They usually have an on/off switch, as they do have marginal consumption
when unused.
Power consumption is dictated by what is connected to the
Inverter, however, they are not %100 efficient, and a larger inverter may
have more static overhead.
I have a yellow top optima, only one of them, I can watch a couple of DVD's,
charge the laptop, and cell phones, and a camcorder, run my fluorescent
light and still have ample to crank the engine. The first time I tried this,
I parked on a hill though, just in case.
Best of luck to you, I have never been able to drain my single Optima
yellow.

Jerry

Considering adding an inverter to the dual battery setup in my '88
Westy. I have my eye on the Coleman Powermate 800. I have a couple of
general questions:

1.) Is an inverter on all the time if connected to my second battery,
or do they generally have an on/off switch? The concern here is that
if it's on all the time, the inverter's cooling fan (if any) might
come on intermittently during the night when I'm trying to sleep.

2.) Power consumption is dictated solely by what is connected to the
inverter, and not the wattage of the inverter itself, correct? IOW, a
Powermate 1200 won't drain my battery any faster than a Powermate 800
if they each had the same items attached to them, correct?

3.) Any problems/issues with permanently mounting an inverter to
either side of the stove? Seems like that would be an ideal place to
plug in the laptop, cell phone, etc.

4.) Finally, would the secondary battery (Optima deep-cycle marine)
last long enough, assuming fully charged, to watch a long-ish (say, 3
hour) DVD?

Thanks for any help,
Chris
'88 Westy, "Rocinante"