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Old 12-16-2017, 07:57 PM   #1
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New RV - Solar System Advice

Hi folks. We are soon taking possession of our new Sierra 372LOK 5th wheel. This RV has the new 20cuft residential refrigerator with 1000 watt inverter, hence the reason for this post.

This will be the first RV we have owned with this type of fridge and our concern is keeping it powered when not on AC hookup or generator for extended periods.

Currently we occasionally camp at parks however the new RV will primarily be used at our RV property which has no power. Our goal is to have a solar system that can power the fridge when we are not there, typically from Monday to Friday. Once the weekend comes we dont mind having to run the generator to power the RV if we have to.

I've done some research and I know I will need to upgrade the batteries to some good 6V units to make this happen. So the intent now is to add four 6 volt GC batteries at say 235 AH each wired in a series parallel connection for 12 VDC supply. What I need advice on is how many panels of what size will i need to keep these batteries charged to accomplish this.

The refrigerator is an LG energy star rated unit and according to LG website it uses 536 KWh per year......if this helps.

Please comment with any advice and also please ask if you need any further info.

Thanks
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Old 12-16-2017, 08:28 PM   #2
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Where is your property located?
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Old 12-16-2017, 08:29 PM   #3
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Where is your property located?
Newfoundland, Canada.
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Old 12-16-2017, 08:34 PM   #4
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Newfoundland, Canada.
And we only use the RV from mid May to mid Sept.
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Old 12-16-2017, 09:33 PM   #5
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Interesting problem.
536 KWH per year calculates to about 1500 watt-hours per day, I believe.
Assuming 90% inverter efficiency and no other load, calculates to about 1670 watt-hours per day, I believe.
Your four 235 amp hour 6 volt batteries, following the "don't discharge below 50%" recommendation and series/parallel connected for 12 volts, will give you 235 amp-hours at 12 volts or about 2800 watt-hours when fully charged - so a little over a day and a half of refrigerator operation.
On those assumptions and calculations, you would need to replenish about 1700 watt-hours per day, on average, from your solar system. E.g., 500 watts of panels, 6 hours sun per day, 60% total system efficiency (sun alignment, shadows, clouds, charge controller efficiency, etc.).
Note, the 1 1/2 day battery capacity when fully charged doesn't give much room for averaging - a few cloudy days in a row could result in your batteries being discharged to below 50%.
May well be that the refrigerator uses less energy than indicated during periods when you are away and don't open the fridge doors.
Lithium Ion batteries (big $s) can be discharged their full rated capacity without being damaged.

Just my thoughts -
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Old 12-16-2017, 09:47 PM   #6
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With those batteries, two ~300w panels and a good charge controller will run your fridge and lights forever.
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Old 12-16-2017, 10:00 PM   #7
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1000w setup and do lithium batteries with built in battery management system (bms). 4 100ah lithiums.and.you will be good.
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Old 12-16-2017, 10:27 PM   #8
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1000w setup and do lithium batteries with built in battery management system (bms). 4 100ah lithiums.and.you will be good.

I do love my Battle Born lithium batteries!

http://learntorv.com/battery-upgrade/
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Old 12-17-2017, 06:41 AM   #9
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Interesting problem.
536 KWH per year calculates to about 1500 watt-hours per day, I believe.
Assuming 90% inverter efficiency and no other load, calculates to about 1670 watt-hours per day, I believe.
Your four 235 amp hour 6 volt batteries, following the "don't discharge below 50%" recommendation and series/parallel connected for 12 volts, will give you 235 amp-hours at 12 volts or about 2800 watt-hours when fully charged - so a little over a day and a half of refrigerator operation.
On those assumptions and calculations, you would need to replenish about 1700 watt-hours per day, on average, from your solar system. E.g., 500 watts of panels, 6 hours sun per day, 60% total system efficiency (sun alignment, shadows, clouds, charge controller efficiency, etc.).
Note, the 1 1/2 day battery capacity when fully charged doesn't give much room for averaging - a few cloudy days in a row could result in your batteries being discharged to below 50%.
May well be that the refrigerator uses less energy than indicated during periods when you are away and don't open the fridge doors.
Lithium Ion batteries (big $s) can be discharged their full rated capacity without being damaged.

Just my thoughts -
Yes interesting problem indeed. Its no big deal i guess if we cant achieve this as we just pack everything up before we head home each Sunday or Monday. It would just be nice now that we have a big fridge to keep some stuff there...especially considering this fridge is rather big thus will take some time to cool once we get there say on a late Friday afternoon.

One point that I did actually did consider is that the fridge should consume less energy with the RV unoccupied.

Well thanks for the legwork, it looks like I will need a bigger system than i thought. Was really hoping that a 200 watt system would do it.

Maybe I will try a 200 watt system than add panels if required.

With that said can anyone recommend the components I need. I know I can get Renogy on amazon.ca, is this a brand that is that is considered to be of decent quality.
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Old 12-17-2017, 06:42 AM   #10
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I do love my Battle Born lithium batteries!

Let’s Boondock! Battery upgrade (to lithium)! | Learn To RV
Dont have the budget for Li batts.
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Old 12-17-2017, 06:44 AM   #11
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Also.....forgot to mention that Newfoundland is not exactly the sunshine state either...lol
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Old 12-17-2017, 07:19 AM   #12
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Also.....forgot to mention that Newfoundland is not exactly the sunshine state either...lol
Then you would want to double your solar capacity
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Old 12-17-2017, 07:32 AM   #13
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Even with bigger batts you may be doomed to dead batts.

The home fridge manufacturers do not count the heater strips on the door seals or he insulation heaters in their use calculations.

As most house units are bought on internal volume , thin insulation is required for the biggest measured internal volume .

This thin insulation gets wet and must be dried often to be effective.

Some cash spread on K street made the failure to count the total electric use.

A better insulated fridge might be one solution, Sun Frost has good insulation and excellent more efficient DC cooling components.

These are large and expensive.

Plan B might be a change over to a proper propane fridge,

Plan C might be a really fine large battery charger and a few hours a day of heavy charging with the noise maker.

First though , before any changes are made would be a Kill a Watt measuring device to see what power is really required.

And if you insist on DC a SOC ,( state of charge ) meter should be installed , to show the condition of the battery set .

And don't forget for solar to function you must avoid trees and shade and park in direct sunlight.
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Old 12-17-2017, 09:29 AM   #14
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Bottom line is that you will need around 800 watts of solar panels, not flat but angled at something around 20 degrees and pointed due south. Long term, batteries don't matter as they only allow you to get through the night and let you live through a couple of bad solar days. Four lead acid deep cycles will give you at least 24 hours without any sun but six would be better.

Your reefer will average draw around 100 watts continuously. I know this since I have measured my Frigidaire which is almost identical. I didn't open the door during my tests either and had the icemaker shut off. Average ambient temperatures were in the mid 70's.

I calculated your solar output using St. Johns as the location, but wherever you are in Newfoundland should be close. You will need at least 2.4 kWh each day and the 800 watt system would produce 3.53, 3.64, 3.72, 2.75, 2.52 (kWh per day...May to September.) The numbers are a little higher since the load numbers did not include battery charging efficiencies.

You could try and get away with 600 watts, but remember, there is nobody there when the inverter cuts out from low voltage...

I am sure this is more than you expected...but that's the real scoop on solar and Newfoundland is not an ideal location for this technology.
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Old 12-17-2017, 10:26 AM   #15
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Originally Posted by FFred View Post
Even with bigger batts you may be doomed to dead batts.

The home fridge manufacturers do not count the heater strips on the door seals or he insulation heaters in their use calculations.

As most house units are bought on internal volume , thin insulation is required for the biggest measured internal volume .

This thin insulation gets wet and must be dried often to be effective.

Some cash spread on K street made the failure to count the total electric use.

A better insulated fridge might be one solution, Sun Frost has good insulation and excellent more efficient DC cooling components.

These are large and expensive.

Plan B might be a change over to a proper propane fridge,

Plan C might be a really fine large battery charger and a few hours a day of heavy charging with the noise maker.

First though , before any changes are made would be a Kill a Watt measuring device to see what power is really required.

And if you insist on DC a SOC ,( state of charge ) meter should be installed , to show the condition of the battery set .

And don't forget for solar to function you must avoid trees and shade and park in direct sunlight.
Plan B and C is not an option.

There is no shade at all so thats one bonus.
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Old 12-17-2017, 10:35 AM   #16
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Originally Posted by FFred View Post
Even with bigger batts you may be doomed to dead batts.

The home fridge manufacturers do not count the heater strips on the door seals or he insulation heaters in their use calculations.

As most house units are bought on internal volume , thin insulation is required for the biggest measured internal volume .

This thin insulation gets wet and must be dried often to be effective.

Some cash spread on K street made the failure to count the total electric use.

A better insulated fridge might be one solution, Sun Frost has good insulation and excellent more efficient DC cooling components.

These are large and expensive.

Plan B might be a change over to a proper propane fridge,

Plan C might be a really fine large battery charger and a few hours a day of heavy charging with the noise maker.

First though , before any changes are made would be a Kill a Watt measuring device to see what power is really required.

And if you insist on DC a SOC ,( state of charge ) meter should be installed , to show the condition of the battery set .

And don't forget for solar to function you must avoid trees and shade and park in direct sunlight.
Most modern reefers use foam insulation as it is far more efficient on thin walls. It does not get wet. Door seal heaters and defrost heaters are carefully controlled by the microprocessor and never overlap with the high load periods.

Bottom line is that a simple test on a Kill a Watt will only give you instantaneous draw. Modern reefers are far more complex than old units and use inverter compressors which draw continuously but with a variety of specific loads. Accurately measuring one requires good long term data over at least 10 hours or more. My Frigidaire will draw 600 watts, 120 watts and 60 watts during its cooling cycle. Long term average load is around 100 watts at reasonable ambient temps but you will never see that with a single measurement.
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Old 12-17-2017, 10:36 AM   #17
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Renogy panels are good quality. I have a portable 100 watt set that I use for topping up when I am off grid. I am going to get roof top 300 watts... eventually.

As far as sizing, more is better, I consider 200 watts is the bare minimum for a normal RV where you can run the fridge on LP. I would seriously consider swapping out your fridge for the dual LP/Electric version. Then put solar panels in to keep the batteries topped up to power the 12 volt controls for the LP system. That or shutting EVERYTHING including the batteries down when you leave. There are a lot of 'phantom' loads in these rigs that can pull batteries down in a hurry.

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Old 12-17-2017, 11:24 AM   #18
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Your disadvantage is the location, you don't get the sunshine hours you need to set up a system efficiently but the advantage is you don't have to place the panels on your roof. You need to find out what the optimal angle is to the sun and then place the panels accordingly. IMO, what you could do is either buy 24 Volt panels or connect 12 Volt panels in groups of 2 (in series) for higher Voltage output, you need more than 12 Volt to charge your batteries and you may not get enough sunshine in your area to get that out of a single 12 Volt panel when connected in parallel.
When we started with solar and a residential fridge we found that our 480 Watt system was borderline, we then upgraded to 960 Watt and are safe now, even here in the Rockies.

It is important to have at least 600 AH nominal battery storage, more is better to make it through cloudy days. Also, you will need good deep cycle batteries, not the hybrid batteries they stick in the rv's. Golf cart batteries or deep cycle AGM batteries are a good choice.

If it was me, I would lay out the wiring for at least 1000 Watt solar, start with 600 Watt capacity and connect groups 2 panels in series and hook them up to a 40 Amp MPPT solar charge controller. There are a number of respected brands on the market.
If this setup is not sufficient, you can always connect one more pair of panels or start a 2nd solar array.
You can find wiring calculators on the internet, I use the calculator from Southwire.

Bottom line is, the initial setup is very expensive and don't expect the system to pay for itself, we are not in the US and Canadian prices are ridiculous in comparison, but when done right you will be in for a treat. We can run our washer and dryer on a good summer day.
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Old 12-17-2017, 11:44 AM   #19
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New RV - Solar System Advice

I know of other engineers who have run the 1000w Honda 24/7 to power sensors and other small equipment. The thing fits in a small box and is whisper quiet. Lots of people, including myself, have run the 2000 while driving. Mine from the bed of the truck.

The 1000 will run your whole trailer, other than hvac, and is about the size of two six volt batteries.

Getting off the grid 100% is expensive.

Another option is a smaller chest fridge. Far more efficient.
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Old 12-17-2017, 01:38 PM   #20
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I know of other engineers who have run the 1000w Honda 24/7 to power sensors and other small equipment. The thing fits in a small box and is whisper quiet. Lots of people, including myself, have run the 2000 while driving. Mine from the bed of the truck.

The 1000 will run your whole trailer, other than hvac, and is about the size of two six volt batteries.

Getting off the grid 100% is expensive.

Another option is a smaller chest fridge. Far more efficient.
AS mentioned we have no issue running our 2000i Yamaha on days while we are there.....we've been doing that for years with our last RV. Our new RV has the residential reefer and can hold alot more food....thus we are tossing around the idea of leaving food there while we are away, mostly Monday to Friday.

Not interested in driving to the RV every day to refill the generator or running an aux fuel tank. But thanks all the same.
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