Hi
Just spotted this thread, so I am answering all posts on the way through.
1. Invertors draw .7 Amp minimum even when doing nothing
2. A 700w Microwave will use around 1050w Input to run, this isnt start up Wattage, 700w Refers to the cooking output only it needs 1050 to make 700w Output
3. Running the microwave on low will not help, it cycles on and off, therefore its still running 1050w most of the time.
Here is something I wrote way back to help people understand Microwaves and Invertors
http://s7.invisionfree.com/UKSB/index.php?showtopic=29
Never ever use a suicide lead, even if you think you will always remember to plug the off side in first before it becomes live you (or someone else) may forget one day. This is especially dangerous because;
GFCI these will not work with an Invertor because invertors have no earth, this means there is no earth for any current to leak to ergo GFCI as no reference and will not operate, this means that the only way to get a shock is a direct short between the live and return pins (which on a suicide lead exposes both) Direct shorts are the most unlikely kind of electrocution.
You can run a mains fridge via invertor, but you need a fair few batteries to wild camp (I have 10 X110 Ah batteries) Its also ok if you always intend to use shore power, you can power via invertor on way (which is powered by engine alternator)
Running computers via Modified sine wave, many people (over here) including me have done it no problems at all and not suffered any adverse effects.
There are only a few things that wont work on Modified
1. Washing machines they have thyristor control
2. Power tools with thyristor speed control, try it it will either work or not
3. Electric toothbrush chargers, do not try it ever it will destroy the charger
4. Dual sets ie TV/DVD and TV/VCR many have these have thyristor's in the twin power supplies internally BUT do try it many also work no problems at all.
Always use big thick cables and site your invertor close to the batteries. voltage drop is not really a problem out the mains side, but its a serious issue on the12v Side.
In the last few posts its been mentioned about the drain when not in use, I guarantee its .7 or above. but I have noticed several people reccomending using a meter and some confusion about what actually to measure 240v? etc, If you have no idea do not go messing with a meter and battery, scrapping a meter is the least of your worries, serious injury could result.
Just for the record you need to measure ampage, most modern meters will check up to 10 Amps without a shunt. if you dont get it do not try.
Have fun