Advice to prospects and buyers of campers with compressor refrigerators

RC Pilot Jim

RC Pilot Jim

Senior Member
Joined
Nov 19, 2010
Messages
1,546
Location
San Diego Calif
[SIZE=10pt]Disclaimer: This article is aimed at prospective or new buyers of the regular Four Wheel Campers or campers that come with compressor 2-way refrigerators. I am not a technician or engineer. Following information is based on 2 years of research and personal experience.[/SIZE]

[SIZE=13.3333330154419px]Overview[/SIZE]
[SIZE=12pt]There still seems to be a lot of confusion for the average compressor refrigerator owner as to whether they need one battery or two, roof solar panels or portables.[/SIZE]

[SIZE=12pt]My advice[/SIZE][SIZE=12pt] if you purchase the camper with the Dometic compressor refrigerator:[/SIZE] [SIZE=12pt]buy the Aux battery system with TWO batteries…And TWO solar panels - two 100 watt solar panels on the roof or one panel on roof and one 60-100 watt portable - Regular heavy (24 pound panels) or the lightweight ( 4 pound) bendable 100 watt panels from Renology or Global Solar.[/SIZE]

[SIZE=12pt]Third party panels: [/SIZE]
[SIZE=12pt]Solarblvd.com has good prices on regular (heavy) panels . [/SIZE]
[SIZE=12pt]Lightweight bendable panels[/SIZE]
[SIZE=10.5pt]Renology [/SIZE][SIZE=10.5pt]http://www.renogy-st...tHXAaAkmS8P8HAQ[/SIZE]

[SIZE=10.5pt]Global Solar [/SIZE][SIZE=10.5pt]http://www.globalsol...ible-modules/rv[/SIZE]

[SIZE=12pt]Reason why…..[/SIZE]
[SIZE=14pt]Dometic compressors refrigerators[/SIZE][SIZE=12pt] – [/SIZE]

[SIZE=12pt]Dometic/Waeco website specs list amp draw for the 65 liter at 3.5 amps.[/SIZE]

[SIZE=12pt]Brenda at Four Wheel Campers quotes 4.8 amps average.[/SIZE]

[SIZE=12pt]I know manufacture specs were produced in a lab environment under ideal conditions. Field conditions are [/SIZE]different[SIZE=12pt]. For this article I am rounding off to an average of 5 amps (model 65L) per hour depending on ambient temperature and number of times door is opened .[/SIZE]

[SIZE=12pt]At a 5 amp draw one battery will run the fridge maximum of 8 hours. Adding the furnace blower, fan, lights (couple hours at night) pushes average up to 6 - 7 amps per hour which DECREASES ONE battery running time to 5 - 7 hours per night. Average Night time darkness 11.5 -14 hours.[/SIZE]

[SIZE=13.5pt]Solar panel output:[/SIZE]
[SIZE=12pt]A 100 watt panel outputs 5.8 amps max in June -August ( sun high in sky- 11am-2pm). In October - March output drops to around 60% - about 3.5 amps (sun low in the sky) because roof panels can't be tilted towards the sun. [/SIZE]

One solar panel in winter will output approx 3-4 amps an hour NOT enough to run the Dometic and charge the battery.

[SIZE=14pt]Reason to add one roof solar panel at time of order[/SIZE][SIZE=12pt]:[/SIZE]

[SIZE=12pt]When Dometic is running and engine is off while out sightseeing, battery is being drained. Restarting and driving for less than 4 hours doesn't top off the battery. Owner will need to add one 100 watt panel on the roof to just run the fridge during the day (two panels to also charge the battery).[/SIZE]




[SIZE=14pt]For new owners unfamiliar with the process[/SIZE]

[SIZE=14pt]Dometic 65L compressor refrigerators[/SIZE] –
draw about 5 amps per hour. One 80 amp hour battery with 40 usable amp hours will run the fridge ONLY for 8 hours (40 divided by 5 = 8 hours) Reason: 12 volt devices stop working when voltage drops below 12 volts - about 50% of the battery volume.

You will experience at least 11 hours of night darkness (unless you’re in Seattle or Alaska) so one battery is NOT enough capacity to last the night.

One battery example:
Sun sets at 7:30 pm… Fridge cycling on and off…At 3:30 am (8 hours later) fridge shuts off because the voltage is less than 12 volts. Sun rises at 7 am. 4.5 hours passes until sunrise solar begins charging battery back to 12 + volts. After 2-4 more hours with all electrical devices off voltage has risen enough to turn fridge back on.. Fridge has been off 6 or more hours before cool down starts. How warm is the inside of fridge at start of cycle? What is the condition of your food?

And you won’t be drawing just 5 amps an hour because of the other devices you use. I figure average draw 6-7 amps per hour.

[SIZE=12pt]Except for the Dometic compressor fridge and heater and maybe the Fantastic Fan (in summer), the rest of the devices will run for a portion of an hour a portion of the day. For instance unless you’re using the shower your only running the water pump maybe 5 minutes per day so the water pump draws about half amp all day. Where with the heater you might be running it 4-6 hours per day for an average of 1 amp per hour (24 hour day). [/SIZE]

[SIZE=14pt]Two Solar panel justification[/SIZE]

[SIZE=12pt]I never thought I needed a roof solar panel because we try to park in the shade when camped...and then it is not as efficient. However when we are traveling with the refrigerator running and stop to sight-see the roof solar panel continues to run the fridge and charge the battery, so when we do stop to camp in the shade the batteries are full. Buy two panels.[/SIZE]

[SIZE=14pt]Battery monitor[/SIZE][SIZE=12pt] with digital read-out tells owner percentage of full, and amp draw to determine if solar input is keeping up with device draw.[/SIZE]

[SIZE=12pt]Since adding the Trimetric battery monitor AND the solar panel on the roof, we now know the condition of the battery all the time.[/SIZE]

[SIZE=14pt]Sure Power[/SIZE]
[SIZE=12pt]A component of the Auxiliary Battery system[/SIZE]

[SIZE=12pt]How it works?[/SIZE]

[SIZE=12pt]If the voltage draw from the camper drops below 12 volts….The "Sure Power" auto-disconnects the camper battery from the truck alternator to prevent the truck battery from being discharged by the camper devices (fridge). To electrically reconnect camper battery to truck alternator you need to plug into "shore power" or "solar power". Once voltage is above about 12.1 volts truck alternator starts charging batteries again.[/SIZE]

[SIZE=12pt]By the way the only method to determine if the “Sure Power” disconnects the camper batteries from the truck alternator is a digital battery monitor that shows voltage, amp draw or amp charging, and a percentage of full. [/SIZE][SIZE=12pt] New owner should[/SIZE][SIZE=12pt] at least add a digital voltage meter [/SIZE][SIZE=12pt]if the new camper didn't come with one as part of the solar controller.[/SIZE]

[SIZE=12pt]If read out is below 12 volts you are probably disconnected. To verify - start truck engine. If voltage doesn't increase to at lest 12.9 after about 60 seconds you are disconnected. If a campsite with hookups is not available and you have no solar panel your food will probably spoil before you can find a 110 volt electrical source to turn the fridge back on and start charging the battery.[/SIZE]

[SIZE=12pt]Hope this information helps. If I left something out please tell me and I will correct it. Questions please ask.[/SIZE]
 
Right on RC-it took me almost 10 years of trial and error, different suspensions, air bags, different types of solar panels, and all the rest, to get my Granby set up with 2 Renoly 100w solar panals, two atm batterys, a 110 compressor frig/freezer and 30amp comptroller! They didn't have that set up when I bought my FWC in '05, so if I ever buy a new one, it will have that type of set-up. Yep, happy and content now, gee, wonder what I add next :giggle: ?

Smoke
 
Amen Smoke. With my Engle top loader I only need one Renology on the roof and one camper battery. Now the system works great for us. :)
 
On my system there is an audible 'click' when the separator kicks in and out when the batteries are low and the engine is running. Seems to take 6 hours or more driving at highway speeds to get past that stage and let the alternator charge full time. I found that out on a trip to the Everglades where the temp and humidity were both in the 80's 24/7.
 
Thanks Jim for your help and advice. I emailed Brenda and FWC is using a Zamp ZS-15AW controller and the cost is $105.00. Unfortunately, its too late for me to add the solar charger since I’ll have pay another 200$ change order fee. Base on my research, the controller install is pretty straight forward so I’ll install it myself. The only question I have cable management on the roof.

I like how JATAC installed their panel using right angle SAE connectors:

http://www.exploringoverland.com/overland-tech-travel/2012/12/12/power-for-the-jatac.html
 
Glad it helped. You can always purchase a controller later when you wire up your system. When you do try to buy a system with a controller that has a built in battery monitor that gives you a digital read-out of voltage, amps in and out, and percentage of full value.

Lastly, wonder where he found the right-angle "SAE" 12-2 connectors (see picture):
8267745384_081c04a1f3.jpg


We have been trying to buy them for months.
 
One thing that I think about when it comes to solar panels is, they can extend the life of your batteries because they reduce the depth of discharge. So, even if you don't have a system that uses lots of power, solar might still be worth considering. Maybe just a smaller system.

Steve
 
Lastly, wonder where he found the right-angle "SAE" 12-2 connectors (see picture):
Click to expand...
Tom Hanagan has been trying to find another source for those ever since, in lots of fewer than 10,000.

NorCal Steve is spot on with his advice about discharge. We've lived exclusively on solar and wind power for 13 years now, and have learned the hard way that battery life is directly proportional to how well you keep them charged. If your system is not reaching 13.5 volts every day or close to it, you are compromising the life of your batteries.
 
I have made three upgrades and not installed solar, yet (80 litre Dometic) -

1.) LiFePo4 battery ($900), which has lots of amps and does not mind discharging.
2.) Upgraded FWC wiring to camper (truck side of Attwood plug) to 2 gauge - most more amps to battery - regularly charge ar 23 amps at idle.
3.) Upgraded the solenoid to one that I can manually override and program for automatic use (lets me get charing quicker).

Altogether Solar would have been a lot cheaper. I will still probably add solar someday, but for now it works. The LiFePo4 battery will hopefully last the life of the camper - the manufacturer claims 2000+ full discharge cycles but I never discharge below 30%. Time will tell.

Since I plan to spend a lot of time at the beach (fog) and in the redwoods Solar would not give me much, but I agree it would help charge when driving. Plus I plan to use my roof. When I put in solar I will probably put 15-30 watts for the truck batteries and 50 watts for the camper.
 
We have 2 batteries, 100w solar, and the 80 litre fridge. When we were in the Smoky Mountains we had a lot of rain and camping in the shade. We did drive to different hiking trails. With the fridge and CPAP machine we never had an issue with battery levels. We were very careful about use of lights, relying on our battery operated ones. We also made limited use of the furnace, using it to warm things up in the morning. I should probably knock on wood. jd
 
Two batteries, 100w solar on roof and 65 liter fridge. Have not had to hook up the solar in a bag on my Big trip to the east coast. One week parked in Baltimore and 100w kept the batteries full 13+ volts end of each day. It was cold and snowing there. In Key west set two days and low voltage was 12.44v. If you drive every other day 100w looks to be enough. I do have 6 gage wire running from the truck to the camper.


Doing laundry in St Joe Fl. Headed home.

Bill
 
Bill, what gauge running from roof panel to batteries?

While in Baltimore, low temperature helped the fridge cycling, however you probably ran the furnace 24 hours per day, right?
 
Jim, very good analysis and very accurate based on my usage data as well. As you said, many factors play into the scenario and what will actually work but generally, your recitation of what is needed is spot on.
 
Jim,

Thanks for posting this super helpful information.
It's amazing how much you learn after getting your system to work just right.

My advice is to make sure you have enough solar to both charge and run your battery/electrical system.
If your compressor fridge is going to take 4-6 amps per hour of power, 100 watts of solar is only going to run that fridge when the sun is at optimal position and you are not in the shade.
You need enough power coming in (solar, truck, generator or wall charging) to run your system and charge your batteries.
Otherwise, you run out of power.

100 watts of solar is about 4-6 amps per hour in ideal conditions.
200 watts of solar is about 8-12 amps per hour in ideal conditions.

So with 200 watts of solar and a compressor fridge running at 4-6 amps an hour, you still have enough solar (still 4-6 amps) to charge your batteries while the fridge is running.

You can always charge from the truck or a generator too, but once your system works - it is pretty amazing.
 
I suppose if I'm desperate I could always toss a couple of chunks of dry ice in the fridge and turn it off.
 
Since you are offering this for prospective buyers, what is the cost of all components if self installed? What would you estimate the cost if professionally installed to support a compressor system? Just curious?
 
Jim, I'm confused - are you saying your Dometic averages 4.5-5 amps per hour x 24 hrs for a total draw of 108 - 120 amps per 24 hrs?
Thanks,
Tim
 
Reviewing this reply I made some errors in math which I corrected this morning.

Kispiox,

Assuming you ordered your camper with the auxiliary battery system and two batteries, and two solar plugs are now standard on the new models, you just need to buy the solar panels, solar controller, and a 10 amp fuse. as the camper is wired for solar.

The Lightweight Renolgy panells are $200 each. MorningStar SunSaver 20 L - $87.00 (solarblvd.com). Misc glue, fuses about $25.00 = little over $500.

Aluminum framed panels are about $ 135 each (solarblvd.com) and weigh about 25-30 pounds each

I installed the panel on the roof, the controller myself. Guessing a Pro installation labor $75 - $150.

CaptM
Lets round the draw to 5 amps/ hour or 120 amps in 24 hours. One 100 watt panel would replace about 139 amps in July and 96 amps Oct - April. as long as your not running any other 12 volt devices within a 24 hour period...Obviously You are only concerned with the hours of darkness as the panel or panels run all your devices (mostly the fridge during the day)
 
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