Newsgroups: misc.emerg-services sci.electronics.design misc.consumers.house
Subject: Re: how best to get electricity for emergency prepareness
From: nospam 
Date: Tue, 20 Sep 2005 03:06:50 GMT

1. Crunch the numbers; a separate car battery doesn't store
enough energy to run an inverter for very long.  Also,
inverters tend to shut off if the input voltage falls below,
say, 10V.  That protects the battery from discharging, but
prevents the inverter running off only a battery for long.

2. Only obsolete inverters produce a square wave.  The current
technology gives a modified sine.

3. The starting current that motors draw is a real issue.
The inverters I was reading up on yesterday claimed that they
could supply a starting current twice their continuous
current.   However, I wondered if that was conditional on
enough DC current being available w/o drawing down the supply
voltage too much.

4. I was unable to run a stand-up freezer on a 700W inverter,
even using a large gauge extension cord, with the car running,
and revving the engine.  I haven't tried to power a fridge
yet.