# Solar Powered Deep Freezer Fridge

Registered Users Posts: 21✭✭
Here is the plan:
15 Cubic foot Freezer Converted to Fridge
1000w Pure Sine Inverter (Tripp Lite)
320w Solar Panels
4 each 6 volt batteries

no charge controller yet

looking at 30A controller MPPT

Any thoughts??

edited August 2016 #2
For a standard fridge/freezer--The 1,000 Watt inverter may or may not reliably start the compressor--Typically, 1,200 to 1,500 Watt is recommended for reliable compressor operation.

And, we do not know how much energy the freezer will use as a refrigerator... Just to be relatively conservative, lets guess 500 WH per day. 2 days of storage, and 50% maximum discharge (longer battery life) on a 12 volt battery bank:
• 500 WH per day * 1/0.85 AC inverter eff * 2 days storage * 1/0.50 max battery discharge * 1/12 volt battery bank = 196 AH @ 12 volt battery bank
So--While you should be able to run with a 200 AH @ 12 volt battery bank (2x 6 volt @ 200 AH golf cart batteries)--With a flooded cell battery, I would recommend a 480 AH @ 12 volt battery bank to support ~1,200 Watt starting load (AGM can use the 200 AH @ 12 volt battery bank).

Suggest 5% to 13% rate of charge for battery bank--And 10% or more for full time off grid (vs weekend/seasonal system usage). The solar array for such a battery bank would be:
• 480 AH * 14.5 volts charging * 1/0.77 panel+controller deratings * 0.05 rate of charge = 452 Watt array minimum
• 480 AH * 14.5 volts charging * 1/0.77 panel+controller deratings * 0.10 rate of charge = 903 Watt array nominal
• 480 AH * 14.5 volts charging * 1/0.77 panel+controller deratings * 0.13 rate of charge = 1,175 Watt array "cost effective" maximum
Note, the larger the battery bank, the larger the suggested minimum array.

Then there is sizing array based on energy usage and by season... You did not say if this was for backup power, full time off grid, inside or outside, generator backup, other power usages (LED lighting, cell phone charging, laptop computer, etc.)... A nominal system design would look like (assuming Missoula Montana):

### MissoulaAverage Solar Insolation figures

Measured in kWh/m2/day onto a solar panel set at a 43° angle from vertical:
(For best year-round performance)
 Jan Feb Mar Apr May Jun 2.66 3.75 4.71 5.12 5.13 5.41 Jul Aug Sep Oct Nov Dec 6.11 5.90 5.20 3.93 2.86 2.37
Normally, toss the bottom three months (assume generator use for bad weather--And for a refrigerator out on the back porch, energy usage may fall in freezing weather), pick February as "break even month":
• 500 WH per day * 1/0.52 off grid system eff * 1/3.75 Hours of sun per Feb day = 256 Watt minimum array (Feb break even)
If, you expected 500 Watts per day, and little to no genset backup, then you should run daily power usage to 65-75% of designed power output (to allow for some bad weather), and if you pick December as break even month:
• 500 WH per day * 1/0.65 daily power usage * 1/0.52 off grid system eff * 1/2.37 Hours of sun per Feb day = 624 Watt array minimum (12 months per year)
If we go back to suggested minimum solar array for battery bank (based on starting surge current), it was ~903 Watt array for 10% rate of charge with a 1,200 Watt minimum AC inverter....

So--Without knowing much about where you are located, if you will use genset for winter/bad weather, etc... At this point, I would be suggesting a ~903 Watt minimum array (note, solar math is not that exact.... I am using 903 Watts so you can see where I am pulling the numbers from -- Anything within ~10% is pretty much "exact" in solar power estimate).

And possibly a larger AC inverter (1,200 Watts minimum)... It is possible that your 1,000 Watt Tripplite will work fine for you--I just do not know.

Also, with a 903 Watt array--You will have lots of extra power for much of the season...
• 903 Watt array * 0.52 off grid AC system eff * 3.75 hours of sun (9 months of the year) = 1,761 Watt*Hours per day
That is enough to keep a cabin well lite and the folks entertained (laptop, cell phone, LED TV) and probably a 12 volt RV water pump for plumbing (surface water, or use deep well pump + cistern + genset or a "solar friendly" deep well pump).

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Solar Expert Posts: 295✭✭✭
Bosch A+ fridge and freezers work perfectly on small inverters. Draw about 90w a day depending on use.
5kVA Victron Multiplus II, 5.2kW array, 14kWh DIYLifepo4 bank, all grid-tied.

• Solar Expert Posts: 1,386✭✭✭✭
edited August 2016 #4
When using solar, it's usually best to buy the highest efficiency appliance possible. So in the case of EU rated appliances, I'd buy A+++. In the US, something Energy Star rated.

Consider buying the freezer somewhat larger than needed (it doesn't add much to the energy usage) and then fill all the unused space with water jugs. This should allow turning it off for significant periods (perhaps 3am to 9am), saving some wear on the batteries and generator.

I am available for custom hardware/firmware development

• Solar Expert Posts: 3,830✭✭✭✭
My brand new 14 cubic foot Danby freezer showed a 220 watt start up surge for ~1/2 second. Things have changed.

However...wattage while running varies a bit. Didn't expect that. Up to 80 watts while running. Only had it a week.
First Bank:16 180 watt Grape Solar with FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
• Registered Users Posts: 21✭✭
BB. said:
For a standard fridge/freezer--The 1,000 Watt inverter may or may not reliably start the compressor--Typically, 1,200 to 1,500 Watt is recommended for reliable compressor operation.

And, we do not know how much energy the freezer will use as a refrigerator... Just to be relatively conservative, lets guess 500 WH per day. 2 days of storage, and 50% maximum discharge (longer battery life) on a 12 volt battery bank:
• 500 WH per day * 1/0.85 AC inverter eff * 2 days storage * 1/0.50 max battery discharge * 1/12 volt battery bank = 196 AH @ 12 volt battery bank
So--While you should be able to run with a 200 AH @ 12 volt battery bank (2x 6 volt @ 200 AH golf cart batteries)--With a flooded cell battery, I would recommend a 480 AH @ 12 volt battery bank to support ~1,200 Watt starting load (AGM can use the 200 AH @ 12 volt battery bank).

Suggest 5% to 13% rate of charge for battery bank--And 10% or more for full time off grid (vs weekend/seasonal system usage). The solar array for such a battery bank would be:
• 480 AH * 14.5 volts charging * 1/0.77 panel+controller deratings * 0.05 rate of charge = 452 Watt array minimum
• 480 AH * 14.5 volts charging * 1/0.77 panel+controller deratings * 0.10 rate of charge = 903 Watt array nominal
• 480 AH * 14.5 volts charging * 1/0.77 panel+controller deratings * 0.13 rate of charge = 1,175 Watt array "cost effective" maximum
Note, the larger the battery bank, the larger the suggested minimum array.

Then there is sizing array based on energy usage and by season... You did not say if this was for backup power, full time off grid, inside or outside, generator backup, other power usages (LED lighting, cell phone charging, laptop computer, etc.)... A nominal system design would look like (assuming Missoula Montana):

### MissoulaAverage Solar Insolation figures

Measured in kWh/m2/day onto a solar panel set at a 43° angle from vertical:
(For best year-round performance)  Jan Feb Mar Apr May Jun 2.66 3.75 4.71 5.12 5.13 5.41 Jul Aug Sep Oct Nov Dec 6.11 5.90 5.20 3.93 2.86 2.37
Normally, toss the bottom three months (assume generator use for bad weather--And for a refrigerator out on the back porch, energy usage may fall in freezing weather), pick February as "break even month":
• 500 WH per day * 1/0.52 off grid system eff * 1/3.75 Hours of sun per Feb day = 256 Watt minimum array (Feb break even)
If, you expected 500 Watts per day, and little to no genset backup, then you should run daily power usage to 65-75% of designed power output (to allow for some bad weather), and if you pick December as break even month:
• 500 WH per day * 1/0.65 daily power usage * 1/0.52 off grid system eff * 1/2.37 Hours of sun per Feb day = 624 Watt array minimum (12 months per year)
If we go back to suggested minimum solar array for battery bank (based on starting surge current), it was ~903 Watt array for 10% rate of charge with a 1,200 Watt minimum AC inverter....

So--Without knowing much about where you are located, if you will use genset for winter/bad weather, etc... At this point, I would be suggesting a ~903 Watt minimum array (note, solar math is not that exact.... I am using 903 Watts so you can see where I am pulling the numbers from -- Anything within ~10% is pretty much "exact" in solar power estimate).

And possibly a larger AC inverter (1,200 Watts minimum)... It is possible that your 1,000 Watt Tripplite will work fine for you--I just do not know.

Also, with a 903 Watt array--You will have lots of extra power for much of the season...
• 903 Watt array * 0.52 off grid AC system eff * 3.75 hours of sun (9 months of the year) = 1,761 Watt*Hours per day
That is enough to keep a cabin well lite and the folks entertained (laptop, cell phone, LED TV) and probably a 12 volt RV water pump for plumbing (surface water, or use deep well pump + cistern + genset or a "solar friendly" deep well pump).

-Bill
The Tripp Lite SW1012 will start and run the Freezer/Fridge, I haven't moved it to cabin yet, but at home it takes 200W a day to run, so it should be the same or less at the cabin, this is an off grid system, mainly to power the Fridge/Freezer when I am not there, If batteries are low after a weekend or major electricity is needed I can fire up the gen set. I want to be able to just power the Freezer/ Fridge. When I am not there power usage should be less as no one is around to open it.
• Registered Users Posts: 21✭✭
I already have the Freezer/Fridge so buying a new one is out of the question.

• Registered Users Posts: 21✭✭
still looking for an mppt controller.
• Registered Users Posts: 21✭✭
BB. said:
For a standard fridge/freezer--The 1,000 Watt inverter may or may not reliably start the compressor--Typically, 1,200 to 1,500 Watt is recommended for reliable compressor operation.

And, we do not know how much energy the freezer will use as a refrigerator... Just to be relatively conservative, lets guess 500 WH per day. 2 days of storage, and 50% maximum discharge (longer battery life) on a 12 volt battery bank:
• 500 WH per day * 1/0.85 AC inverter eff * 2 days storage * 1/0.50 max battery discharge * 1/12 volt battery bank = 196 AH @ 12 volt battery bank
So--While you should be able to run with a 200 AH @ 12 volt battery bank (2x 6 volt @ 200 AH golf cart batteries)--With a flooded cell battery, I would recommend a 480 AH @ 12 volt battery bank to support ~1,200 Watt starting load (AGM can use the 200 AH @ 12 volt battery bank).

Suggest 5% to 13% rate of charge for battery bank--And 10% or more for full time off grid (vs weekend/seasonal system usage). The solar array for such a battery bank would be:
• 480 AH * 14.5 volts charging * 1/0.77 panel+controller deratings * 0.05 rate of charge = 452 Watt array minimum
• 480 AH * 14.5 volts charging * 1/0.77 panel+controller deratings * 0.10 rate of charge = 903 Watt array nominal
• 480 AH * 14.5 volts charging * 1/0.77 panel+controller deratings * 0.13 rate of charge = 1,175 Watt array "cost effective" maximum
Note, the larger the battery bank, the larger the suggested minimum array.

Then there is sizing array based on energy usage and by season... You did not say if this was for backup power, full time off grid, inside or outside, generator backup, other power usages (LED lighting, cell phone charging, laptop computer, etc.)... A nominal system design would look like (assuming Missoula Montana):

### MissoulaAverage Solar Insolation figures

Measured in kWh/m2/day onto a solar panel set at a 43° angle from vertical:
(For best year-round performance)  Jan Feb Mar Apr May Jun 2.66 3.75 4.71 5.12 5.13 5.41 Jul Aug Sep Oct Nov Dec 6.11 5.90 5.20 3.93 2.86 2.37
Normally, toss the bottom three months (assume generator use for bad weather--And for a refrigerator out on the back porch, energy usage may fall in freezing weather), pick February as "break even month":
• 500 WH per day * 1/0.52 off grid system eff * 1/3.75 Hours of sun per Feb day = 256 Watt minimum array (Feb break even)
If, you expected 500 Watts per day, and little to no genset backup, then you should run daily power usage to 65-75% of designed power output (to allow for some bad weather), and if you pick December as break even month:
• 500 WH per day * 1/0.65 daily power usage * 1/0.52 off grid system eff * 1/2.37 Hours of sun per Feb day = 624 Watt array minimum (12 months per year)
If we go back to suggested minimum solar array for battery bank (based on starting surge current), it was ~903 Watt array for 10% rate of charge with a 1,200 Watt minimum AC inverter....

So--Without knowing much about where you are located, if you will use genset for winter/bad weather, etc... At this point, I would be suggesting a ~903 Watt minimum array (note, solar math is not that exact.... I am using 903 Watts so you can see where I am pulling the numbers from -- Anything within ~10% is pretty much "exact" in solar power estimate).

And possibly a larger AC inverter (1,200 Watts minimum)... It is possible that your 1,000 Watt Tripplite will work fine for you--I just do not know.

Also, with a 903 Watt array--You will have lots of extra power for much of the season...
• 903 Watt array * 0.52 off grid AC system eff * 3.75 hours of sun (9 months of the year) = 1,761 Watt*Hours per day
That is enough to keep a cabin well lite and the folks entertained (laptop, cell phone, LED TV) and probably a 12 volt RV water pump for plumbing (surface water, or use deep well pump + cistern + genset or a "solar friendly" deep well pump).

-Bill
Thanks Bill! I have four 6 volt batteries, i went with cheep batteries because I figure I will ruin first set any way.
• Solar Expert Posts: 3,830✭✭✭✭
edited August 2016 #10
Without the board, you probably would. Golf cart batteries work pretty well really. Especially is you can keep them charged, cool, and using thick cable seems to help.

Thanks Bill! I have four 6 volt batteries, i went with cheep batteries because I figure I will ruin first set any way.

First Bank:16 180 watt Grape Solar with FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
What size array do you want? Specific panels? Long or short cable run from array to charge controller+battery shed?

Do you want simple or computer logging or even Ethernet?

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Registered Users Posts: 21✭✭
320 watt plan to add one more 160 this year
• Registered Users Posts: 21✭✭
20 feet from panels to batteries
• Registered Users Posts: 21✭✭
I currently have 2 160w panels no logging short wire runs batteries in entry way
• Solar Expert Posts: 3,830✭✭✭✭
Your batteries may be dead in a couple months if you don't have the panel power. Then you lose what you have in the freezer/fridge. December is coming.....short, cloudy days. Try to put the freezer/fridge in a cold area. I'd add that extra panel asap.
First Bank:16 180 watt Grape Solar with FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
What is the Vmp/Imp rating of the panel(s)?

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Registered Users Posts: 21✭✭
softdown said:
Your batteries may be dead in a couple months if you don't have the panel power. Then you lose what you have in the freezer/fridge. December is coming.....short, cloudy days. Try to put the freezer/fridge in a cold area. I'd add that extra panel asap.
everything is still in town collecting parts before the install, fridge running on grid
• Registered Users Posts: 21✭✭

BB. said:
What is the Vmp/Imp rating of the panel(s)?

-Bill
18.5V & 8.65A
Your choice is to run your panels in parallel for charging a 12 volt battery bank (use PWM or MPPT), or run two (or more) in series with an MPPT controller.

Say you want 3x panels in parallel at 26 amps for 20 feet with 1% to 3% voltage drop. Using a basic voltage drop calculator:

http://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=1.296&amp;voltage=18.5&phase=ac&noofconductor=1&distance=20&distanceunit=feet&amperes=26&x=62&y=16

6 awg:
Voltage drop: 0.41
Voltage drop percentage: 2.22%
Voltage at the end: 18.09

2 awg:
Voltage drop: 0.16
Voltage drop percentage: 0.86%
Voltage at the end: 18.34

You can see that is pretty heavy copper cabling... If you instead put 3x panels in series (2 is really recommended for MPPT--A bit less MPPT controller heating/losses):

http://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=13.17&voltage=55.5&phase=ac&noofconductor=1&distance=20&distanceunit=feet&amperes=8.65&x=50&y=11

16 awg:
Voltage drop: 1.39
Voltage drop percentage: 2.50%
Voltage at the end: 54.11

12 awg:
Voltage drop: 0.55
Voltage drop percentage: 0.99%
Voltage at the end: 54.95

So--An MPPT controller will allow you to use much less copper for your wiring run (probably 14 AWG or heavier wire recommended for mechanical strength).

A nice 30 amp MPPT charge controller (not cheap @ \$290):
https://www.solar-electric.com/midnite-solar-kid-mppt-solar-charge-controller.html

And a simple 30 amp PWM charge controller (\$90)
https://www.solar-electric.com/midnite-solar-brat-pwm-solar-charge-controller.html

Notice the besides saving on the costs of copper at higher array (and battery) voltages (higher voltage means lower current)--The charge controllers are typically rated for a maximum current... On a 12 volt battery bank, you are looking at a ~480 Watt maximum array with 3x panels (in series or in parallel) and a 30 amp controller. With a 24 volt battery bank, the same controllers will manage a 2x larger array (~960 Watts--Or a bit more for MPPT).

Doing a couple of paper designs to see what works best (price/performance/needs) for you. With PWM controllers, you are typically limited to "12 volt" (Vmp~18 volt) panels on a 12 volt battery bank. With MPPT you can use "Grid Tied" panels with Vmp~30 volts or higher on the 12 volt battery bank--"GT Panels" are around 1/2 the cost per Watt vs "12 volt" panels... Spend less on solar panels (and wiring) and spend more on MPPT charge controller(s)--You need to do a paper design to see what works best for you.

Typically--Less than 400 Watt systems work out fine with PWM controllers. And >800 Watt arrays, typically MPPT charge controllers end up being a better choice.

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Registered Users Posts: 21✭✭
Yes i plan to slowly expand the system so a 30A MPPT Controller is in the picture /