Charging & running Fridge on 12v frm TV

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  • irvingj
    irvingj Member Posts: 335
    Please see my post: http://tab-rv.vanillaforums.com/discussion/comment/35313/#Comment_35313
    concerning a 3-way fridge.

    Absolutely, using only 12 volts DC to run an electric heater is a very inefficient proposition because of the amp draw.  Ditto ST_Bob: only use the 12V setting on a 3-way fridge when plugged in to shore power, otherwise it'll suck batteries dry very quickly. (Please don't ask me how I know this -- and should have known better!)

    "Newer" 12V compressor types (electric only, either 12VDC or 120VAC, no propane option) are far more electrically efficient: either a standard reciprocating compressor with a 12V motor (with built-in step-down to 12VDC from 120VAC), or the Engel type that uses what's called a "swing compressor" (basically a solenoid and a spring), a very clever alternative and a very stingy user of electricity.

    Both are quite efficient, the Engel type being more so (talking about 1.5 amp draw here!). Either one is capable, because they use refrigerant gas compressors, of pulling down a warm fridge to normal fridge temps without the need for pre-cooling. They'll also be able to make ice in a freezer section, if so equipped.

    But they DO need electricity, hence the viable use of propane-powered units, i.e., 3-way or adsorption (is it really aBsorption now?) refrigerators.

    Extended boondocking? Propane might be the best way, even with its limitations. Solar recharging available with HD battery backup? I'd go with a 12V compressor-type unit.
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  • Nomad
    Nomad Member Posts: 7,209
    So you two seem to be saying that running on battery while traveling is a excercise in futility - Am I reading that correct?
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  • Photomom
    Photomom Member Posts: 2,217
    PXLated said:
    So you two seem to be saying that running on battery while traveling is a excercise in futility - Am I reading that correct?
    Isn't that what it's designed to do? Confused. 
    John and Henrietta, Late 2016 T@B S Max in Western New York
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  • Photomom
    Photomom Member Posts: 2,217
    So, isn't SOP to precool the fridge with 110V or ice before leaving home, then use 12V while driving? Does this not work?
    John and Henrietta, Late 2016 T@B S Max in Western New York
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  • jkjenn
    jkjenn Member Posts: 6,417
    Photomom said:
    So, isn't SOP to precool the fridge with 110V or ice before leaving home, then use 12V while driving? Does this not work?
    Yes. I cooled the fridge down for 2 days before I left last fall and put a couple of bottles of frozen water in when I packed. 5,000+ miles later, the one bottle that I left in the entire time was still frozen.

    2021 T@b 320 Boondock "Mattie Ross" | 2021 T@b Nights: 239 | Total nights in a T@b 455 | 2022 Jeep Grand Cherokee L Overland | T@b owner since 2014

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  • Nomad
    Nomad Member Posts: 7,209
    Mine's always cool being full-time so it's just switch-n-go :-)
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  • webcrawler
    webcrawler Member Posts: 133
    11 Amps would be no issue on the MKC.  It has a dedicated 30 amp circuit for the factory tow power.  
    Kennesaw, Georgia

    2016 Silver/Black T@B M@x S with Scuba Black interior.  2015 Lincoln MKC AWD 2.0L Ecoboost tow vehicle. Tekonsha Prodigy wireless Brake Controller.
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  • irvingj
    irvingj Member Posts: 335
    "So you two seem to be saying that running on battery while traveling is an exercise in futility - Am I reading that correct?"

    No, not in that case, providing, as has been mentioned: IF the fridge is already cooled down (and yes, previously-frozen water containers will certainly help here), traveling while using the (typical) meager 12V supply from the TV should be adequate to maintain temp-- just don't count on 12V alone, please, after you stop. At least, not for long. So, not necessarily futile over the road.

    Actually, on our T@B, I've used propane over the road with good results-- I know that's not recommended, but it just happened to work in my case with no ill effects, as far as I could tell.

    The RV "upgrade" we bought last year has an electric-only (2-way) fridge, and 300W of solar panels, and four HD batteries, so we've had no issues at all with running the fridge on "battery" 24/7 for weeks at a time. (It's actually more efficient at 12VDC than on 120VAC.) It can even make ice. --But that's not the case with a 3-way.
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  • Verna
    Verna Member Posts: 6,876
    irvingj said:
     It can even make ice. --But that's not the case with a 3-way.
    Oh yeah you can!  I made Coke Slushes, Ice Carrots, Frozen Lettice...a number of times last winter ;)
    Verna, Columbus, IN
    2021 T@B 320S  Boondock “The T@B”
    Towed by a white 2019 Ford F-150 4x4 Supercab, 3.5L V6 Ecoboost “The Truck”
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  • Nomad
    Nomad Member Posts: 7,209
    Verna - Yep. Not intentionally though :-)
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  • Verna
    Verna Member Posts: 6,876
    Correct, PXLated, especially the lettuce....yuck!
    Verna, Columbus, IN
    2021 T@B 320S  Boondock “The T@B”
    Towed by a white 2019 Ford F-150 4x4 Supercab, 3.5L V6 Ecoboost “The Truck”
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  • Cyclonic
    Cyclonic Member Posts: 1,232
    PXLated said:
    Mine's always cool being full-time so it's just switch-n-go :-)
    @photomom, Same as PXLated but for a different reason.  I keep it on shore power at home and just leave it on if I am going to be camping several weekends in a row (this will be weekend two of three coming up).  I just switch it to 12v during transit, if I stop I pull the plug from the TV to save its battery, since I am going to be on shore power when I reach wherever I am going.

    If it is going to sit a while, I precool it several days before leaving.

    As long as it is cooled, you should have no problems just switching to 12v and going.

    States the T@Bpole has camped, so far ;)
    Nathan & Becky... 2013 Ford F150 FX4 TAB HLR... 2012 LG T@B T@Bpole.
    Sterling, VA
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  • Ratkity
    Ratkity Member Posts: 3,770
    Verna said:
    irvingj said:
     It can even make ice. --But that's not the case with a 3-way.
    Oh yeah you can!  I made Coke Slushes, Ice Carrots, Frozen Lettice...a number of times last winter ;)
    Ewwww. Icicle carrots! Carrots are an evil veggie to begin with LOL.. apologies to those who like them. I shall relinquish my Lifetime carrot allotment to anyone who wants it!
    2017 820R Retro Toy Hauler from 2015 Tabitha T@B from 2009 Reverse LG Teardrop (but a T@Bluver at heart)
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  • Nomad
    Nomad Member Posts: 7,209
    And I'll throw in broccoli, cauliflower and kale.
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  • Photomom
    Photomom Member Posts: 2,217
    I love all those. Not purple beets. In grade school (back when they had cooks who would cook actual food) we would get beets once a week. The purple juice would run all over your plate and get in your mashed potatoes and everything, and you'd have to eat it or you couldn't get an ice cream cup. Traumatic. 
    John and Henrietta, Late 2016 T@B S Max in Western New York
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  • Photomom
    Photomom Member Posts: 2,217
    I just got one of these fridge monitors. Displays current temp along with hi and lo and has an alarm if temp gets too high or too low. Wireless so theoretically we can have it in the TV and monitor what the fridge is doing. Comes with two probes, that will give us a spare. 

    John and Henrietta, Late 2016 T@B S Max in Western New York
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  • Nomad
    Nomad Member Posts: 7,209
    Photomom - Where'd you get that?
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  • Photomom
    Photomom Member Posts: 2,217
    It came in today's shipment of RV stuff. http://www.amazon.com/AcuRite-Refrigerator-Freezer-Wireless-Thermometer/dp/B004QJVU78

    Thus far it seems acceptably accurate. The GE fridge holds well at 37/0 and the AcuRite is staying within 2 or 3 degrees either way now that it has settled down.
    John and Henrietta, Late 2016 T@B S Max in Western New York
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  • ChanW
    ChanW Member Posts: 3,165
    You really think it'll transmit into the TV? Seems like a lot of grounded 'shielding' to cut through.
    Chan  -  near Buffalo NY
    2014 S Maxx
    2011 Tacoma 4cyl ... edit: 2022 Tacoma 6cyl - oh yeah! 

     A_Little_T@b'll_Do_Ya
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  • Photomom
    Photomom Member Posts: 2,217
    ChanW said:
    You really think it'll transmit into the TV? Seems like a lot of grounded 'shielding' to cut through.
    As a test I put the monitor out in my car on the driveway, about 45 feet from the sensors inside the kitchen fridge. Still working. 

    Will report back when when we've had a chance to try this on a trip. Hopefully it will help us avoid frozen or spoiled food on longer trips. 
    John and Henrietta, Late 2016 T@B S Max in Western New York
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  • Sharon_is_SAM
    Sharon_is_SAM Member Posts: 10,061
    Photomom,  how is the Acu-Rite working?  I am thinking of getting one to monitor the temperature in the CS galley.  We already have a remote monitor for the ARB that works well.
    Sharon / 2017 T@B CSS / 2015 Toyota Sienna Minivan / Westlake, Ohio
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  • Photomom
    Photomom Member Posts: 2,217
    SAM said:
    Photomom,  how is the Acu-Rite working?  I am thinking of getting one to monitor the temperature in the CS galley.  We already have a remote monitor for the ARB that works well.
    Works fine. I keep one sender in the fridge and use the other either inside or outside the trailer depending on which I'm interested in monitoring. 
    John and Henrietta, Late 2016 T@B S Max in Western New York
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  • Sharon_is_SAM
    Sharon_is_SAM Member Posts: 10,061
    Thanks.  It's on sale at Amazon.
    Sharon / 2017 T@B CSS / 2015 Toyota Sienna Minivan / Westlake, Ohio
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