I think your microwave scenario is an easy one. A good 1750 watt power inverter would do the trick
http://www.outsidesupply.com/index.asp? ... &ProdID=44
Figure 1000 watts to run Microwave
Right at 83.3 amps DC
Then Figure 83.3/.90 for inefficiency in inverter
92.5 Amps
92.5 Amps/ per Hour
92.5 Ah/ 6 ( Since only using 1/6 th of hour)
15.41 Ah per Run
Calculate for increased Drain Rate on Battery
15.41 Ah * 1.3 = 20 Ah
20 Ah is a reasonable figure to use an inverter for.
Microwaves pull alot of power, the beauty is that no one wants to cook in them for 30 minutes or an hour.
More fast food options.
Also make sure the continous rating of the inverter is at least 1500 watts.
Get an inverter too small and they kinda brown out when running microwaves.
Also not the new fast cook microwaves require true sine wave inverters for the most part.
We also sell auto isolator switches to allow vehicle to charge 2nd battery but not allow for devices behind 2nd battery to drain start battery.
