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Topic: Update: flexible solar and marine DC refrigerator operation (Read 771 times) previous topic - next topic

Update: flexible solar and marine DC refrigerator operation

I had a chance to do some testing on my solar and DC refrigerator in actual use.

My solar panels consist of two Uni-Solar PVL136 flexible panels, rated at 136 Watts each plus two Global Solar Power-Flex 90 Watt panels.  The reason for the mix is that my installer didn't follow directions when installing the Uni-Solar panels, leaving no room for more Uni-Solar panels.

In theory, I now have 136+136+90+90 = 452 Watts on my roof.  In theory, this could supply about 35 Amps at 13 Volts to the batteries, so it should be a good match to my 30 Amp MPPT charge controller.

Current wise, the panels are well matched, rated with short circuit currents of 5.1A and 6.3A.

Voltage wise, the panels (connected in series) are well matched to the MPPT controller, a Tracer-3215RN, having a maximum input voltage rating of 150 Volts.  Solar panel open circuit voltages are rated at 46.2+46.2+22+22 = 136.4 Volts, a good safety margin.

In actual operation, I have seen PV voltages as high as 126 Volts when the battery is fully charged and the charge controller not drawing any load from the panels.

I have yet to see the system under max power conditions, but once saw a peak of 26 Amps, so my belief is that with lower battery charge levels and good sun, the actual current into the batteries and coach might just get pretty close to 30A.

The refrigerator is a custom marine unit built by Sea Freeze to the same dimensions as my toasted OEM refrigerator.  It uses two Dan Foss 12 Volt only compressors, one for the upper freezer, one for the lower refrigerator.  I have a remote reading thermometer, and the temperatures never vary from 3 degrees in the freezer and 35 degrees in the refrigerator.

With both compressors running, the refrigerator draws 11 Amps.  I have no idea at this time what the duty cycle is.  11 Amps at 12 Volts is the same wattage as 1.1 Amps at 120 Volts in a domestic refrigerator, so I feel pretty good about this.  Plus, I don't need to run the power hungry inverter.

As a test, i turned of the AC charger, so my batteries are only getting charged by the solar panels, and discharged by the refrigerator and various parasitics.  Since the coach is stored next to my house, I am not using any other 12 volt devices.  I turned off the AC charger yesterday afternoon, with the Tri-Metric TM2020 saying the battery is FULL.  I went back and checked this afternoon, and the TM2020 still reads FULL.

This confirms one of my goals, to be able to take off on a cruise or the like with the coach in dry storage and the refrigerator running (with the generator set for auto start as insurance)

By the way, I am looking forward to putting this to the test in Quartzite come January.

Re: Update: flexible solar and marine DC refrigerator operation

Reply #1 –
Thanks for the update. It looks like your system is a reasonable upgrade after a failure of the "traditional" RV refrigerator. Your experience and measurements provide some good "real life" experiences. It will probably work well at Q in January. There should be lots of sun and mild temperatures.

I hope to see you again in January. If I make it to Q, it will probably be about January 21-24.

Re: Update: flexible solar and marine DC refrigerator operation

Reply #2 –
Looking forward to seeing you Tom so we can compare solar set ups.
JohnH

Re: Update: flexible solar and marine DC refrigerator operation

Reply #3 –
Be interesting in the actual consumption. You have enough solar to recharge a 200 amp hour draw down. 

For cloudy conditions and to possibly double battery life if it were my setup, which it isn't, I would try to adjust the battery capacity on board to not normally go much below 30% discharge. 

Some here have mentioned that upon removing their propane tanks they added a fourth gel 8d.

I would probably add a double second row where my three are.  Have to relocate the buss through the compartment divider wall in my case.

Like the dc idea.  Buddy with a new 42' tour with a normal household refer mentioned a 240  amp hour draw overnight with the inverter and lights and TV on....

Re: Update: flexible solar and marine DC refrigerator operation

Reply #4 –
I'm keeping the propane as is.  This is a U295 with a propane furnace and propane water heater.

I plan to keep an eye on the TriMetric and keep the battery level well above an indicated 50%, which is actually 75%.  This will require manual intervention as the generator autostart will never see the need to autostart when the sun is up, and would let the battery go to an actual 50% when the sun is down before auto starting.

Re: Update: flexible solar and marine DC refrigerator operation

Reply #5 –
Quote from: Tom Lang –
I'm keeping the propane as is.  This is a U295 with a propane furnace and propane water heater.

I plan to keep an eye on the TriMetric and keep the battery level well above an indicated 50%, which is actually 75%.  This will require manual intervention as the generator autostart will never see the need to autostart when the sun is up, and would let the battery go to an actual 50% when the sun is down before auto starting.

Not sure what the reference to 50% versus an actual 75% means?

Battery life is many times more at minimal draw down.  I know.  Sounds easy in a perfect world but expensive to buy extra batteries versus just buy new ones earlier as a set.

Going from 70-90% seems a reasonable compromise.  But I do not have a dc refer either.  And my food is not as cold either.

Re: Update: flexible solar and marine DC refrigerator operation

Reply #6 –
My Tri-Metric is set to read zero battery left when the battery is actually at 50%.  So a reading of 50% occurs when the battery is actually only 25% used.

My glass is always half full, or fuller.

Re: Update: flexible solar and marine DC refrigerator operation

Reply #7 –
I am new to the forum and I have been reading this topic. I like the calculated as well as the imperical engineering approch. I have done some very high capacity DC systems and I too believe in having the largest battery banks that the real estate will accommodate-without going overboard!  I like 6 volt and 2 volt deep cycle storage batteries. So, If you are looking for increased battery storage capacity, instead of taking things out of the coach maybe you can use batteries with about the same horizontal footprint but are taller vertically, two or four of the Trojan L16RE-A 325Ah 6 Volt would be one example, or if you really want to go wild try six of the Surrette S-1450 2 volts in series. It really depends on how much room you have and how the weight is distributed, and of course they are not cheap. Also, these are wet cell batteries and I don't know if that is what is used in FT or other coaches? Again, I am new to the forum and really getting a lot from it, but thought I would give something back-however useful it may be. Also, we think that a 2002-2004 FT 36' single slide with private head is the way we will be going, so we are looking.
Thanks
Bill

Re: Update: flexible solar and marine DC refrigerator operation

Reply #8 –
A couple of reasons why I plan to keep the batteries as they are:

1. I replaced all of my batteries about a year ago. It will be another six to ten years before they go. By that time, there might be new technology that will hold more power in less space and weighing less.

2. Foretravels coaches have best in class weight distribution right out of the box. I had my then 10 year old coach weighed for the first time last January,  and the fellow doing the weighing was astonished as to how close the weights were side to side and how much extra capacity I had in a fully loaded for travel coach. Adding battery weight without compensating will mess with success.

Re: Update: flexible solar and marine DC refrigerator operation

Reply #9 –
Going to add one or two 8d where propane is. Will either go with 20 lb tank or induction electric. Will add solar when I go full time.

Have one of last PA-22's off the line. Great value, ugly as sin. Tail wheel like yours way better

Re: Update: flexible solar and marine DC refrigerator operation

Reply #10 –
Quote from: nelo –
I am new to the forum and I have been reading this topic. I like the calculated as well as the imperical engineering approch. I have done some very high capacity DC systems and I too believe in having the largest battery banks that the real estate will accommodate-without going overboard!  I like 6 volt and 2 volt deep cycle storage batteries. So, If you are looking for increased battery storage capacity, instead of taking things out of the coach maybe you can use batteries with about the same horizontal footprint but are taller vertically, two or four of the Trojan L16RE-A 325Ah 6 Volt would be one example, or if you really want to go wild try six of the Surrette S-1450 2 volts in series. It really depends on how much room you have and how the weight is distributed, and of course they are not cheap. Also, these are wet cell batteries and I don't know if that is what is used in FT or other coaches? Again, I am new to the forum and really getting a lot from it, but thought I would give something back-however useful it may be. Also, we think that a 2002-2004 FT 36' single slide with private head is the way we will be going, so we are looking.
Thanks
Bill

Flooded cells maintenance, out gassing, and shorter service life would seem to be a step backwards for a hidden location battery bank.  Your stated years of interest have the batteries in a almost non access area I think.

Re: Update: flexible solar and marine DC refrigerator operation

Reply #11 –
Two days running on solar alone, and the trimetric still reports the batteries as full.

We'll see how it handles clouds.  It has been overcast the past few hours, and the weekend might bring rain.

Re: Update: flexible solar and marine DC refrigerator operation

Reply #12 –
I figured there might be a problem with wet cell's and I would agree that there are real disadvantages! 
Yep, PA-22 are odd looking but look real cool on the tail-they can kick your butt sometimes too!
Thanks
Bill
 

Re: Update: flexible solar and marine DC refrigerator operation

Reply #13 –
After three days and nights at Quartzite, it's time for a follow-up on this topic.

My 452 watts of solar on the roof, which should in theory provide 30A to my batteries, did reasonably well.  I have seen them pump out 25A in the summer, but were only good for 12-15 Amps at best in the winter.  Not enough to recharge the batteries daily, but enough to help.

Each 24 hour period saw my usable battery capacity diminish by about 30%.  After three days and nights, I was down to 10% and started the generator before starting the bug engine and hitting the road.  Remember, my floor is actually the 50% level according the battery specs.  Had I been staying longer, I could have run the generator every day or every other day, bring the battery up to 40% or 70% according to the battery monitor. Not bad.

Maybe in the summer, the solar would provide enough juice to keep the refrigerator going without use of the generator.

By the way, I kept the inverter off except to use the microwave or electric kettle, and didn't watch any TV.  I was also careful to only use the LED lights. Soon the halogens will all be gone. The refrigerator is keeping a constant 36 degrees F and the freezer a constant 3 degrees F.