Danfoss type refrigerator questions....

[billtrev]

Danfoss type refrigerator questions....

We are thinking of replacing our still working ten year old Dometic 2662 with a Vitrifrigo dp2600iAc.

Our trailer has 400 watts of solar and two group 24 batteries on the tongue which I plan on replacing with two golf cart batteries in the very near future. Our battery capacity will be about 220 AH.

Also have a Honda 2000i which we would rather not have to being with us.

We boondock / dry camp often.

My concern is that our battery bank is too small to support the 12v refrigerator in less than ideal solar conditions.

First question - does anyone with a similar battery/solar set up have experience with a Danfoss type refrigerator?

Does the Vitrifrigo dp2600i fit in the space where the 2662 is now?
Looking at the specs online it seems that it should fit but....

[Almot]

billtrev wrote:
The solar controller is curb side at the very front of the trailer along with the 12v positive and negative buss. The forward compartment were I could add batteries is adjacent to this. The 12v fuse block/converter is about five feet aft under a bed. The water heater is almost right behind the converter towards the outside wall.

You can add 2*100AH AGM to this forward storage. They are small ~7x12x9" WxLxH, total weight 100-125 lbs. You should be fine without reinforcing the floor. Or put a big piece of 3/4 ply to distribute the load. Or add one more joist.

Plus, another 2 or 3 of the AGM in the usual location on the tongue. I doubt these 2 added batts will overload your tongue too much - or you can use WD hitch.

[MEXICOWANDERER]

Need all new batteries and have a quandary about where to mount them? AGM batteries can go inside or outside and if their cost does not override consideration it is something to chew on. I can name several dozen million-dollar sloops and ketches that have AGM batteries under the skipper's bunk.

[billtrev]

The solar controller is curb side at the very front of the trailer along with the 12v positive and negative buss. The forward compartment were I could add batteries is adjacent to this. The 12v fuse block/converter is about five feet aft under a bed. The water heater is almost right behind the converter towards the outside wall.

The bottom of the trailer is enclosed by a "bellypan" with the tanks - fresh, gray, and black, starting just in front of the axles working forward.

Not much room under there but much thanks for the good idea.

The only place near the center of the trailer(front to back) would be under a street side bench seat. This would require a relatively long run of battery cables and put all the battery weight on one side of the trailer.

[westend]

Where is the solar controller and the 12V distribution panel in your rig?
When I restored my Starcraft, I chose to have the batteries as close to the distribution panel as possible. If you have no void space below/adjacent in a cabinet, there are battery racks that attach underneath the floor. If using those, AGM class would be my choice. Installing AGM on their side results in a height difference of 8". The two battery banks I have are located inside the TT, just forward of the axles on opposing sides. I already have a spot where I can add more batteries, just in back of the axles, inside.

[billtrev]

Thanks for all the replies, lots of good info here.

As of now we are leaning towards installing the Vitrifrigo and two Trojan T145's for 260 amp hr.

We would like to get away from the absorption fridge and its performance and safety issues. The cost of an automatic fire extinguisher (the dogs are at times alone in the trailer)and and ARP control on top of the price of a new 2662 would be more than a Danfoss 12v unit and still have marginal performance at best.

I would like to go with four GC-2 batteries but can't find a good place to mount them. The only place they would fit without extensive mods would be in a forward outside storage compartment. We would lose most of our outside storage and add about a 120lbs of tongue weight on top on the additional weight from upgrading from two group 24's to GC-2's.
The price of four good AGM's is also almost halfway to the cost of "homebrew" lithium setup.

Two Lifeline GPL-6CT's would give us 300 amp hr but they too would probably have to go in the same compartment...I can't raise the current battery box(it would interfere with the compartment door) and making it deep enough to hold the GPL-6CT would make it the lowest part of the trailer.

Which brings me back to the T-145's. I can fit these in the modified battery box and get a small increase in capacity at the cost of shorter life as compared to T-105's.

I might try to add two 100 watt panels to the topper of the tow vehicle on removable mounts so I could also use them a ground deployed array.

We'll shlep the Honda with us and hope to not have to use it too often.

If we find that we are constantly using the genny I guess I'll have to start saving for a 400 amp hr lithium battery bank. (after pricing these thing I know why they call it a bank...)

[EsoxLucius]

We have a Nova Kool RFU6800 12 VDC native compressor refrigerator that uses 60 to 80 AH a day depending on the outside temperature. You can see below our battery and solar capacity. Everything works well. I agree with good insulation and an exhaust fan. There is a 12 VDC circuit on the Nova Kool for a fan to run with the compressor.

[MEXICOWANDERER]

I you can modify the refrigerator hole, enlarge it, this is what I did. I clad the refrigerator in 2" rigid foam, then sprayed the condenser area as best I could with aerosol foam. It helped a lot. Both units are 24 vdc, more than twice the size of the largest double door gas refrigerator. The units average 41 amp hours at 24 volts each on the warmest days. The freezer unit is set to -5F and the refrigerator varies between 35 - 38F. Door shelf temp is close to 39F.

Inverters are not frugally electrically efficient. A true sine wave will keep the motor cooler but at best, expect 85% efficiency converting DC to AC. This is why I went with direct current. My bus can handle the tremendous weight of true energy efficient refrigeration.

[crosscheck]

We have 330 W solar, 4 AGM 6V batteries and a 7.5 cuft compressor fridge/freezer(NovaKool) and a Honda 2000W genny. Started out with 190w solar which was cutting it close when in warm conditions(85F). We dry camp almost exclusively and last time we used genny was in 2012. Just got back from a 7 day ttrip up North which was cool and cloudy. This was the first time in more than 5 years that we did not bring the Honda.

I think the key is having enough battery capacity to span those poor solar days if you want to go genny free. Right now my son has our Honda on a 10 day trip to Oregon. He has an older Bigfoot that only has 1 battery but has an absorbtion fridge but little other electrical requirements.No furnace use. But as he is dry camping, a genny is a requirement.

We all have different electrical requirements, yours maybe different from us as we tend to be on the conservative side but our fridge can use 20ahr or 75ahr/day depending on how warm the ambient temperature is. Generally, when the sun doesn't,t shine, day is cooler, less ahr from solar, but fridge electric consumption drops. Even when cloudy, your panels harvest some amps.

My recommendation is 4 batteries, conserve power by LED,s etc, drag along the Honda like we have for the last 5 years even if you don,t use it and have fun dry camping in any situation.

Dave

Nice thing about the compressor fridge is leaving for a 3 hour hike and not worrying about tubes getting damaged by out of level parking.

Bear Mt. Trailhead. Sedona.

[landyacht318]

What i really like about the danfoss/secop units is that one can easily run 0.5 amps of fans that cycle on and off with the compressor. Another fan to exhaust the heat generated by the cooling unit will greatly improve performance, compared to the cooling unit having only passive vents.

I upgraded my 120Mm compressor fan to a Noctua NF-f12 and moved it to the other side of condenser so it pushes air through it.

Duty cycle dropped instantly, along with noise and amp draw consumed by the fan.(The noctua is ~53cfm for 0.05amps)

The danfoss's compressor speed ( 2000 to 3500rpm) is controlled by the thermostat circuit. Add more resistance and the faster is spins and more amp draw is has.

My VF c51is came with a 270 ohm resistor to run it at ~2500 rpm. I removed it to run it at 2000 rpm. Extra insulation, and a 40MM low cfm low amp draw interior fan and the Noctua fan pushing air through condenser, once, with no chance of recycling preheated air, well this fridge performs awesome, cools stuff quickly, and rarely consumes more than 1Ah per hour.

This is only a 1.8 cubic foot fridge. I can't estimate battery draw on a larger fridge in another application/ installation.

I can say one can improve its efficiency greatly with a a little foresight regarding insulation and cooling unit ventilation, as opposed to just stuffing it in the cabinet as is.

[MrWizard]

Until I replaced several panels last yr
All the panels in my main array were unisolar, identical voltage, but different watts, and all in parallel
Yes they were all bought in different batches, but all were the same voltage specs
When I removed several to add three new 100w windy nation panels
I did get a slight voltage mis match
And yes there are converter losses, I still prefer our residential fridge over LP
I think the older smaller absorption fridge with push button piezo starter and No electronic controls worked much better than the new ones

[Almot]

Mr Wiz's system goes way back in the past. Panels were being added with time, mismatching is a byatch. Between this and inverter losses of 120V fridge, I would guess some 15-20% of energy is lost.

A lot depends on where you are. I'm shaking my head when snowbirds in desert are complaining that solar can't handle all their loads, so they need to run a genny once a day. No AC in daytime, no freezing temps in the night, hardly any rain, no shade. It can't get any better than that. With LP fridge a 300W flat solar will handle everything in these conditions, and they mostly have LP.

2*6V is marginal for long-term solar boondocking, even without compressor fridge. Doable with 400W, on a strict energy diet, and with LP fridge. Weekend stay is different.

[MrWizard]

675 amp hrs of agm batteries
679 Watts of solar panel
120vac residential compressor fridge

And I will not deliberately be without a generator
Full timers not weekend campers, that generator is essential auxiliary power

I will add that I like the idea of the Dan Foss type DC power variable speed compressor

And will get one someday

[wa8yxm]

I do not run solar but I have about 500 amp hours of battery.

I can, if boondocking, last longer than the "Quite Hours" at the area I stay on just battery.. one Danfoss type Freezer, One RV Absorption Fridge, Assorted devices running off an inverter (TV, Sat Receiver, Computers, DVR's) and more.

Try 9it.. If the sun don't shine fire up the Honda.. but try it, Might want to go 2 pair of GC-2.

[Almot]

Your bank is a small-ish. It will handle 4-6A of Danfoss, but it won't last long.

Roughly, expect to use close to 10 AH per 1 cu.ft. With 8 cf fridge you are looking at 70-80 AH daily. So - Westend is right, without sun you will have 1.5 days before the bank drops to 50%. With all other loads you'll need 100-120 AH, so - closer to 1 day. Roughly. Depends on the ambient.

400W solar, in NY? You'll harvest 130 AH on an average summer day. Not on the "best" day. And you will be using about that much. This is cutting too close. Have to agree with West, adding another 100-200W is desirable. Honda will help you out, but with 600W solar and (preferably) another pair of 6V, generator won't be needed.

Adding another pair of 6V, or (more expensive) replacing your 2*6V with 3*110AH of 12V, will not only extend you stay with "no sun", but it will also give you the benefit of shallow cycle. Bank will be closer to Full at all times, so you won't need too high charging current. Solar works every day, but it doesn't always generate high amps, as you've probably noticed.

You don't have to carry all the batteries in front. If you go AGM, it can be mounted inside if you have to. They are costly, but being able to do without a generator is worth something, IMO.