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Old 02-08-2020, 04:03 AM   #1
mazboy
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Your answer on Residential Refrigs

I was curious on how much power the residential refrig took. I came across this article.


https://www.gonewiththewynns.com/rv-...igerator-power


It didn't answer the questions I was interested in--- Questions: 'How many hours can you be on just 2-12 volt batteries before you need to hook up to power?'


Second question: 'Going down the road--lets say for 8 hours--how much power are you supplying through your truck?'
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Old 02-08-2020, 06:58 AM   #2
jeffba
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I have gone 13 hours down the road and the battery (yes, battery not batteries) read 12.5 volts. It was the standard Interstate battery that the dealer put in. never checked the AH rating


Now for your first question.
What AMP hour are your batteries are your batteries rated for??
How hot is it in the camper?
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Old 02-08-2020, 09:21 AM   #3
DutchmenSport
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Ours has the standard 2 batteries that came original with the 5er. We've went 10 hours hook up to the camper, then another 10 hours unhooked from the camper (we were in a motel that night), and then another 10 hours on the road to finish the trip home. Once home, the batteries still had enough power for the Lippert 6 point leveling to work, unhitch from the truck and auto level. I then plugged into shore power.

I think that's the longest we went unplugged from shore power.

We've done several trips over the last year when on the road, inverter running the refrigerator for 10-14 hours at a stretch. Never an issue with the battery being low.

I don't monitor volts and watts and micro seconds. That's just too intensive for me. I want to just enjoy the camper, not be a slave to it. So, knowing approximately how long I can run with something is good enough for me.

Anyway, that's my experience. Your's may be different.
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Old 02-08-2020, 09:22 AM   #4
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Mazboy,
I know it doesn't answer your question directly but Jeffba is onto something. There are several variables that will affect how well your residential fridge keeps things cold:


How hot is it in the trailer.
How full of cold stuff (particularly frozen water) is the unit.
Keep the door closed.
What rating are your batteries.


From an experience perspective, I can say we lost no temp at all on a two day trip with 8 hours parked (with no power source other than the batteries while parked) in 80F weather. When we got to our destination the batteries appeared to be fully charged. We had no issues at all with all 4 slides and the autolevel. I am reasonably confident that you could drive 8 hours a day and be parked the rest of the time indefinitely with no issues. But I don't know anyone that uses a camper that way.
If like us your only concerned for how the battery/truck charging maintains the temp in the fridge on the typical road trip, then I would feel safe in advising that you will not have any issues. I really don't think the better insulated and efficient residential fridges use that much power and the typical heavy truck alternator should have more than enough power to supply it.


If your looking at boondocking advice I will defer to someone else.


This is too funny. Dutchman must have posted his near identical while I was typing mine LOL. Great minds think alike I guess LOL
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Old 02-09-2020, 10:16 AM   #5
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ON question 1.... How long you can run on 2 12volt batteries entirely depends on the store capacity of those batteries (20 hour AH rating).

18cu ft Residential fridges uses about 140AH per day. You can do the math for the hours you need battery power. To avoid shortening your battery life (non Lithium) you'll need about double that number of AmpHours. For example if you use the 8 hr number you mention, your fridge will use about 50AH. So you should have about 100AH of battery capacity (use the 20hour AH rating supplied by the battery mfr.) to avoid harming the battery life. We are only discussing the fridge mind you and only for the time you will be towing. Less than that battery size amounts to battery early death. How you use your rig really determine what else you need battery power for.

On question 2...Unless your truck and rig are specifically wired up to charge your rig batteries from the truck while towing... then none.
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Old 02-09-2020, 10:36 AM   #6
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Quote:
Originally Posted by BiggarView View Post
ON question 1.... How long you can run on 2 12volt batteries entirely depends on the store capacity of those batteries (20 hour AH rating).

18cu ft Residential fridges uses about 140AH per day. You can do the math for the hours you need battery power. To avoid shortening your battery life (non Lithium) you'll need about double that number of AmpHours. For example if you use the 8 hr number you mention, your fridge will use about 50AH. So you should have about 100AH of battery capacity (use the 20hour AH rating supplied by the battery mfr.) to avoid harming the battery life. We are only discussing the fridge mind you and only for the time you will be towing. Less than that battery size amounts to battery early death. How you use your rig really determine what else you need battery power for.

On question 2...Unless your truck and rig are specifically wired up to charge your rig batteries from the truck while towing... then none.
Without all the scientific numbers and such, how long would you say the AVERAGE large deep cycle battery would power the fridge? Yeah I know they make them in all different sizes, maybe a range?

I thought the rigs were wired up to charge from the truck from the factory? There is a charge pin on the 7 pin connector on all trucks setup with a factory harness isn't there? I know mine has it on the truck side for sure. I seem to recall seeing a wire headed to the batteries from the harness?
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Old 02-09-2020, 11:06 AM   #7
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What's an average deep cycle 12v battery?

50 AH battery could run just a residential fridge for about 4 hours (6 hours for a 75AH battery and 8 hours for a 100AH battery) before you are going below 50% of its capacity which is where lead acid or agm are vulnerable to early death when repeatedly drained below that level. Lithium are not so affected by this but that is a different discussion. If you go from campground to campground with electric hook ups, with a residential fridge, it uses about 6 amps per hour while on battery power. Using reg deep cycle batteries (non lithium) you need to double that to get decent battery life. Draining a reg deep cycle battery down to nothing repeatedly will murder it fairly quickly.
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Old 02-09-2020, 11:11 AM   #8
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On the truck charging, that plug does not provide the power to recharge batteries. If wired properly it will provide a "maintenance" charge but it won't provide enough power to recharge a battery. The set up in the truck is not designed to provide a full on recharge.
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Old 02-09-2020, 01:29 PM   #9
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While at an RV show a few years ago, the dealer had this posted in a Fuzion trailer.
Attached Images
File Type: jpg IMG_20170127_1602388.jpg (213.7 KB, 40 views)
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Old 02-09-2020, 02:11 PM   #10
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17 hours till battery depleted. not good for the battery... fine for the fridge. if you took it down to only 50% you'd have about 8 hours useable battery capacity. I'm guessing the two group 27 batteries recommended in the link provided by Mr Pachu are therefore around 100 AH total at 12 volts give or take. 8 hours is a long haul for one day of travel. If you pull in and plug in overnight, your battery will be fine the next morning... ready for another 8 hour run, if that is the way you roll.
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Old 02-16-2020, 05:01 PM   #11
H. John Kohl
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Residential Refrigerator 12 volt battery usage with inverter.
I took the 2017 3721 to a service shop. We parked in their driveway over night. Here are the Power/amp hour readings and calculations I have. When we arrived at 3pm here is the info:

Date. Time. AH Reading
1/6/20 3:12 PM -1.5

We used 167.5 amp hours in six hours powering the refrigerator, lights, furnace, TV with Sat receiver. Which showed 27.37 amp hours per hour with those power draws. No microwave or other night power draw. Water heater was on propane.
1/6/20 9:19 PM -169 -167.5 -27.37

From 9PM bedtime to 6:30 am we used 193 amp hours at 21.05 amp hours per hour.
1/7/20 6:29 AM -362 -193 -21.05

We moved out and the rest of the information was only powering the refrigerator.
1/7/20 8:21 AM -402 -40 -21.33

I did not take a reading at 10 am when we left the service shop however my solar 1300 watts did not get much sun so it ran the inverter powering the refrigerator and put 26.8 amp hours back into the batteries averaging 4.21 amp hours per hour.
1/7/20 2:43 PM -375.2 +26.8 +4.21

I hope this helps people understand the battery impact the residential refrigerator has. I can add more details on equipment if desired. Note the 3 - 9 pm time was using the Magnum 3012 inverter. The rest of the time was using the Magnum 1000 which ONLY powers the refrigerator.
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Old 02-16-2020, 05:29 PM   #12
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Quote:
Originally Posted by BiggarView View Post
On the truck charging, that plug does not provide the power to recharge batteries. If wired properly it will provide a "maintenance" charge but it won't provide enough power to recharge a battery. The set up in the truck is not designed to provide a full on recharge.
So your telling me the heavy duty alternator used on the average diesel truck does not put out enough juice to recharge the starter battery on the truck either?
So an alternator on the truck won't run the fridge without using any battery power? I find that very hard to believe but I am no expert.
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Old 02-17-2020, 10:06 AM   #13
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Extra measure

I carry an extra deep cycle battery in a separate case. It is my GP battery for anything and everything. Our ref draws 12A with the compressor running and about 2-3 at rest. Love the res ref.
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Old 02-19-2020, 05:10 PM   #14
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I say the OPs link is not correct in several ways.


I ran a test not long after getting our new 3791 home. On a 60 degree ambient temperature day running on only the 2 12 volt batteries (no shore power), our residential reefer ran over 32 hours b4 the battery voltage dropped to 10.5 and the inverter kicked off. This test is extremely hard on the batteries.


Replying to what retchief said.... while running on the inverter, the wattage ran from ~50-120 - that's watts not amps as displayed on the inverter. I never caught the reefer in defrost cycle which I'm guessing would be ~300-400 watts for a few minutes every 8-30 hours. I've worked on these reefers for years so that's a good "guess".



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