Some ways to run a fridge on solar energy

[lorenzom]

I posted initially this in the show and tell forum, as it was an introduction to my builds. No pics, so it was moved here.

Now, here is my last (test only) build , just to demonstrate how it can be done with very current and simple stuff:

 

[GridWorks Green Solar]

I have no issues running a side by side fridge, small chest freezer,three quarter ton 120 volt mini split heat pump (Gopower IC3000 )
and a mini fridge off a new concept solar power system, if the sun is shining you can bet nothing is running on grid.
Seriously need the public to review what I spent the past seven years working on: https://diysolarforum.com/threads/n...olar-power-system-with-smart-switchers.48023/
Chased each problem down the rabbit hole till I made it work!
Under supervision of a licensed electrician and another tech.
Still buying gas and diesel??

 

[Tomthumb62]

2-Usual fridges work with the AC grid, and have a strong inrush current at start. If you want them to be run from an inverter, the inverter power will need to be oversized, could be by a 10 factor if not more.

Curious what you mean by a factor of 10? Do you mean that if the surge of a fridge startup is 900W, then one would need a 9000W inverter? That doesn't make sense, as our 800W surge works fine (until the battery gets low/voltage sag) on a 2000W inverter.

We have a 120V AC fridge "Avanti" brand that was highly raved about on RV solar forums. It draws 800W for 1-2 seconds when the compressor starts up, then instantly drops down to usually about 65-70W. I've seen it at 75W a few times and once as high as 90W, but usually around 65-70W.

Now when the fridge is first plugged in, it pulls 500-600W for about 5-8 seconds, then down to 0W, then in 2-5 minutes will do the normal cycle of 800W for 2 seconds, then 65-70W after that.

We have it plugged into a 2000W inverter. Usually no problems, but we have a gremlin either in our battery setup or cabling. I hope I now have the cabling fixed, I'll know in a few days when my wife returns to town with the trailer. And I think our battery gremlin is 1) not producing enough AH during daylight hours especially when traveling (flat roof mounted panels at 48-degrees north) and 2) not charging at high enough C-rate for a SLA battery bank, except when the AC charger is plugged in, which requires the generator (noise).

Now what I don't like about this fridge is there are zero fans in it. Using an infrared thermometer, with the fridge temp setting at 4 (midway), I will get 15-30F in the very back of the fridge, depending on where it is in it's cycle of cool/defrost. The items in the door will be about 38-40F and items in the shelves, even pushed back to the coldest back wall, will show 41-52F. Not a concern for me for camping for a few days or a week, but my food-sciences trained wife is growing grey hairs over this! I put a battery powered desk fan inside and it seems to help...a bit.

Since our system seems to be underpaneled and under-battery'd, I've thought about simply turning the inverter off overnight. Maybe crank the fridge temp up to 6 or 7 (the freezer got down to -20F when I turned it up to 7) in the latter part of the day to get it good and cold but while there's still sunlight out and then turn it down 2 hours before sunset and then shut it off 30 minutes before sunset. That's a lot of fussing around just to save some battery juice. We do have a generator, but the noise of it kinda defeats the point of the silence of solar. I doubt my wife would go for this plan, though, because likely the fridge internal temps would be in the 40's or 50's in the morning. This wouldn't fly or be safe in the hot days and nights of summer, but it could work in the shoulder seasons where the ambient temps are 70-80F in daytime and 30-50F at night.

Anyone else try or do this - turning off the fridge/inverter at night to save power?

 

[Charleswgibbs]

Curious what you mean by a factor of 10? Do you mean that if the surge of a fridge startup is 900W, then one would need a 9000W inverter? That doesn't make sense, as our 800W surge works fine (until the battery gets low/voltage sag) on a 2000W inverter.

We have a 120V AC fridge "Avanti" brand that was highly raved about on RV solar forums. It draws 800W for 1-2 seconds when the compressor starts up, then instantly drops down to usually about 65-70W. I've seen it at 75W a few times and once as high as 90W, but usually around 65-70W.

Now when the fridge is first plugged in, it pulls 500-600W for about 5-8 seconds, then down to 0W, then in 2-5 minutes will do the normal cycle of 800W for 2 seconds, then 65-70W after that.

We have it plugged into a 2000W inverter. Usually no problems, but we have a gremlin either in our battery setup or cabling. I hope I now have the cabling fixed, I'll know in a few days when my wife returns to town with the trailer. And I think our battery gremlin is 1) not producing enough AH during daylight hours especially when traveling (flat roof mounted panels at 48-degrees north) and 2) not charging at high enough C-rate for a SLA battery bank, except when the AC charger is plugged in, which requires the generator (noise).

Now what I don't like about this fridge is there are zero fans in it. Using an infrared thermometer, with the fridge temp setting at 4 (midway), I will get 15-30F in the very back of the fridge, depending on where it is in it's cycle of cool/defrost. The items in the door will be about 38-40F and items in the shelves, even pushed back to the coldest back wall, will show 41-52F. Not a concern for me for camping for a few days or a week, but my food-sciences trained wife is growing grey hairs over this! I put a battery powered desk fan inside and it seems to help...a bit.

Since our system seems to be underpaneled and under-battery'd, I've thought about simply turning the inverter off overnight. Maybe crank the fridge temp up to 6 or 7 (the freezer got down to -20F when I turned it up to 7) in the latter part of the day to get it good and cold but while there's still sunlight out and then turn it down 2 hours before sunset and then shut it off 30 minutes before sunset. That's a lot of fussing around just to save some battery juice. We do have a generator, but the noise of it kinda defeats the point of the silence of solar. I doubt my wife would go for this plan, though, because likely the fridge internal temps would be in the 40's or 50's in the morning. This wouldn't fly or be safe in the hot days and nights of summer, but it could work in the shoulder seasons where the ambient temps are 70-80F in daytime and 30-50F at night.

Anyone else try or do this - turning off the fridge/inverter at night to save power?

Cranking the temperature way down during the day and then turning off at night is a good strategy for coping with an excess of solar production and a lack of battery storage, as you are basically using the fridge as its own battery and storing energy that would otherwise go unused.

But if your problem is an overall lack of production I don't think it will help much. During the short time when solar is producing you'd just be putting that energy into your fridge instead of your battery.

You'd obviously use less power at night while turned off, but your battery won't be charged as much either since additional power is being diverted to the fridge. Basically energy consumption will be the same if you are maintaining the same temp, the difference would just be whether its used over a short or longer period of time.

 

[alfsauve]

lorenzom​

2-Usual fridges work with the AC grid, and have a strong inrush current at start. If you want them to be run from an inverter, the inverter power will need to be oversized, could be by a 10 factor if not more.

With newer appliances it seems that they tamed the inrush to a certain extent. I used an energy monitoring system, Emporia, on my circuit breaker box and this is what I found analyzing a new Samsung 28cuft SxS. The graph is taken from by the second measurements. Rather than run full out it appears they have at least 2 levels of cooling. I think the message is know your appliances.

 

[TomC4306]

That is my experience also.

 

[Risky Rob]

How much power does your fridge draw? I don't see you mention "inverter-type" fridge. Ours is inverter-type 8 cu. ft., max draw rated is 85w, hooked up to our 1kw 12v 150Ah portable AIO, only draws around 50w at normal setting.

I have a 12 year old energy star GE and the interior plate "says" 750W, but it is usually drawing more like 150W.

 

[alfsauve]

I had a devil of a time finding the actual draw on my Whirlpool Dryer. it’s not in the specs. The installation guide says use a 30A breaker but I know that’s excessive. I chatted with a support specialist who “confirmed“ it was 30A. After I installed Emporia and recorded the draw I found it was actually only 9A max at any time with again a fairly low inrush. plus they pulse the dryer coils, sort of a crude PWM, and don’t have them running full blast continuously.

 

[Checkthisout]

I had a devil of a time finding the actual draw on my Whirlpool Dryer. it’s not in the specs. The installation guide says use a 30A breaker but I know that’s excessive. I chatted with a support specialist who “confirmed“ it was 30A. After I installed Emporia and recorded the draw I found it was actually only 9A max at any time with again a fairly low inrush. plus they pulse the dryer coils, sort of a crude PWM, and don’t have them running full blast continuously.

The sampling rate of your measuring equipment is probably not fast enough to catch the LRA of the dryer motor.

 

[Checkthisout]

My 3000 watt AIMS inverter makes 6000 watt surge and has an idle draw of about 12 watts.

My 20 year old fridge draws about 1.8Kwh per day when started from ambient then goes down to about 1.2-1.5. (lots of variability here).

 

[Tomthumb62]

My 3000 watt AIMS inverter makes 6000 watt surge and has an idle draw of about 12 watts.

My 20 year old fridge draws about 1.8Kwh per day when started from ambient then goes down to about 1.2-1.5. (lots of variability here).

I looked up their 1500W version. It draws only 9.6W at idle. Our 2000W Renogy draws 24W at idle. When battery capacity is short supply, that adds up quick!

The only thing I don't like about the AIMS model is the USB output is limited to 1A, which is very small and it takes forever to charge a phone at 1A. 2.4A is the norm these days. Surely a 2.4A vs. 1A USB outlet can't be the difference in idle consumption? Otherwise, I would consider selling our Renogy and switch to the AIMS.

 

[Checkthisout]

I looked up their 1500W version. It draws only 9.6W at idle. Our 2000W Renogy draws 24W at idle. When battery capacity is short supply, that adds up quick!

The only thing I don't like about the AIMS model is the USB output is limited to 1A, which is very small and it takes forever to charge a phone at 1A. 2.4A is the norm these days. Surely a 2.4A vs. 1A USB outlet can't be the difference in idle consumption? Otherwise, I would consider selling our Renogy and switch to the AIMS.

I tried the Renogy 3k to save some money and didn't do half of the AIMS is capable and kept throwing false ground faults.

I am sure the AIMS isn't the benchmark for quality but it packs a serious punch. I can run the 1500 watt micro and exhaust fan, the fridge can be running along with a few hundred other watts of draw it will still start the dryer with barely any voltage sag. Neat.

Just get a plug-in USB charger or one for like a car and use that. I don't utilize the USB charger on the face inverter. It's down in a compartment and I can just plug in the ordinary household chargers into the outlets it's powering. Most built-in usb chargers on things don't work with the new phones anyway. Too many amps.

 

[Nevadablue]

I just ordered a 10 amp down converter to give me 12 volts from my new 24 volt system. It will power 12 volt outlets for any of those goodies that need it, including the USB outlets. It will be switched to allow it to be OFF when not in use.

https://www.amazon.com/gp/product/B07V6X6L89/ref=ox_sc_act_title_3?smid=A3GYM455B71YGR&psc=1

 

[Tomthumb62]

I tried the Renogy 3k to save some money and didn't do half of the AIMS is capable and kept throwing false ground faults.

I am sure the AIMS isn't the benchmark for quality but it packs a serious punch. I can run the 1500 watt micro and exhaust fan, the fridge can be running along with a few hundred other watts of draw it will still start the dryer with barely any voltage sag. Neat.

Just get a plug-in USB charger or one for like a car and use that. I don't utilize the USB charger on the face inverter. It's down in a compartment and I can just plug in the ordinary household chargers into the outlets it's powering. Most built-in usb chargers on things don't work with the new phones anyway. Too many amps.

Good point on just using an AC usb charger, a decent one.

Now I'm looking at the AIMS 1500W inverter-charger. Wish I could justify the expense, as we do need a better charging system for our AGM batteries. They don't get enough charge (too low amps) on solar and our AC charging system is a bit too underpowered as well. The inverter-charge model I was looking at also has an eco low-idle switch, which draws 8w compared to 11.5. Would be the perfect solution to our setup.

I do love most of our Renogy gear. It's fairly well-designed, both functionally, user interface and asethically, decent price and quality is good enough for our light use. But the inverter isn't one of them, I wish we had chosen different.

 

[Risky Rob]

I looked up their 1500W version. It draws only 9.6W at idle. Our 2000W Renogy draws 24W at idle. When battery capacity is short supply, that adds up quick!

The only thing I don't like about the AIMS model is the USB output is limited to 1A, which is very small and it takes forever to charge a phone at 1A. 2.4A is the norm these days. Surely a 2.4A vs. 1A USB outlet can't be the difference in idle consumption? Otherwise, I would consider selling our Renogy and switch to the AIMS.

I bought a specialized inverter made for my 40V power tool batteries ($40) and have 2 usb (2A) outlets and a standard 110V AC outlet. I used it along with my big solar inverter during the California Flex Alerts.

https://www.amazon.com/dp/B01MZACMQ1?ref=nb_sb_ss_w_as-reorder-t1_ypp_rep_k1_1_10&amp=&crid=38CTYV1564PPF&amp=&sprefix=greenworks

 

[acdoctor]

My 10 cf 120 volt fridge in the RV developed a leak in the evaporator.
I replaced it with a 12 volt inverter model. It uses about 0.5 kw per day. It also allows me to turn off the inverter. Now I only turn the growatt on when I need it.
New fridge cost about 3 times the price of a 120 volt model but I can only fit 2 kw of panels on the roof.

 

[Checkthisout]

My 10 cf 120 volt fridge in the RV developed a leak in the evaporator.
I replaced it with a 12 volt inverter model. It uses about 0.5 kw per day. It also allows me to turn off the inverter. Now I only turn the growatt on when I need it.
New fridge cost about 3 times the price of a 120 volt model but I can only fit 2 kw of panels on the roof.

Which one did you get and does it auto defrost etc?

Lots of RV's are just going to residential fridges. I assume they can be either ac or dc

You can run them while driving (not that we didn't run the propane one while driving), they cost less, are way cheaper to install, have more room and auto defrost. Auto defrost is important for efficiency and convenience..at least that's how I feel.

 

[Tomthumb62]

Which one did you get and does it auto defrost etc?

Lots of RV's are just going to residential fridges. I assume they can be either ac or dc

You can run them while driving (not that we didn't run the propane one while driving), they cost less, are way cheaper to install, have more room and auto defrost. Auto defrost is important for efficiency and convenience..at least that's how I feel.

Yes we went with an AC fridge. Compressor uses 800W for 1-2 seconds on startup and 65-75W typical the rest of the time.

The thing many people overlook is the idle draw of their inverter. Some pull 45-100W. Our 2000W 12v Renogy inverter uses 24W. I'm looking at an AIMS 1500W inverter-charger that uses 11W idle and has an eco idle switch that only uses 8W.

24W constant draw is 576Wh a day! Our tiny trailer solar system struggles to keep up with powering the fridge, inverter and other stuff like lights, pump. So only using 8W is 192Wh a day, which is 3x less! Only problem is having to sell the Renogy inverter to justify the $$$ of the AIMS device.

 

[acdoctor]

Which one did you get and does it auto defrost etc?

Lots of RV's are just going to residential fridges. I assume they can be either ac or dc

You can run them while driving (not that we didn't run the propane one while driving), they cost less, are way cheaper to install, have more room and auto defrost. Auto defrost is important for efficiency and convenience..at least that's how I feel.

It’s a Everchill from Recpro. It does have 120 watt automatic defrost. Freezer seems to max out at 0 deg F. Just like any fridge it draws higher watts while cooling down from room temperature.

 

[Checkthisout]

Yes we went with an AC fridge. Compressor uses 800W for 1-2 seconds on startup and 65-75W typical the rest of the time.

The thing many people overlook is the idle draw of their inverter. Some pull 45-100W. Our 2000W 12v Renogy inverter uses 24W. I'm looking at an AIMS 1500W inverter-charger that uses 11W idle and has an eco idle switch that only uses 8W.

24W constant draw is 576Wh a day! Our tiny trailer solar system struggles to keep up with powering the fridge, inverter and other stuff like lights, pump. So only using 8W is 192Wh a day, which is 3x less! Only problem is having to sell the Renogy inverter to justify the $$$ of the AIMS device.

If you already have a converter (rv battery charger) just get a normal aims 2000 watt psw inverter.

The aims inverter chargers are kinda spendy and I don't believe they offer any special features like victron multipluses such as surge using both gen and battery juice etc.

You might also just look at an even more tiny inverter strictly for the fridge.

Have you done any advanced electrical investigation and seen if your ac fridge actually has a DC compressor and what voltage it requires?

 

[Tomthumb62]

If you already have a converter (rv battery charger) just get a normal aims 2000 watt psw inverter.

Might just do that. Except we need a better charging system for our AGM batteries. Current method is very bulky and my wife doesn't like tripping over large AC chargers, lol.

The aims inverter chargers are kinda spendy and I don't believe they offer any special features like victron multipluses such as surge using both gen and battery juice etc.

Good to know. Wasn't really planning on it, not quite in the budget for an RV. Getting a little obsessed with this stuff for how little we use it!

You might also just look at an even more tiny inverter strictly for the fridge.

Not a bad idea either. A 700W inverter would suffice, since the fridge only pulls 800W for 1-2 seconds. When it's first plugged in, it pulls 500-600W for about 5-10 seconds, then shuts off.

Have you done any advanced electrical investigation and seen if your ac fridge actually has a DC compressor and what voltage it requires?

No, I haven't. You saying it might be possible to directly wire our fridge's compressor to the battery (fused of course)? Or perhaps with some small voltage converter? That would be awesome!

 

[Checkthisout]

Might just do that. Except we need a better charging system for our AGM batteries. Current method is very bulky and my wife doesn't like tripping over large AC chargers, lol.

Good to know. Wasn't really planning on it, not quite in the budget for an RV. Getting a little obsessed with this stuff for how little we use it!

Not a bad idea either. A 700W inverter would suffice, since the fridge only pulls 800W for 1-2 seconds. When it's first plugged in, it pulls 500-600W for about 5-10 seconds, then shuts off.

No, I haven't. You saying it might be possible to directly wire our fridge's compressor to the battery (fused of course)? Or perhaps with some small voltage converter? That would be awesome!

Maybe. Or you could use the thermostat (if manual) to turn the inverter on and off. That sort of thing. When fridge calls for cold, inverter switches on etc.

That requires tinkering though.

 

[Tomthumb62]

Maybe. Or you could use the thermostat (if manual) to turn the inverter on and off. That sort of thing. When fridge calls for cold, inverter switches on etc.

That requires tinkering though.

Thanks a good idea. Would require opening up the inverter to wire that in. Have to check to see if I'm out of warranty yet lol.

Only issue with that is when the fridge is first plugged in, it always draws about 600W for about 10 seconds. If that happened several times a day, it might negate the savings of just having the inverter run 24/7. I think a smaller inverter (or at least with a lower idle draw) is the best bet overall.

 

[sunsurfer]

Indeed.

But do you really want to be one of the first folks to put a butane-based refrigerator in a kitchen near a stove?

I'd be happy with it for an outdoor fridge but I'm not all warm and fuzzy thinking about using one in a kitchen.

legally in the USA, I think it is just an ounce or so max allowed. I prefer hydrocarbon refrigerants. They are super efficient and move oil very well through the system. Every custom system I have built has been either propane(R290) or butane(R600a). They work very well. If you design it right, you can go with very small charges. Not enough to do any thing with a leak.

They have been used all over the world for many years without problems. The USA like usual is behind. Our problem is the big lobby forcing us into DOW chemical patented refrigerants that we all pay for at a premium $$$$.

 

[efficientPV]

When looking up fridges, I have noticed several comments that say the R600 refrigerators are not to be used in garages. Lawyers are over sensitive to some car driving into them.