So I did run this test and learned a few things:
-my 1000w microwave is only running at about 800 watts. I am guessing this is due to the fact that Im using an $80 1200 watt max MSW inverter to run it. It still heats and runs fine and I boiled the cup of water in a few minutes. I didnt realize that it was running at reduced power until I did this test. This is the inverter: https://www.amazon.com/gp/product/B075ZPMJZH/ref=ppx_od_dt_b_asin_title_s00?ie=UTF8&psc=1
-My voltage dropped to about 11.2 v after running the MWO (Microwave Oven) for a few minutes. At first glance and from @HarryN s posts this sounds like a major issue but while MWO was running I turned on my compressor fridge which draws 5 amps and my propex furnace which draws 2 amps and they all ran happily at the same time. So I looked up what the cutoff voltages actually are for these devices. I checked the manual for the isotherm fridge I have and it does not cut out until it gets down to 10.9 volts. I also have a webasto chest freezer, it doesnt shutoff until voltage drops to 11.1 volts and that is on the highest setting. The propex manual says it does not shut off until voltage drops below 10v. Manuals for reference below:
Test was performed on a cold morning with overnite temps in the 20s and interior temp of the van in the mid 30s at the time of the test. Battery is a 100ah interstate AGM mounted under drivers seat on its side. Battery purchased and installed in 2017, it is 4 years old and has been used and abused in extreme temperatures during that time, primarily I use the van for skiing in Colorado, many, many camping trips with overnite temps below 0f.
After 5 min of testing, battery SOC was about 92%, I turned on engine and got about 50 amps from alternator which quickly dropped to 40-30 amps. Screenshots from victron battery monitor below.
My conclusions from the test:
- @HarryN is right that voltage does drop below 12v with high amp draw from a smaller capacity system like mine (single 100ah AGM).
- @HarryN is mistaken that a majority of fuel heaters or compressor fridges will turn off when voltage falls below 12v. Maybe there are 12v appliances that dont operate below 12v, curious to know what these are if they do not include compressor fridges/furnaces?
- real world experience running fridge/furnace/MWO and other loads simultaneously is that the voltage drop is a non-issue for MY real world use. After 4 years of use I did not even notice voltage drop while simultaneously use MWO/Fridge/Furnace because I have never experienced a low voltage shutoff.
Running all 3 devices (MWO, furnace, fridge):
Charging immediately after test:
