dorm frig / batt power ??? - Fiberglass RV


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Old 08-29-2014, 02:55 PM   #1
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dorm frig / batt power ???

Dorm frig powered by a battery
I am sure you can do it but the big questions is....can you it be done efficiently?
I am new to the world to electrical system in campers and have taken on the project of a complete remodel of a Amerigo. So I am green and have one questions that will surely lead to more LOL
I am planning in wiring my plug from truck to camper with a wire to charge the on board battery. Can this be done? I am also sure I will need a inverter and thinking the size I would need would be at least 2000 does that sound right? inturn will that allow me to run the dorm frig? how many battery's would I need for this 1 or 2 and what size? any help would be great!!!
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Old 08-29-2014, 03:49 PM   #2
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You have actually asked a number of questions. I'll try to address a few of them:

1. It's "Normal" to have a charging line running from your TV to your coach. It's best to include at least a circuit breaker in the line within the TV as well as a battery isolation so you won't have to unplug from your TV when parking connected overnight. In the case of the wiring, the heavier the better, a #8 usually does the trick, but you have to have an equally heavy ground wire as well.

2. If you ever want to run the refrigerator on 12 VDC you will need a inverter. Depending on how much the refrigerator and inverter draws in current, you may be able to run the refrigerator while driving. But that's a big Maybe...

3. Inverter size is dependent on your load, but you may not need a 2000 watt inverter. Check the draw of the refrigerator on it's info plate.

4. As far as batteries, it again depends on the load and how long you want to run off grid. You need to provide some numbers for the math wizards to give that advise. Suffice to say though, if you are going to be mostly off-grid for days at a time, it will take a couple of batteries to keep the refrigerator running all the time...

That's why LP refrigerators were invented for RV's. Because your Amerigo originally was set up for a 2 or 3 way refrigerator, you might want to rethink going electric. Yes, a dorm refrigerator saves a few $$ up front, but the LP one will run all of the time, no matter what planet you are on. Lots of used ones sell for well under $150

And that's my take.... there will be others
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Old 08-29-2014, 04:20 PM   #3
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There will be a wattage number on the name plate of the fridge. It had better be much smaller then 2000W, or your battery would be dead fast. It is likely less then 200W. This still represents a big load on your battery. Assuming your inverter is 100% efficient, (it's not) this would draw almost 17A from your battery. At 95, or so, amp hours capacity on your battery, your going to be dead in less then six hours. If you don't want to destroy your battery, then you should start recharging in three hours.

The draw is likely much less then 200W, but a 12VDC, (expensive) fridge will draw 3A, or less, and no inverter inefficiencies to worry about. This would be more then 15 hours of continuous operation, before you should start recharging.

It should be noted that fridges, depending on ambient temperature, probably run less then half the time, so double the time estimates.

Solar would help.
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Old 08-29-2014, 05:18 PM   #4
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Ok I got a good idea what your saying but, is that with one battery? I would buy a 12 v dc frige. If I was to use 2 battery's in a series would that near double my continuous run time? if 2 batterys are need what size should I be looking for? Thanks in advance
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Old 08-29-2014, 05:24 PM   #5
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If you get two 12 volt batteries you will have to wire them in parallel, otherwise you will get 24 volts
Two 6 volt batteries in series will give you 12 volts.
The amount of run time you get will be about the same, but the 6 volt batteries are more rugged and can be recharged many more times.
Inverters are very picky about input voltage and will just cut off when the input drops below a certain point.
SIZE? As big as you can afford/fit. Size = Capacity
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Old 08-29-2014, 08:13 PM   #6
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The terms of the query as initially stated keep changing; now 12vdc fridge has replaced the 120vac dorm fridge powered by inverter from batt. This is a slippery fish of a question!

Short answer to the question originally posed is NO, tried it! No. Not efficient use of juice, prohibitive number, weight and cost of batteries. The much more expensive dual voltage rv or marine fridge with Danby compressor is a much less demanding battery draw per hour of cooling and can be sustained by a battery bank and solar or genset recharging which will more or less be accommodated by the load capacity and footprint of a small trailer. Jack
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Old 09-02-2014, 12:17 PM   #7
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Two 6 volt golf cart batteries are the current gold standard for a 12VDC setup. Two 12 VDC batteries, (Group 24, or Group 27) with a selector switch also works.
Mini Master Battery Disconnect Switch | Princess Auto
12/24V Battery Master Switch | Princess Auto
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Old 09-02-2014, 12:25 PM   #8
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What's the switch for when using two 12 volt batteries, I just connect them in parallel and it seems to work out fine and you never have to worry about dragging one below 50%
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Old 09-02-2014, 03:47 PM   #9
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Well all in all it sounds like 2 6volt battery's are the way to go for a 12volt setup. I now feel pretty good on the battery side now to figure out what size inverter i will need and and how to wire up all my 12 volt lights. Then next is figure out the converter side from 110 volt to 12 volt and how to wire it all up. I got some reading to do LOL
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Old 09-02-2014, 03:55 PM   #10
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Make sure you understand what you need and don't need. For a 12VDC rv or marine fridge, you will not need to invert 12vdc to 120vac so you won't need an inverter.

Jack
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