On Fri, 18 Jul 2003 10:24:24 -0700, "David Oswald"
wrote:
Unless you have a lot of battery capacity, your inverter will pretty much be
limited to supplying power to small loads. If you've got a couple of Group
27's, for example, pair them up with a 300w inverter that will power your
laptop, your blender, and the electric drill.

Larger capacity battery banks can effectively supply power to larger
inverters. But consider the load you're putting on the batteries. If
you've got a 1500W inverter, and you're running full capacity through it,
you're drawing your batteries down at a rate of nearly 140 Amps (assuming
90% efficiency). You would completely depleat (and destroy) a pair of
Group27 batteries in about 90 minutes. ...probably sooner actually since
they're really not designed to supply that kind of load over a sustained
period.

Even a larger battery bank of 450AH is only going to last about 1.5 hours at
full inverter load (with a 1500W inverter) before it's at 50% charge state,
which is as low as you should take it.

Inverters are useful for low consumption long term loads (such as a
notebook), or for moderate consumption brief loads (such as a drill or
blender). If your battery bank is large enough, inverters are even ok for
high-load short-term use (such as a microwave).

But if you need prolonged power, such as supplying power to an electric
heater, electric cook-top, full-size TV, DVD and Stereo, or an Air
Conditioner, you're going to have to run a generator.
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All of that is true but there are many uses for a high wattage
inverter never the less. A microwave oven, blender, vacuum cleaner,
one burner stove top, are all uses that my 440 amp-hour battery bank
cheerfully supply power to over periods of 3 to 15 minutes. I've even
been known to turn on the hot water heater for 15 or 20 minutes if I
want an eary morning shower with out running the generator. The
secret is to monitor your batteries, not draw them down to less than
50% of capacity, and recharge promptly with the generator when
convenient. Large battery capacity is key, as well as properly sized
cables between battery bank and inverter.

In my view the best use of a high power inverter is as a supplement to
the generator, not as a replacement.