Solar vs Residential Fridge

[Griswald One]

So I have to start with I am very solar knowledge deficient and my efforts to understand the math are so far very unsuccessful.

I am looking at a new unit that comes with a residential fridge. It also comes standard with a 100w solar panel and is upgradeable to 265w. There are 4 6V batteries on board. I don’t know the brand of battery but I assume they are whatever is industry standard.

My question is can the 265w solar system keep up with the demands of the fridge during storage? The fridge is a Samsung. I read that Grumpy’s Samsung is rated at 3.4amps, so I am hoping I would be in a similar range.

The unit also has a battery monitor and auto start on the generator so there is a backup if needed but I would not want to have that starting up every day just to keep the fridge going in storage.

Thanks in advance for your knowledge and suggestions.

[Grumpy]

Originally Posted by Griswald One

The fridge is a Samsung. I read that Grumpy’s Samsung is rated at 3.4amps, so I am hoping I would be in a similar range.

The label should be in the refrigerator section with the amp rating.

[Cannon]

Why do you want to keep the fridge on in storage.

[Griswald One]

Originally Posted by Cannon

Why do you want to keep the fridge on in storage.

Because i travel in the RV frequently but when I am home I have to put the RV in storage, normally for 7-10 days at a time. It means I have to empty the fridge everytime we come home. It also means I have to have storage space at home for the fridge contents. This unit also has an ice maker in the fridge that I will have to empty after each use.

It is small matter of convenience that will make my RV life a little bit easier. The upgrade is relatively inexpensive but I don’t really boondock so not a huge priority otherwise.

[Cannon]

Gotcha, I thought you were talking about long term winter storage.

[Nathan S.]

First off I’m not good at the math with these systems either. You need to know more about your batteries, that’s what is going to keep your fridge going. You also need an inverter because if I’m not mistaken a residential runs off AC. If you have enough amp hours in your batteries, and you have an inverter I can safely say a 100w solar panel is not going to keep up with a night of your fridge running off batteries. I’m not sure if 265w will do it either (here comes the math and battery capacity). You also have to consider weather. You get a couple of rainy days with that fridge running, you may do permanent damage to your batteries, that’s a $1,000. I think this is a bit of a tall order. But if you do want to do it, find an expert in solar installs. Your basically asking your rig to operate off grid 24/7.

[bdreinv]

Depends on sun shine we have one I think 300 watt 60 cell panel. Non residential frig not much help. I hear residential frigs are power hogs. May be trial and error let us know what you find out. Thanks

[JimD]

Inverters suck battery power, period. A quick rule of thumb is that the 120 volt current that is required will equate to about 10 times the amount of 12 volt current required. You can't pull power from thin air. Output power for 3 amps at 120 volts would equal 360 watts. Input 12 volt power for 360 watts would be 12 volts times 30 amps = 360 watts. Pulling 30 amps continuously from batteries will drain them in no time.

The only variable here is how often will the fridge require cooling. Since it will not be opened, the cooling unit may not need to come on very often depending on outside temp. When it does come on, the batteries will drain even with the solar putting out max power on a bright day. When not cooling the inverter will still have some drain on the battery.

I have 200 watts of solar that will not keep up with my battery drain when I use the inverter during the day to run my Direct TV equipment. I have a voltage/current monitor and can see almost 10 amps being pulled from the batteries (I have 2 12 volt). I watch the voltage slowly decrease if I run the TV all day.

200 watts of solar at best is good for only about 10 amps of charging current. That is basically under bright sun in the middle of the day with the sun directly overhead. I plan on adding another 100 watt panel to my rig.

In my opinion as an electronic technician, you will never be happy with a couple of batteries and some solar for a residential fridge. Remember, moon light and hazy days will not produce any solar power.

[Florida Ranger]

It would be easier to have an electric plug installed to plug coach into when you are home. Less to worry about. Even if you park it out in your yard.

[RVermont]

While it sounds great you really have to do the math on these. You will need significantly more solar and probably even more battery power. There is a great video on YouTube running through the math but not sure exactly what it was titled.

If you can get the math to work I would invest in a temperature recording device. At a minimum a unit that you could review when you get back to the unit to be sure the temps stayed in the safety range. Nothing worse then getting back to your rig thinking is okay and finding out the food got warm for a few days.

[mbell5263]

I ran the numbers on mine, and I determined I would need about 600w solar along with 4 or 6 batteries, can't remember which it was, just to keep it charged for approximately 5 days without running out of power.

[Griswald One]

Originally Posted by Florida Ranger

It would be easier to have an electric plug installed to plug coach into when you are home. Less to worry about. Even if you park it out in your yard.

Originally Posted by mbell5263

I ran the numbers on mine, and I determined I would need about 600w solar along with 4 or 6 batteries, can't remember which it was, just to keep it charged for approximately 5 days without running out of power.

I wish home plug in was an option, we live in a residential neighbourhood and have to keep the MH in storage between visits. Someday we hope to downsize the home and upsize the property to be able to park on site but that is not our reality today.

Thanks for those numbers, that is what I was looking for as it makes it clear that 265w is not going to be sufficient under any circumstance. It was a nice to have not need to have option.

[Vicr]

Originally Posted by Florida Ranger

It would be easier to have an electric plug installed to plug coach into when you are home. Less to worry about. Even if you park it out in your yard.

He said he keeps it in storage when he is home.

[Vicr]

Anything is possible with using solar to provide AC power. You need to spend the money on the solar panels, add a larger battery bank, increase the size of the inverter, add a solar controller, and run larger cables to the coaches roof from the solar controllers location plus all the additional labor involved to build this system. It can be done just takes money. I would take it to an RV shop that specializes in solar installations and get a quote.

[mbell5263]

Originally Posted by Griswald One

I wish home plug in was an option, we live in a residential neighbourhood and have to keep the MH in storage between visits. Someday we hope to downsize the home and upsize the property to be able to park on site but that is not our reality today.

Thanks for those numbers, that is what I was looking for as it makes it clear that 265w is not going to be sufficient under any circumstance. It was a nice to have not need to have option.

You might look at some other storage locations. I store mine and the storage has 110v outlet that allows me to plug it in to keep the batteries charged and will also run the refrigerator.

[RVermont]

I gave this some more thought and did some quick math. The 3.4 amp draw is 120 volts so that is 34 amps of 12 volt. Then this has to be inverted so say 10% loss so now you are at 37.4 amps per hour. The unit does not run full time so estimate 30 % or about 12 amps per hour or 288 amps per day. You have 4 6 volt batteries I would think about 400 amp hours which only 200 is available. So right there it would be difficult to make it one rainy day.

The math on solar is a completely different and complicated math calculation..

[NickMurabito]

Originally Posted by RVermont

I gave this some more thought and did some quick math. The 3.4 amp draw is 120 volts so that is 34 amps of 12 volt. Then this has to be inverted so say 10% loss so now you are at 37.4 amps per hour. The unit does not run full time so estimate 30 % or about 12 amps per hour or 288 amps per day. You have 4 6 volt batteries I would think about 400 amp hours which only 200 is available. So right there it would be difficult to make it one rainy day.

The math on solar is a completely different and complicated math calculation..

I had a residential Refrig in a other brand motorhome. I had 6 6 volt batteries, and 600 watts of solar. I never had a problem with my refrigerator not working when boon docking. While in Alaska, I left my rig in a campground with no hookups. When I returned 3 days later, all was well. How did I know this? I left a dish in the freezer with ice cubes. They did not melt, meaning the ice cubes stayed frozen, meaning I never lost power. You might contact AM Solar in Oregon. They installed my first system, and are great at helping with solar.

[kcordell57]

I had this same question about my residential fridge and I went to GoPower and asked them. Short answer, at least 800 watts of solar and 4 batteries, preferably lithium. With lithium you can go down to 20%, normal batteries only 50%. Costs to do it right came in anywhere from 5K to 10K. Remember, if you convert to lithium (about 3X the cost of a normal 12V battery), you have to have a lithium capable charger. You can't use the standard charger for normal 12V batteries.