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Old 08-05-2017, 07:17 PM   #1
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Default Fridge-How long on house batteries

We are driving our 2017 Travato 59k to the Finger Lakes in Oct. We will be staying one night in a hotel. Since we won't be plugged into shore power overnight, will our small fridge operate on house batteries? (It operates on both but not propane.) We will be driving all over so the batteries should be fully charged; however, we will be attending a playhouse for a couple hours mid afternoon. I just don't know what to expect with the fridge.Oh, and we do have a solar panel on the roof, but I understand that is trickle power. Please advise! Thanks in advance.
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Old 08-05-2017, 07:24 PM   #2
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I don't think you'll have any issues. On the display panel, you can see your voltage - 12.7 or above is 100% full. When it gets down to 12.1 volts, you are about 50% and should seek recharging. Your refer should be fine for 2 or 3 days with nothing else on. If you are constantly running the overhead fan, then a little less.

With two batteries, you have 110 amp hours until you get down to that 50% mark. Your refrigerator uses on average 3 amp hours when it's running. How much it runs depends on how hot it is outside and in your van of course. Your overhead fan uses 1-2 amps when it's running. Other assorted items like lights, tv, radio, water pump, co detector, etc, can use 2-3 amps depending on what you are running. All that said, do the math and you'll see how long you can go.
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Old 08-05-2017, 07:37 PM   #3
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Shouldn't need a hotel room, unless you need air conditioning .
That's what these units are for.
I never go to camp grounds for shore power.
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Old 08-05-2017, 07:50 PM   #4
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FWIW, your solar panel is 100 watts. That's more than trickle power. On a sunny day, you should get 5 amps out of it.
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Old 08-05-2017, 07:54 PM   #5
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Thank you for your reply. FYI--we are staying in a hotel since we originally planned to attend an evening performance, and we just didn't want to drive a distance t o a campground and then try to hook up late in the evening. We are in our 70's and taking the easy road. We have never dry camped and dont plan to. Our preference.
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Old 08-05-2017, 08:27 PM   #6
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Old 08-05-2017, 08:49 PM   #7
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This video is wonderful! Looks just like the inside of our coach! Thank you SO much for sending it!
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Old 08-06-2017, 11:27 AM   #8
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This video is wonderful! Looks just like the inside of our coach! Thank you SO much for sending it!

You are welcome.

I hope this video gave you more confidence to go further and longer.

Enjoy !
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Old 08-06-2017, 02:31 PM   #9
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My understanding is,

An empty refrigerator cycles on and off more often than a refrigerator full of food.
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Old 08-06-2017, 05:53 PM   #10
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Quote:
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My understanding is,

An empty refrigerator cycles on and off more often than a refrigerator full of food.
+1

Agreed.
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Old 08-06-2017, 06:44 PM   #11
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+1

Agreed.

I don't know much about this subject, but I agree. But if the question was which uses less amps WITH the door staying shut for 10 days to make the point, seem like the empty one would win, fewer amps needed.

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Old 08-06-2017, 10:00 PM   #12
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Actually, a full refrigerator should take less energy to keep cool than an empty one. Less air volume to cool. Of course keeping the door shut helps immensely.
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Old 08-07-2017, 02:47 AM   #13
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Quote:
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I don't know much about this subject, but I agree. But if the question was which uses less amps WITH the door staying shut for 10 days to make the point, seem like the empty one would win, fewer amps needed.

Bud
If the fridge has air only,
every time you open the door,
the cold air escapes easily.

If you have a block of ice inside,
when you open the door,
only the surface area of the block is affected.
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Old 08-07-2017, 02:57 AM   #14
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The whole "lost air when you open the door" thing is mostly myth. Yes, you lose some "cold", but the specific heat of air is so low compared to the contents of the fridge (and of the fridge itself), that it can't possibly make a material difference, unless you leave the door open for a very long time or have a leaky seal (in which case you will get continuous convective losses).

As for whether a full or empty fridge will consume more energy, "full" will win, but mostly because the larger thermal mass will cause the compressor to run less often, so you save the start-up current. Other than that, it doesn't matter much.
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Old 08-07-2017, 03:23 AM   #15
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Agree on the thermal capacity of air, it is tiny in the big picture. I saw a study where they attributed a large part of the heat loss in a frig that gets the door opened, like all do, to the condensing out of the water in the air that replaces the air that flows out when you open the door. It is also a continuous flow and condensing on the cold surfaces as long as the door is open as it is self generating due to gravity. Once close, all the condensing is only on the air in the frig, unless the gasket leaks.

They also claimed that an empty frig uses more power because of convection from the hotter are up to the cooling coils, which happens more in the empty frig. The air getting stirred makes it transfer heat from the walls and door faster..

Kind of all makes sense, though.
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Old 08-07-2017, 06:14 AM   #16
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Quote:
Originally Posted by PinIN View Post
My understanding is,

An empty refrigerator cycles on and off more often than a refrigerator full of food.
Over, say, a 24 hour period, does an empty refrigerator consume more amp hours than a full one?
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Old 08-07-2017, 01:25 PM   #17
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Quote:
Originally Posted by PinIN View Post
My understanding is,

An empty refrigerator cycles on and off more often than a refrigerator full of food.
Also, prevailing outdoor temperature has a substantial impact on energy consumption. That video appeared to have been made in northern Iowa; it's typically warmer in most other places in the country.
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Old 08-07-2017, 02:09 PM   #18
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The video doesn't state the type and capacity of the Travato, but research indicates it has two 100a AGM batteries. They also allow their batteries to drop to 25%, which I understand shortens the life of the batteries.

I, too have a 100W solar panel and two batteries, but my compressor refrigerator is twice the size and my batteries are flooded wet cell.

Based on my test (with an empty fridge), I have about 10 hours on battery power if I run the refrigerator, ceiling fan and a couple of LED lights (assuming I don't want to drop below 50%). Yes, the solar panels can keep up during the day, but they can't re-charge the batteries while the fridge is running - they don't make enough power.

This means that I have to start the engine or generator each morning before the panels get enough sun to help. Works out fine because I use that opportunity to run the coffeemaker and blow dryer. Once the batteries are charged in the morning, I'm good for another 24 hours.

I'm mentioning this because I want to encourage the OP to perform their own tests before taking a video at face value.
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Old 08-07-2017, 02:23 PM   #19
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Quote:
Originally Posted by cruising7388 View Post
Over, say, a 24 hour period, does an empty refrigerator consume more amp hours than a full one?
The fridge will cycle more often, as stated, but each cycle is shorter. Theoretically, it would net out to a wash, except for secondary effects such as the fact that each start of the compressor takes some extra energy.

The "internal convection" effect that Booster mentions also probably has validity. How much, I do not know--no doubt it depends on how well-insulated the fridge is. This effect (but not the frequent-cycles) could be largely eliminated if you were to fill your fridge with bubble-wrap.

There are no doubt many other minor effects going on. As they say, "the difference between theory and practice is greater in practice than in theory".
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Old 08-07-2017, 02:39 PM   #20
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Quote:
Originally Posted by Phoebe3 View Post
Based on my test (with an empty fridge), I have about 10 hours on battery power if I run the refrigerator, ceiling fan and a couple of LED lights (assuming I don't want to drop below 50%). Yes, the solar panels can keep up during the day, but they can't re-charge the batteries while the fridge is running - they don't make enough power.
Were your 10 hours from full to 50% in the dark (overnight) or did they include time when solar contributed?

I might be able to do this test overnight, if I checked the voltage before the sun comes up (when solar charging changes the voltage).

Thanks for the good information.
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