House batteries to use with large inverter

We use our 4 GC batteries (484 AH) and a Xantrex Prosine 2.0 pure sinewave inverter with our micro-convection oven regularly. It pulls about 150-160 Amps from the batteries, (75-80A each) Cables are 4/0 about 3 feet long.

For those thinking about purchasing a microwave for use with an inverter, consider a microwave that uses inverter technology for power control such as Panasonic and GE. (Note that the inverter of an Inverter Microwave oven has nothing to do with running it from batteries via an inverter. The inverter technology in those microwaves use an inverter to control the power level. For example, an inverter microwave oven at 50% power really only draws half of the full power while running. An NON inverter microwave oven at 50% power level draws 100% power but for half the time. The first method is much better for the batteries.

pianotuna wrote:
What do you plan to reheat? If your times are 5 minutes and under a small battery bank can do the deed.

It's mostly five minute type operations, a couple of times each day, to be replenished by generator. The places we're thinking about allow generator use twice or three times each day, so recharging shouldn't be a concern. If I were trying to recharge with solar alone it would be a different story.

Secondary is when we have the RV serviced, it can be a few days before we get it back, so I want to be sure the propane fridge will keep going. That should be very minimal, but with my current batteries, a week of fridge and other small loads was enough to kill the batteries.

The space I have to work with is about 19 inches wide, 14 inches deep, and 12 inches high. I don't think I can get four batteries in there, but I think I have room for a couple of size 31 batteries. I saw some from Fullriver that claim 45 minutes at 75 amps, 115 AH with smaller loads. Not very long, but I was glad to see it even mentioned that they could deliver 75 amps.

Now I have to measure the voltage produced by my converter, to see which batteries I can use.

RGM will work great with the microwave. I have a MSW Trace and I use it a lot to prepare fish and frozen vegetables. With the fish it's 8.5 minutes instead of five four minutes to reheat a large mug of coffee instead of two minutes. There's few PITAs more intense than "Ooops if I do this then I can't do that" decision. Get as many amp hours as it takes to make your life comfortable. AGM batteries have that wonderful high wattage capability that inverters/microwaves love. Sounds like you are on the right track.

What do you plan to reheat? If your times are 5 minutes and under a small battery bank can do the deed.

If on the other hand you wish to reheat a frozen meat loaf (precooked) that takes 20 to 30 minutes, then you are going to need a pretty massive bank.

Order of preference for running large loads for long periods of time:

AGM 12 volt
AGM 6 volt
Flooded 12 volt marine
Flooded 12 volt deep cycle
Flooded 6 volt golf cart type.

Remember--every 10 amps you take out of the bank has to be replaced by 11.

My microwave is 1591 watts so it draws 160 amps. In theory I could run it from my medium size battery bank for about 30 minutes and only use up 20%. About 112 amp-hours. That's about two days of solar harvest for me under ideal conditions.

The MW is similar to starting a motor in that it is like an inductive load instead of a resistive load which is easier to run. So you want in inverter that is rated to run motors to run the MW.

Unicorn1108 wrote:
is running the microwave similar to starting an engine?

No. Starting an engine is a few seconds affair. Running MW is (at least) a few minutes at a time, and current is usually higher than with engine starter. You need deep cycle batteries, preferably +250 AH capacity @12V. In other words - 4 or 6 of them. 150A is too high current for 2 batts, will probably run but not a good idea.

Dual purpose - what they usually write on cheap batts from Walmart and so-called marine batteries - would also work, if this is what you have. Boaters are doing it all the time. I prefer starter battery for starting, and deep cycle for coach.

There are some low-volume MW with max current around 100, but in RV they always put big MW with high current - and not expensive inverter MW either. Just big and cheap.

Ain't to see if the food's done. It's to compare.

Battery heat up

Inverter heat up

Microwave magnetron heat up

But food no heat up

Grand Energy Plan Go Bang!

Ampere hours versus temperature. Cook spud in campfire. Foil wrap with three teaspoons of water No square wave round hole issue.

MEXICOWANDERER wrote:
Remember my glass of water
Microwave temperature versus time
Comparisons. You can do the same with different batteries, MSW vs PSW
And the thermometer is right before your very eyes.
BS Proof

Mex that is correct, but when all you do to decide if the potato is ready is stick a knife in it to see if it is soft enough, then your times don't matter so much.

How warm is enough to heat up left-overs? So you can get away with less time on MSW except if you have a strict target like boiling water, that is either boiling or not.

Anyway I use an electric kettle for that, not the MW, and the kettle doesn't care if it is MSW or PSW :)

I think the inverter is pure sine wave, so I'll go by the 150A figure, and try to find a pair of 12V AGMs that can handle it. I'd rather lose the MW than lose the TV, so my priority is probably total AH more than MW performance.