Inverter for dorm fridge online; looks good (so far) - Page 2 - Fiberglass RV


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Old 05-24-2012, 12:34 PM   #15
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Jack, I just speced out the electrical system for my Lil Snoozy with the goal being indefinite dorm fridge operation and a little lights, water pump, computer recharging, etc.

I am puttiing two Trojan T105 6v 220ah batteries on the tongue but pushed aft far enough so that the 124 lbs of lead only puts 80 lbs on the tongue. I ordered a 600w Samlex TSW inverter (fridge only draws 100 w but I want some extra power to cover starting loads) and a 30 amp Iota battery charger. Operating my Honda EU2000 genny for 4 hours a day will put 120 ah into the battery each day. If the fridge runs 50% of the time the genny is not running (I hope it runs less) that's 83 ah drain so I should be in the ball park.

I also ordered a Victron BMV600 battery monitor so I will be able to see the actual amp hours in and out and know when to run the generator.
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Old 06-22-2012, 05:23 PM   #16
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Update? Very curious about running that kind of appliance off batter/solar. If I can run my fridge off solar just during peak sunlight rather than LP it will help make LP last longer. I killed a small propane bottle pretty quick with the fridge running on gas.
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Old 06-22-2012, 07:14 PM   #17
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I'm running a cheap Black & Decker AC dorm fridge which draws approx. <1amp. Unfortunately, as electric heads better than mine will tell you, that translates to 8amps DC. My best swag is that with 2 group 27 batts and a sunny summer day and 80watts solar I might get around the clock once before reaching 50% DOD. My best run from battery at full charge at fridge startup and charged by solar during run is 16 hrs. Voltmeter said 12.3volts when I shut down. This with a single group 27. I really don't have 6-9C dollars for an efficient DC fridge. Good things about this one is it cost 69 bucks, it's a great fridge on shore power, and I have a convertible ice chest. Before I had a defunct 3-way and a convertible ice chest. Better to have something riding in the 3-way's spot that performs well at least on the grid. I am also told that creating DC by inverter is inefficient. Better to find a DC fridge probably.

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Old 06-22-2012, 10:24 PM   #18
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I am not building a solar system to run refrigeration, but I am curious how well it can work. I have the 3 way Dometic. I wonder how well it would work in 12V mode with 300ish watts of panel and 240ish amp hours of battery? May be useful when LP is not easy to come by.

Sort of a learning experience. I want to build a sustainable house someday, getting an idea, experientially, of what it takes to collect, store and use the energy needed for various tasks has a strong appeal.
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Old 06-23-2012, 07:03 AM   #19
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........ I wonder how well it would work in 12V mode with 300ish watts of panel and 240ish amp hours of battery? ...........
I believe the 3 way refrigerators draw about a steady 10 amps on 12 volts. So, that would be 240 amp hours a day. Did I read a guestimate of total output in amp hours per day to be equal to one full hour at maximum outout, or 25 amp hours in the case of 300 watt panels?
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Old 06-23-2012, 10:20 AM   #20
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Update? Very curious about running that kind of appliance off batter/solar. If I can run my fridge off solar just during peak sunlight rather than LP it will help make LP last longer. I killed a small propane bottle pretty quick with the fridge running on gas.
Dylan, I am not sure what you mean by a small bottle but I run my fridge for weeks on a 20 lb tank. If you are going through a 20 lb tank quickly, you may have a leak. Just a thought. Raz
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Old 06-23-2012, 11:55 AM   #21
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Nice job, a small suggestion would be to add a small round air vent on side to help keep the inverter cooler=more efficient.
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Old 06-23-2012, 12:16 PM   #22
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Heat has not been a problem with that inverter. It's located in a locker that connects to the area of the old fridge vents. Once the tasteful wood-grain divider or bulkhand was removed, it was in a position to benefit from the muffin fan which is located behind the upper vent. Actually, it hasn't even had a workout with the fridge; only get the internal fans on startup and just barely warm to the hands.

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Old 06-23-2012, 12:59 PM   #23
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Dylan, I am not sure what you mean by a small bottle but I run my fridge for weeks on a 20 lb tank. If you are going through a 20 lb tank quickly, you may have a leak. Just a thought. Raz
Interesting. Good data point.

It was a really small tank. 1 gal, 5lbs. I did use some for heat that day too, maybe it didn't get filled entirely. I use that little tank on the tongue on the move and put the big cylinder on the floor near the axle when underway. The thinking was to use it to keep the fridge going while moving, but I know how controversial that is. I just need to figure out how to get more current to the trailer from the TV, I don't seem to get much juice from the TV, perhaps I just need bigger wire.
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Old 06-23-2012, 01:07 PM   #24
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I believe the 3 way refrigerators draw about a steady 10 amps on 12 volts. So, that would be 240 amp hours a day.
Wow, that's not very effecient. I was just looking at this little fridge/freezer, 30 watts (2.5 amp), 60 amp hours a day.

http://dometic.com/enus/Americas/USA...ctdataid=90084

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Did I read a guestimate of total output in amp hours per day to be equal to one full hour at maximum outout, or 25 amp hours in the case of 300 watt panels?
I dunno, did you read that?

I hope to have up to 320 watts of panel, they are 12v panels, but apparently 17v is typical output, 320w/17v= 18 amps. So if 1 hour a day is a good rule of thumb, not sure how people with 50 or 80 watts of panel are reporting getting a good charge on a 80 amp/hour battery in a day.

Why didn't I ever take physics.
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Old 06-23-2012, 02:32 PM   #25
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Dylan,

I did major in Physics and it does help one every day of one's life.

Regardless I do have an 80 watt panel and it does the job not because it puts our tremendous amounts of power but rather because I use little power. I think that's a big part of successful solar installations.

I think minimizing usage is the key. I'm installing one on my son's trailer today and he needs to replace his power hungry incandescents with LEDs. His incandescent load with all lamps on represents 16 amp hours alone.

Our load with all LEDs on would be about 1.6 amp hours though we typically only have a couple on probaby less than 0.5 amp hours and generally only on at night for a few hours.

Our water pump draws a lot but really is only on a few minutes an hour.

Our TV draws about 1.5 amp hours and is only on early in the morning and at night.

My computer draws about 1.5 amp hours whan charging and runs for about 7-9 hours on a charge, it's a small netbook yet does the job well. Phones and e-books are barely worth mentioning.

We have made it easily on 80 watts....

I must admit we typically travel during periods of 'long hours' or are in sunny climates in the winter. I'm sure that helps. The 10 percent efficiency earlier mentioned in the thread I'm sure does not apply in Yuma, even without tilting panels. I'm sure the same can be said for any where in the southwest.

Now that we're in the NW where the Sun is extremely rare at this time of the year, it's at least bright for 15 hours a day. Though parked in our son's yard and plugged in does not require much DC. Howver we do not have our converter on and are using the panel to charge.

Our experience is that 80 can be enough. Certainly 320 should do the job.

Safe Travels and sunny days,
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Old 06-23-2012, 03:07 PM   #26
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"Regardless I do have an 80 watt panel and it does the job not because it puts our tremendous amounts of power but rather because I use little power. I think that's a big part of successful solar installations.

I think minimizing usage is the key."

BINGO
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Old 06-23-2012, 03:21 PM   #27
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"Regardless I do have an 80 watt panel and it does the job not because it puts our tremendous amounts of power but rather because I use little power. I think that's a big part of successful solar installations.

I think minimizing usage is the key."

BINGO
I hear that loud and clear.

But I'm still going to make and store all the power I can.
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Old 07-04-2012, 11:58 AM   #28
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I pulled up my old thread on dorm fridge for an interim report on "real world" use. May have minimal interest for the "dries" and minimalists and also for the "full hookup" crowd but anyway a report:

Friday, June 29 was a near record setting hot day in the northeast. We cooled down the dorm fridge on AC Thursday before heading for Nittany Mtn. KOA in Williamsport. PA. Inverter powered off a fully charged group 27 for the 4 1/2 hr. trip. Multiimeter said 12.3 volts on arrival in early afternoon. Set up in 97 degree temp. and I'd say the little fridge had its work cut out to make ice and was contributing to cabin temp. On a sunny site which would have allowed me to recharge on solar contribution. With the shore power, that wasn't a necessity. Muffin fan behind the upper vent helped exhaust compressor heat; would also help with inverter heat from locker comptmt. which is also open to the vent but I didn't detect much heat in the fins probably because getting some Venturi principle exhaust while moving. Saturday was perhaps ten degrees cooler and overcast; little fridge was freezing everything so I turned it down. Return trip Sunday fridge again inverter fed; multimeter read 12.45 volts on arrival Sunday afternoon. I'm satisfied that this level of performance has some utility for short weekend trips. The "They drive by night and seek refuge at Walmart" scenario might not be as satisfactory if not punctuated by some shore power (and water) sites. Unfortunately, may not be ideal recharge system as we think we're fringe season campers (if there is a fringe season in northeast). I'm taking the something is better than nothing view for now. I continue to be overly optimistic about the capacity of the greywater tank. Did not use shower but apparently we are pretty lavish about rinsing dinner dishes. Bought a 15 gallon wasterwater tote from Amazon Monday.

jack
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