 Oct 2012 23:51:42 -0400, "Existential Angst"
wrote:

Awl --

In discussing using inverters+car alternator as a backup power supply, and
observing some hefty cobra 5,000 W inverters ($310, google shopping), I was
wondering if these can be made even heftier with stock parts? I wonder if
these large ratings in cobra units aren't like Sears hp....

It seems like the bottleneck in this strategy as a house backup power supply
is the car alternator. 5,000 W would require about a 500 Amp alternator!
But mebbe a regular car alternator + a bank of batteries could handle all
the peak loads/draws, as long as they didn't last forever. Anyone here ever
do this?

Not particularly uncommon in yachts. Usually to power an AC fridge. It
works. Measure the actual amperage used by the fridge connected to AC
and then amp and volts required by the inverter powering only the
fridge and you get a good idea of the efficiency of the inverter. As
for sizing the inverter most people use a factor of 2, you need 1KW
buy a 2 KW inverter.

Gensets, even nat gas ones, seem to be a real pita, and the noise is
considerable, unless you get real pricey.

Insulated generator enclosure and efficient exhaust system.
--
Cheers,
John B.