Fridge and Microwave Watts (and Solar) - RV-Dreams Community Forum

The Hensons · RV-Dreams Family Member

Fridge and Microwave Watts (and Solar)

bjoyce · RV-Dreams Family Member

Batteries under load can go into the low 11s, your cutoff is too high by about one volt. Or you need more batteries. If you have four golf carts and load them with 2100 watts you will drop the voltage into the low 11s and, if they are weak, into the 10s.

Lonney Wade · RV-Dreams Family Member

Ok, time to ask some questions.
Do you know the size of your battery to battery cables and battery to inverter cables.
I have a 3000 watt sine wave inverter and the cutoff is 10.5 volts, you have your cutoff to high as bjoyce has said.
All your cables need to be at lease 2/0 in size, if they are smaller your voltage will drop and the cables will become warm to hot and that is where your voltage drop is coming from.
I did a 1 hour test in 2 stages, first test I turned the fridge on, like yours a Dometic RM1350 with a kill-a-watt meter was pulling 400 watts then I turned on the air conditioner 1920 watts all on the inverter with (420 Ah) of AGM 12 volt batteries for about 10 minutes, batteries under load went down to 12.3 volts.
I fired up the charger and put a amp meter on the cable by the batteries, was pulling 284 amps, within a minute it started going down in amps and leveled out at 118 amps and stayed there, the motor went from heavy load 3000rpms to light load about 1500 rpms.
Second test same as the first but with the truck with 2 alternators cables in the bed 2/0 in size, batteries was taking in about 200 amps, no sweat for the truck.
I know, I know I do a lot of testing, boring.
That is my story and I'm sticking to it.
I hope this has helped you out some.

Lonney
I

The Hensons · RV-Dreams Family Member

Thanks for the input...

Yes, I suspected my cutoff was too low...I had a Magnum tech tell me as low as 11.0v is okay. 10.5 would make me nervous though!

I've got some pretty hefty cables...1/0 connecting my two battery banks (4 brand new Lifeline AGM GPL 4CT) together and 1/0 connecting batteries to inverter as well.

But, that still does not explain the wattage on these appliances. I tested them in isolation: I took an extension chord from the appliance itself out to the shore power where I had a meter plugged in. That's where I got those crazy high watts.

01zeosix · RV-Dreams Family Member

The Hensons wrote:
Dometic RM1350: 450 watts!
GE Profile Micro/Convect: 1670 watts!
Does that seem right? Residential fridges are about 1/4 of that aren't they? Microwaves are about 1/2 that, yes?

Dometic RM1350:
Your RM1350 can and will run as high as 450 watts. Are you switching the unit from "Auto" to LP when you are running off the inverter? Will help you save.

GE Profile Micro/Convect:
1000 watts under Microwave and 1600 watts under convection are "normal".

Magnum Hybrid:
I would suggest that you contact Magnum Tech Support to review the settings on your inverter. I have the same setup with 4 AGM batteries and don't experience the cut-out issue you describe. You can ping me offline and I'll be more than happy to share my settings with you.

Sounds like your never reaching a state of "Float Charging" on your Magnum. It takes mine about 3 to 4 hours of FULL sun for mine to come back to float on its own (solar). There are also times when I have to augment with my generator in order to reach float.

Of course energy management is very important. You have +-440 Amp hours of battery available in your bank. It would be helpful to know what solar controller, panels, wiring from panels to controller, etc.... you have and also, whether or not, you have a generator to help with daily replenishment of your energy system.

Purchase a "Kill-O-Watt" meter to help you analyze your energy usage. Lots you can do to help conserve. Turn off what you don't need. Use surge strips where practical to help with the "phantom" loads. Consider LED lights. Yadda Yadda...

Lots of good information on this (and other) forums. Again, ping Magnum support (or contact me offline) to review your Inverter settings. I really like mine.

Hope this helps some...

bjoyce · RV-Dreams Family Member

This "meter plugged in" is what model? Most of us use a Kill-A-Watt or equivalent. I prefer the Floureon TS-836A, $16 from Amazon, since it keeps track of maximums. The numbers might not be crazy high, my residential fridge uses more power than I expected when it decides to defrost or make ice. 4 4CTs is a little light for a 3000 watt inverter, I would want 6 of them.

The Junkman · RV-Dreams Family Member

Added a Floureon TS-836A to my amazon cart ! thx

The Hensons · RV-Dreams Family Member

Thanks 01zeosix and bjoyce!

I'm getting the 1670 watt reading on (30 sec. quick cook) the microwave, not the convection. The convection is even higher. My fridge is staying at 450 watts. I really think there is an issue in these appliances. I suspect something has damaged them.

I've lowered my cutout on the Magnum so hopefully that will help.

I actually am reaching float with no problem...I think it took time for the batteries to 'learn' the system a bit. I've only had it for a few days.

01zeosix asked about some of my equipment. Here is what I have:

Magnum hybrid 3000
Blue Sky 3024il MPPT solar charge controller (Greg @ AM Solar suggested this since I told him I intend to go lithium in 3-5 years) with shunt kit and temp compensation
All of my wiring is either 1/0 or 2/0 (heavy!), except the wiring connecting 2 6v batteries in series.
Onan 5500 lp gen
4 x S-GO 160 watt panels connected to Magnum roof combiner box
I am using a subpanel

Thanks for the tips! I'll get a kill o watt. I don't know what the Magnum tech was using to read those watts. But I'm sure his readings are accurate because they are confirmed by the inverter readings (amps x volts = watts)

01zeosix wrote:

Your RM1350 can and will run as high as 450 watts. Are you switching the unit from "Auto" to LP when you are running off the inverter? Will help you save.

GE Profile Micro/Convect:
1000 watts under Microwave and 1600 watts under convection are "normal".

Magnum Hybrid:
I would suggest that you contact Magnum Tech Support to review the settings on your inverter. I have the same setup with 4 AGM batteries and don't experience the cut-out issue you describe. You can ping me offline and I'll be more than happy to share my settings with you.

Sounds like your never reaching a state of "Float Charging" on your Magnum. It takes mine about 3 to 4 hours of FULL sun for mine to come back to float on its own (solar). There are also times when I have to augment with my generator in order to reach float.

Of course energy management is very important. You have +-440 Amp hours of battery available in your bank. It would be helpful to know what solar controller, panels, wiring from panels to controller, etc.... you have and also, whether or not, you have a generator to help with daily replenishment of your energy system.

Purchase a "Kill-O-Watt" meter to help you analyze your energy usage. Lots you can do to help conserve. Turn off what you don't need. Use surge strips where practical to help with the "phantom" loads. Consider LED lights. Yadda Yadda...

Lots of good information on this (and other) forums. Again, ping Magnum support (or contact me offline) to review your Inverter settings. I really like mine.

Hope this helps some...

bjoyce · RV-Dreams Family Member

I don't know anyone who runs their RV fridge on electric when boondocking. They are pigs. Our old 12cu ft Norcold had over an 80% duty cycle, so it seemed it was always running. We once had the RV in a repair shop, where we thought it was going to be plugged in so we did not shut off the inverter the Norcold was hooked to. We used over 300 AH during the day, a full 24 hours would have been 900 AH. Run it on LP!!! A residential fridge uses much less electricity, approximately 100 AH for a full 24 hours, give or take.

-- Edited by bjoyce on Friday 20th of June 2014 09:07:22 AM

The Hensons · RV-Dreams Family Member

900AH...yikes!

I expect to run on LP as well...but I'd just like to be able to run on electric if I run out of LP. I've played with my settings and feel I've got things optimized now. I still don't see me using my microwave/convection on solar though. At least not with my current set up.

The park we are staying at now offered a $175 cheaper month rate if we went on metered electric. I gladly accepted :) I'm already loving the solar.