ladywendolyn
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Post by ladywendolyn on May 28, 2017 11:26:06 GMT -8
In working on my trailer, it has been discovered that what we thought was the original 3 way fridge is actually only 110. It is built in to the trailer, but we can also see a propane line capped behind it, and there was a vent in the roof. So either the owners ordered a non propane fridge from the factory, or they carefully trimmed up this one to make it look factory. My goal is not to solve that mystery, but rather to make this fridge the most useful. For the record, no I do not want to switch it out. I'm keeping it for sure, as it is very unique and I have a back up one (same model) in case it breaks.
So the conversation my husband and I are having is, this.. "Is there a way that we could rig an inverter so that when on the highway, we could run the fridge off of battery power?" We are not concerned about overnights, as we usually have an electrical site. We do understand that we can buy a bag of ice. We would like to explore this option first, just to see if there are any possibilities. Here are a couple of questions for those with experience on this subject.. (I'm not asking for an electrical explanation or risky set-up that is out of the norm, so if thats your answer, please don't post it on the thread, as there are guidelines for electrical discussions on this forum, and the administrator has requested that questions be kept to basic issues.. thanks)
#1 Is it possible, to have your battery converting power to 110 while you are driving if you use the right kind of inverter?
#2. How would we establish the draw on the old fridge? It is the weird vintage electric kind with no moving parts motor ... it's super quiet and gets cold slowly and then stays cold. I assume there is a tool you can buy for measuring voltage draw when something runs? Does anyone know what it's called?
#3 Once we know the voltage draw, is there a specific inverter or battery thats most recommended for this application?
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Post by vikx on May 28, 2017 21:26:50 GMT -8
I haven't researched the answers to your 3 questions, but personally, I would freeze water jugs to keep the fridge cool on the road. When they melt, nice cool water to drink.
Old fridges usually have a huge start up draw, but yours sounds like a different egg. Can you give us the brand and model number?
Inverters are not a good idea if you're going to be boondocking. Even on the road, they can pull a battery way down. To operate a fridge with any kind of surety, a battery "bank" would be needed...
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ladywendolyn
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Post by ladywendolyn on May 29, 2017 10:12:41 GMT -8
Thanks. Yes our plan for boondocking would be ice or solar. I've decided to research this one step at a time and I'll post my findings on here so that anyone else trying to do this can have the info. I did read a thread by some modern trailer people yesterday talking about running a 110 fridge off 12 volt while driving etc. I learned a few things. -the original 12 volt fridges did work off the battery while driving. In fact some 110 fridges are 12volt reconverted to 110 (whatever that means), but basically they don't make the 12 volt /110 combo fridges anymore (or if they do they are not common), because people always forgot to switch them from 12 volt to 110 at campsites then their battery died overnight and they called the refrigerator place complaining but it wasn't the 12 volt system it was human forgetfulness. -I found out that the first thing I need to do it buy a power meter and run an test on my fridge to see how much power it draws. -once I know my power draw, then I can determine an appropriate inverter. -biggest issue is actually "can your alternator on your vehicle handle what you are doing?" -pre-1960's fridges are not necessarily power hogs (we will see)
So that's what I have learned so far. I will report back as I take steps to get a system in place. We bought a 100 watt solar panel today, but have no idea if that could pull enough power to boon dock with a fridge.
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nccamper
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Post by nccamper on May 29, 2017 11:38:40 GMT -8
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chametzoo
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Post by chametzoo on May 29, 2017 17:22:45 GMT -8
12 volt operation while driving is something of a pipe dream. I have a 3-way Norcold, but I run it on propane while traveling. The amperage draw is high enough in the 12 volt mode to make the trailer battery fall behind the charging from the tow vehicle battery. How is your tow vehicle wiring set up? Typically, installers use too small a gauge wire and then the losses are pretty large from the front of the vehicle to the back. Our fellow member “Cowcharge” should chime in here… most of what I know about trailer electrics is from him. If there is a way to PM him, he'll tell you the facts.
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ladywendolyn
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Post by ladywendolyn on May 29, 2017 18:32:43 GMT -8
Thanks chametzoo , I do believe one of the guys I talked to yesterday did say something about needing thicker gage wiring. I did talk to a few who do run their trailer fridge successfully while driving so thats what I hope to emulate. My trailer has all the skins off, and will get all new wiring, so I guess I will need to choose new wiring that will work for what we hope to do. One thing that has been suggested is to have more than one battery to hold more reserve power. We can probably do that as we have extra deep cell batteries from our boat and other trailer. Question will be whether all the drama is worth the effort. I have had ice boxes in the past and have done ice, on the road. It works ok, so I guess this will depend on a few things, such as how big the draw on the power is from the fridge. etc. I am not averse to trying it, if it's a possibility. Here are a couple of threads I came across from regular rv forums that have people running a fridge off 12 volt while towing. Of course opinions are all over the board for this.. but I'm trying to wade through them to see if there is a realistic option for us. A few weird opinions on here, and a few who claim to do this without issue. www.rvforum.net/SMF_forum/index.php?topic=28638.0www.irv2.com/forums/f84/using-an-inverter-to-power-the-fridge-88298.html
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turbodaddy
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Post by turbodaddy on May 29, 2017 19:22:26 GMT -8
Chamatzoo is correct, our's is a Norcold 3-WAY. We do not have it wired to charge from the 12 V system because it would deplete the battery(s)very quickly if not carefully monitored. We run the reefer on propane when towing or when boondocking without electrical hook-ups. We recharge the batteries with a 15 watt solar charger when no electric hookups are available. We do have wiring to charge the camper batteries while driving, but it is more like a trickle charge because of the distance from tow vehicle battery and camper battery. Please note, this is not the same as running the reefer on 12VDC. Do not plan on only running it on 12VDC.
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ladywendolyn
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Post by ladywendolyn on May 29, 2017 19:58:37 GMT -8
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Post by vikx on May 29, 2017 21:29:15 GMT -8
I had a very bad experience towing with the fridge on 12 volts. We were hauling horses North and drove overnight. Well... about 200 miles from our destination, the truck lights started blinking on and off in the middle of the night! Turned out the fridge was pulling more than the alternator could deliver because of all the running lights on the camper and trailer...
There are some interesting options out there today. I don't consider 12 volts on the road very reliable.
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turbodaddy
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Post by turbodaddy on May 30, 2017 3:37:57 GMT -8
Ladyw. We have a portable 500 watt power pack that we can use to run computers and stuff off of, but no built in inverter.
Propane for cooking,heat,refrigerator (and two lamps which we hardly ever use 'cause they throw off so much heat). 2 12v deepcyle 100 amp/hr batteries that can be charged at a plug in site with an automotive charger, or by a 15 watt solar panel while parked at a boonies site, or by the tow vehicle while traveling. All lighting is LED, we have a Fantastic fan, 2 small 12V fans and the furnace which is the big consumer of 12v power ( but it only runs for a few minutes at a time.) No pressure water, we use a hand pump and those 5 gallon jugs with a spout.
We use a marine battery selector switch and only run on one battery at a time...while (hopefully) charging the other by one of the above methods. Just have to monitor the batteries' condition every so often with a hydrometer. If they do get discharged to 50% we look for a campsite with power,and plug in the automotive charger. When parked at home we use a "battery tender" to keep 'em topped off. Been 3 years and it all works for us. I'm sorry if I am repeating myself from previous threads! Another nice thing with the propane refrigerator is that you can freeze juice containers to use as block ice in a cooler even when boondocking. Our camper came with the Norcold so it was included in the price. When it finally dies I'm not sure we'll want to fork out $700 to replace it, but I sure do like it! There is hardly anything better than being completely self contained for days on end in the middle of nowhere with almost all of the comforts of home.
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ladywendolyn
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Post by ladywendolyn on May 30, 2017 7:34:57 GMT -8
Thanks for the info turbodaddy. It helps to see the whole picture of what people are doing.
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cowcharge
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Post by cowcharge on May 30, 2017 7:52:28 GMT -8
Sure, you can run an electric fridge on an inverter while you drive. But it may take a bigger battery than you want to buy (or a bigger alternator than you have, if powered by the vehicle), depending upon how much juice the fridge draws. I ran a brand-new Energy Star 110v fridge off my inverter for three months straight last summer as a solar test, but it is a compressor type. It worked great, it only dropped my battery bank down to about 93% overnight, but I have a big battery bank and 410 watts of solar charging that easily keep up with its usage. My fridge only draws about 4-5 DC amps from the battery. Inverters themselves only use a fraction of an amp to run, they're quite efficient. But to make one amp of 120v AC the inverter will draw ten amps of DC from the battery or alternator. One advantage you have is that an absorption fridge doesn't have a high start-up current like a compressor model does, so you don't need an oversized inverter like I do. Also, an old absorption fridge doesn't have any sensitive electronics, so there's no need for a pure-sine-wave inverter, at least not for the fridge. The data you need is: The AMP draw of the fridge, not the voltage. An absorption fridge doesn't need that much heat, since ammonia boils very close to room temperature. So I wouldn't expect it to draw that much, but you need to find out for sure, because an old fridge could be very inefficient 50 years into its life, and I don't even have a guess for the heating element's draw. There may be a data plate on the back of the fridge that tells you how much juice it draws, but that was when it was new, and measuring is always better. Modern devices tend to use less than they say they will, so you may get a nice surprise from measuring it. Get a clamp-style multimeter to measure the amps, you just place the clamp around any available spot in the wiring without disconnecting anything. Some of them only measure AC amperage (all the attractively cheap ones of course), so make sure you know what you're buying if you ever want to also use it to measure amps on a DC 12v wire. Something like this, a very useful tool for 50 bucks for anyone concerned with electrical issues of almost any kind: www.ebay.com/itm/Greenlee-CM-1200-Clamp-Multimeter-AC-DC-1000A-True-RMS-with-Case-and-Test-Leads-/352067134897?hash=item51f8d625b1:g:3mcAAOSwlMFZJLKdEDIT: I didn't notice that was a used meter when I pasted the link. You can probably find a new one for about the same price on Ebay. Just make sure it also measures DC amps. If you measure the draw on the 120v fridge cord, you need to multiply the result by 10 to get the DC amp draw that an inverter will pull from the battery. And then multiply by the maximum hours you'll be driving (or boondocking) between battery charges in order to figure out the amp-hours your battery needs to hold to run it as long as you need. Also you don't want to go below 50% charge to make your batteries last for years, so you need to double your total usage of amp-hours when sizing the battery. If you use 100 amp-hours between charges, you need a 200 amp-hour battery. Since fridges don't run 24/7, to be the most accurate (and not buy a bigger battery than you need) you should also measure the duty cycle of your fridge. Duty cycle is how often and for how long it runs out of each hour, usually expressed as a percentage. A 50% duty cycle means it runs for 30 minutes out of every hour. In that case you'd take the amp-hours you calculated above and cut them in half. I assume the fridge will already be cold when you hit the road, and reasonably full of food. So measure the duty cycle that way too. You can substitute jugs of water for food if you don't want to put food in there just for a test, but you need to at least replicate the mass of food, because the fridge is much more efficient full than empty. Make sure everything has been in there overnight to get really cold, because it will run more often and for much longer to get cold than to stay cold. The hard part is having to unwaveringly stare at your meter for an hour in order to catch it every time it goes on and off so you can time it, without getting distracted waiting and having to start over. Hope this helps!
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nccamper
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Post by nccamper on May 30, 2017 8:56:40 GMT -8
A related point, when we tried leaving the fridge full as we drove it really bounced the items a lot. Glass is out. Things that can pop open are a mistake. Produce that can bruise suffers badly. Etc. We eventually decided to unpack the fridge into a coleman cooler when moving.
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ladywendolyn
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Post by ladywendolyn on May 30, 2017 13:01:42 GMT -8
cowcharge thanks for this info! I knew there was someone in the group who had been sorting out solar and batteries etc. but I couldn't remember exactly who. I will follow the steps you outlined. I don't mind creating a battery bank, and we have huge flexibility on the alternator as we own a car dealership and I can pretty much dictate the vehicle I want to use each summer. -Yes the fridge will be cold when we hit the road. I don't know if we would boondock with solar, although it's a possibility. But for the most part, the fridge will be cold on 110 when we pull out, and the goal is to keep things cold through the day till we arrive at an electrical site. I ordered a power meter from amazon yesterday, so once that comes, I will run a 24 hour cycle, then I assume I "listen" to the fridge during a few hours and see how often it goes on and off? I am also assuming that it would be a good idea to add extra insulation around the sides, bottom and top of the fridge cavity (not at the back where heat escapes), as this will help with the duty cycle? Thanks for the feedback..
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chametzoo
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Post by chametzoo on May 30, 2017 18:32:45 GMT -8
cowcharge thanks for this info! I knew there was someone in the group who had been sorting out solar and batteries etc. but I couldn't remember exactly who…. See… I told you Cowcharge is da man when it comes to this subject...
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