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BC_Explorer's avatar
BC_Explorer
Explorer
Jun 16, 2015

Dorm Fridge for Trailer

I am thinking of adding a dorm style fridge to my small trailer. The fridge cubic feet size ranges from 3.1 to 3.3 depending on brand/model.

Most of these fridges pull 1.3 to 1.5 amps @ 110 volts. I currently have 2 x Group 27 batteries, a 1000 watt inverter and plan on ordering 2 x 100 watt solar panels to supplement my existing 60 watt portable solar panels.

A Champion 73534i 2000W Generator is in the fall budget plan to be used for winter camping. However and in the meantime, would the combination of the existing batteries, inverter and solar panels be sufficient to keep the fridge running for 3-4 day weekends? 90% of the time, the trailer will be in full sunlight throughout the summer. I have read through pages of this forum and could not readily find a good answer on this setup.

Thanks in advance.

8 Replies

  • MrWizard's avatar
    MrWizard
    Moderator
    Jun 19, 2015
    we are in and out of our fridge all day
    i would say our duty cycle is at least 40%
    we keep ice in the freezer and cold water bottles in the door
    we do open it a little less in cool weather
    if you calculate and plan for a 50% duty cycle, you leave your self some fudge room, where it comes to having enough energy
    AKA batteries and solar
  • BFL13's avatar
    BFL13
    Explorer II
    Jun 19, 2015
    I put a 3.2 Igloo (from London Drugs) in the truck camper and it all worked, but that was with a bigger battery bank. See my post here on that. (BTW a slightly bigger 3.3 had a better fridge layout for putting things, but wouldn't fit in the TC--was an inch too tall)

    http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/28391918/gotomsg/28391985.cfm#28391985

    You can do that but IMO you will need more battery or with just the two, then as well as the solar, be prepared to run the gen for an hour or two daily (running a converter that will do the 14.4v or so fast charge--if all it does is 13.6, you need something else.)

    Here is my initial testing results post

    http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/28286028.cfm
  • westend's avatar
    westend
    Explorer
    Jun 19, 2015
    jrnymn7 wrote:
    Westend,

    Would the OP's 1.4a rating (~170w) be the starting VA's, and not necessarily the operating VA's? And is it typical to see a 1 on : 4 off ratio, when sitting in a warm trailer?
    No, the LRD will be much higher than that, probably in the neighborhood of 6-8amps at 120V. I haven't found an accurate way to measure it. When the little fridge is moderately filled and ambient is 80f or less, I typically see a 1:4 duty cycle. Door openings will skew that as the box tries to regain the set temps.
  • BC_Explorer's avatar
    BC_Explorer
    Explorer
    Jun 19, 2015
    Thanks all for the input. I have ordered the 2x 100 watt solar panels and once they arrive, I will test the setup here at home and let it run for a few days to get an idea if more battery is required.
  • ktmrfs's avatar
    ktmrfs
    Explorer II
    Jun 16, 2015
    I've run a dorm fridge in a small home built toyhauler for over 10 years. My observations.
    1) rated current draw on 120V is the MAXIMUM under worst case conditions, typical draw is about 75% of the rated.
    2) figure a 30-50% duty cycle on the compressor, 50% only if it is REALLY warm inside the trailer, otherwise 30% max.
    3) 12V draw will be about 10% of ACTUAL current draw

    I can run the fridge, and other stuff in the trailer usually for at least two days on a pair of Trojan 6V GC batteries before I'm down to 50%SOC.

    When mine is running it typically draw 8A from 12V, so 8A*6Hrs/day= 48AH/day at 8Hrs/day it's 64AH/day. My trojans are 240AH, so over typical 2 days, I'm probably running a 25% duty cycle or less.
  • jrnymn7's avatar
    jrnymn7
    Explorer
    Jun 16, 2015
    Westend,

    Would the OP's 1.4a rating (~170w) be the starting VA's, and not necessarily the operating VA's? And is it typical to see a 1 on : 4 off ratio, when sitting in a warm trailer?
  • westend's avatar
    westend
    Explorer
    Jun 16, 2015
    I use a smaller fridge (dorm style) in my trailer. It is powered by 300AH battery banks (total) with a single 235W module, fed through a Xantrex Prowatt 1000 inverter. The fridge draws 80W when operating and the duty cycle is about 1:4. The LRA is much higher but that is instantaneous. Most refrigerators, even newer full size, are close to these specifications. A Kill-a-watt meter will measure exactly what the fridge uses for power.

    For clarity: I have no parasitic draw items in my trailer (alarms, circuit boards, etc.). I have 100% LED lighting.
  • jrnymn7's avatar
    jrnymn7
    Explorer
    Jun 16, 2015
    Whatever the draw is at 110v, you must multiply by 10X for the draw on the 12v battery bank. At a 1.4a/110v draw, for say 16hrs/day, that's 224Ah's per day, on a 12v system. Add to that another say 12Ah's/day for the inverter. A bank with a 20hr capacity rating of at least 472Ah would be needed, in order to maintain no less than a 50% soc, daily... and that would be very hard, long term, even on a set of true deep cycle batteries.

    A daily charge to true full, will be necessary, in this case, but that 60w panel would likely not even float an already full battery bank of that size, even on a good day.

    So no, the existing equipment would not get you thru a single day, let alone 3 or 4 days.

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