Oh, I see now -- you are going to use it while the engine is running.  I
was thinking you were just going to use it for camping.  You don't say what
the continious current draw of the air conditioner is.  If we assume it is
4 amps and you had a 40 amp-hour marine battery, you would get 10 hours.
Of course, the occasional 6 amp peaks when the compressor kicks on and the
inefficiencies of the inverter might reduce that some.  So even if you only
get 8 hours, this isn't sounding so insane after all!

If you are running it while driving, then I guess watch for premature
failure of your alternator, since it has to work harder.  Where are you
mounting this thing anyway?  You can't hang it from the front window while
driving!

Michael

> I dunno about that -- peak 6 amps/690watts? on a 1300-watt surge/800-watt
> continuous, 15-amp inverter?  You could be right of course; I'm just
> spouting numbers from the design docs and don't know what they mean. My
job
> is to supply the Westy, beer, and band-aids. And fire extinguishers.
>
> And though I come off as a moron on purpose (because I am!), we've
actually
> set this up outside the van on a borrowed inverter and it works well (so
> far, anyway). The a/c compressor won't need to engage very often (I'm not
> planning on crossing a desert), so the charging cycle so far has kept the
> battery in good shape over several hours so far. We'll run longer tests
this
> weekend.
>
> ~ JR