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Old 07-15-2021, 09:08 AM   #1
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Question 12 Volt Refrigerator Run Time on Battery

We have a new 2021 Leprechaun Motorhome. This past weekend I tried to run the 12 volt refrigerator on battery (our refrigerator is only 12 volt, no propane, no 120 volt). Got home Tuesday night, leveled up, did not connect shore power, left refrigerator running since it was late. 10:30 at night the motorhome engine was shut off, refrigerator left on, running off battery. 3:00 the next afternoon, both my deep cycle batteries were pretty much depleted. It was not too warm ODT low 80s during the day, upper 60s during the evening. How long should I be able to run the 12 volt refrigerator off of 2 100Amh deep cycle batteries?
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Old 07-15-2021, 09:23 AM   #2
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Assuming your two deep cycles were fully charged and there were no other 12vDC electrical loads you've posted the answer to your question. 17 hours.

To confirm put the unit back on shore power for at least 24 hours and repeat the test.

The data plate inside the refrigerator will show the power draw in watts and amps. Looks about 17 hours at 6 amps will suck over 100 amphours from the battery and it'll be down to 50% power and about 12.0v which may not power the inverter. 12v systems are really 12.7v at 100% capacity.

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Old 07-15-2021, 10:11 AM   #3
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Great information! Worst case, likely you are good for 18 hours.

There are tricks to improve the fridge. Always full! Never add warm stuff. Keep the doors closed.

The weather makes a difference.

You need more battery or a lot of solar. Two lithium batteries would double your time. 800 watts of solar would help! No more generator. A battery monitor is a good plan.

Run the generator as needed.

This is the direction the market appears to be taking.
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Old 07-15-2021, 10:22 AM   #4
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As we speak I am running a test on my own GE 12V refrigerator and single stock Xpedition "100 Ah" battery. Based on experience and some previous preliminary testing, however, I seriously question whether I'll be able to get 50 usable Ah out of it -- hence the quotes.

I started the test at 9AM today with the RV in my driveway. Shore power had brought the battery to a full charge and the refrigerator to 34F. I disconnected shore power and began recording hourly battery voltage and state of charge readings as reported by a Victron SmartShunt. I also am recording hourly refrigerator temperatures. The SmartShunt also records historical cumulative power consumption.

I will stop the test when voltage reaches 12.0 and/or SOC reaches 50%, or bedtime tonight, whichever comes first.

I plan to write up the results and post them in a new thread. I will add a link to it in this thread if you're interested.
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Old 07-15-2021, 11:03 AM   #5
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Interested.

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Old 07-15-2021, 11:08 AM   #6
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Quote:
Originally Posted by Lepre 21 View Post
We have a new 2021 Leprechaun Motorhome. This past weekend I tried to run the 12 volt refrigerator on battery (our refrigerator is only 12 volt, no propane, no 120 volt). Got home Tuesday night, leveled up, did not connect shore power, left refrigerator running since it was late. 10:30 at night the motorhome engine was shut off, refrigerator left on, running off battery. 3:00 the next afternoon, both my deep cycle batteries were pretty much depleted. It was not too warm ODT low 80s during the day, upper 60s during the evening. How long should I be able to run the 12 volt refrigerator off of 2 100Amh deep cycle batteries?
How long you ask?
Apparently not as long as you did.
I donít know the real answer, because no two batteries are in the same condition all the time.
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Old 07-15-2021, 12:23 PM   #7
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Run Time

What I can't figure out is WHY does the fridge draw so much power?

The cooling is via propane and as far as I can see, you have a thermostat and a sparker than comes on once in a while.

Does the valve draw 6 amps???
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Old 07-15-2021, 12:32 PM   #8
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The refrigerator that's the topic here is Lepre 21's (the original poster) "residential" refrigerator with a motor driven compressor similar to what's in your kitchen at home either running directly on a 12v motor or a 120vAC motor driven off an inverter via the 12v batteries.

If it was an LP refrigerator it could run for several weeks on a single cylinder of propane.

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Old 07-15-2021, 12:56 PM   #9
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Chuck

Ah zo.

But the problem is still the draw. Unless our Dometic has a problem, I only got 1 1/2 days out of a single deep discharge battery.
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Old 07-15-2021, 01:21 PM   #10
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Your's seems in line. Outside air temperature, etc. affects this.

The data plate inside the refrigerator should show the power demand. Sure seems the motor is pulling an average of 6 amps.

These are horrible refrigerators for camping and really only suitable if plugged into shorepower all the time which is only "kinda camping" -- or several hundred pounds of batteries, a generator, and roof top full of solar panels.

They're dirt simple for manufacturers to install and are less expensive. I strongly recommend avoiding them.

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Old 07-15-2021, 02:26 PM   #11
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Thank you

Quote:
Originally Posted by Jimbo K. View Post
I plan to write up the results and post them in a new thread. I will add a link to it in this thread if you're interested.

Please do, nothing better than real world use as compared to manufacturing sales sheets.
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Old 07-15-2021, 06:07 PM   #12
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Disappointing

Thanks for all the replies. This is disappointing that we will not even be able to get through 24 hours of dry camping with 2 - 100 Amh batteries. We were not pleased when we picked up our brand new Motorhome and found it had a 1 way refrigerator. This is our 6th RV -on the first 5 we always ran the refrigerator on propane!
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Old 07-15-2021, 06:23 PM   #13
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Old 07-15-2021, 07:20 PM   #14
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What's the Reserve Capacity (RC) of these "100 amphour" batteries? If yours show cold cranking amps they're probably not true deep cycles.

The conservative rule of thumb that's worked for me since my days of multi-day/night racing offshore sailboats (where any use of a generator or the engine is a DSQ) is Reserve Capacity/2.4 = Useful amp hours. My pair of 6v Trojan T125s has a combined RC of 488 -- or just over 200 useful amp hours. Lots of weight -- I think they're 60# each. I wish there was an easy solution.

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Old 07-16-2021, 05:21 PM   #15
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Sorry, I cannot check the batteries right now. They were supplied by the factory, and were to be deep cycle. Unfortunately, another crisis struck when I was on the way to the dealer this morning - to get more things fixed on this disaster, towing my Jeep so I had a way back home when Iost power steering and brakes. Very scary. 2 1/2 hour wait for a tow truck. Anyone else out there lost power brkes and steering with only 2546 miles on the odometer?
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Old 07-16-2021, 08:57 PM   #16
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Quote:
Originally Posted by Jimbo K. View Post
As we speak I am running a test on my own GE 12V refrigerator and single stock Xpedition "100 Ah" battery. Based on experience and some previous preliminary testing, however, I seriously question whether I'll be able to get 50 usable Ah out of it -- hence the quotes.

I started the test at 9AM today with the RV in my driveway. Shore power had brought the battery to a full charge and the refrigerator to 34F. I disconnected shore power and began recording hourly battery voltage and state of charge readings as reported by a Victron SmartShunt. I also am recording hourly refrigerator temperatures. The SmartShunt also records historical cumulative power consumption.

I will stop the test when voltage reaches 12.0 and/or SOC reaches 50%, or bedtime tonight, whichever comes first.

I plan to write up the results and post them in a new thread. I will add a link to it in this thread if you're interested.
Here you go. Happy reading!
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Old 07-18-2021, 05:20 PM   #17
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Did you post your results from your test? I can’t see them.
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Old 07-18-2021, 05:27 PM   #18
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Originally Posted by Lepre 21 View Post
Did you post your results from your test? I canít see them.
Click the link in my previous post.
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Old 08-10-2021, 04:31 PM   #19
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Your link did not show in your post. Don't know what happened. Please re-post the link. Thanks.
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Old 08-10-2021, 05:50 PM   #20
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Your link did not show in your post. Don't know what happened. Please re-post the link. Thanks.
The word "here" is formatted as a link in post #16. You should be able to just click the word.
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