Powering a small chest freezer in my garage.

[Aldog]

I'm fairly new to solar power. My experience to date is: I have a small boat with a marine 12v/120 ac refer/freezer. I used a Renogy 100watt starter kit to power the unit.It came with the 100w panel, a waterproof controller, and 30 feet of cable. I have a duel battery system and I can isolate the house battery from the starting battery. The system has worked perfectly for 3 seasons, and has me interested in doing something like that for my small chest freezer in my garage.
I have started collecting some of the stuff that I'll need. I have 4 540watt commercial panels that I could mount on the garage roof. I also have a 12v to 120v inverter that was used to power a small refer unit on my pickup truck and 2 new 12 volt car batteries. That's it so far. I was planning to buy the Renogy 600a controller and enough cable to tie everything with connectors, fuses, and a shutoff.
I want the freezer to be off-grid for emergency and I would like to power it 24/7 365. Am I headed in the right direction ? I'm open for suggestions. Thanks, Al

 

[sunshine_eggo]

Maybe

What is the energy consumption on your freezer? Many models have the yellow sticker that shows $ or kWh/used per year.

 

[Supervstech]

I'm fairly new to solar power. My experience to date is: I have a small boat with a marine 12v/120 ac refer/freezer. I used a Renogy 100watt starter kit to power the unit.It came with the 100w panel, a waterproof controller, and 30 feet of cable. I have a duel battery system and I can isolate the house battery from the starting battery. The system has worked perfectly for 3 seasons, and has me interested in doing something like that for my small chest freezer in my garage.
I have started collecting some of the stuff that I'll need. I have 4 540watt commercial panels that I could mount on the garage roof. I also have a 12v to 120v inverter that was used to power a small refer unit on my pickup truck and 2 new 12 volt car batteries. That's it so far. I was planning to buy the Renogy 600a controller and enough cable to tie everything with connectors, fuses, and a shutoff.
I want the freezer to be off-grid for emergency and I would like to power it 24/7 365. Am I headed in the right direction ? I'm open for suggestions. Thanks, Al

Im not sure what you actually have...
I have never heard of a 600A controller.

 

[sunshine_eggo]

Im not sure what you actually have...
I have never heard of a 600A controller.

MOAR POWA!!!!

 

[Supervstech]

A chest freezer will use about 2x what a small 120v refrigerator.
In a garage, temps tend to soar in summer, so that will hurt your runtime as well.

Car batteries are REALLY bad for solar, they only last as long as they are held to full charge...

You are better getting golf cart batts, or lithium, even deep cycle would be better than car batts, but not much better.

 

[Supervstech]

2160W into a 12V bank will need about 300A controller...
And a HONKING LARGE battery bank.

 

[sunshine_eggo]

Example:

Small? 6.9cu-ft:

Vissani 6.9 cu. ft. Manual Defrost Chest Freezer with LED Light Type in White Garage Ready DCM7QRWW - The Home Depot

Bring freshness to your life with the garage ready VISSANI 6.9 cu. ft. chest freezer. With the freezer's interior LED light, you can easily find your frozen foods. This product is tested to perform indoors

www.homedepot.com

https://images.thdstatic.com/catalog/pdfImages/ca/caeb3918-1770-4cf3-97df-bcc04d1122e9.pdf

249kWh/year.

The new standard that generates those values is based on sitting unopened in 90°F ambient temps. Personally, I would double it since you're in a garage.

500kWh/year / 365 days/year = 1.4kWh/day

You'll need 1.4kWh of usable battery capacity per day of backup.
You'll need about 500W of solar, optimally tilted with unshaded exposure from sunrise to sunset.

Scale the system according to your chest freezer consumption.

 

[Mattb4]

..
I have started collecting some of the stuff that I'll need. I have 4 540watt commercial panels that I could mount on the garage roof. I also have a 12v to 120v inverter that was used to power a small refer unit on my pickup truck and 2 new 12 volt car batteries. That's it so far. ...
I want the freezer to be off-grid for emergency and I would like to power it 24/7 365. Am I headed in the right direction ? I'm open for suggestions. Thanks, Al

You have the solar but you need a better SCC, Battery, inverter setup. I would suggest a AIO (All In One) in either 24vDC or 48vDC battery. Likely you will want a high PV voltage model for your 540W commercial panels.

You likely can expect 1.5 to 2kWh for the freezer each day. Add in another 1.5kWh for overhead operation of your components. Your panels at 2160W could supply between 4200Wh upwards of 9kWh each day. Your battery should supply at least the 3kWh for a days operation without PV. For example if you get a 50ah 48vDC LiFePO4 battery you will have ~2.5kWh, lead acid would double the need to be 100ah for the same amount.

 

[Suijkerbuijk]

Example:

Small? 6.9cu-ft:

Vissani 6.9 cu. ft. Manual Defrost Chest Freezer with LED Light Type in White Garage Ready DCM7QRWW - The Home Depot

Bring freshness to your life with the garage ready VISSANI 6.9 cu. ft. chest freezer. With the freezer's interior LED light, you can easily find your frozen foods. This product is tested to perform indoors

www.homedepot.com

https://images.thdstatic.com/catalog/pdfImages/ca/caeb3918-1770-4cf3-97df-bcc04d1122e9.pdf

249kWh/year.

The new standard that generates those values is based on sitting unopened in 90°F ambient temps. Personally, I would double it since you're in a garage.

500kWh/year / 365 days/year = 1.4kWh/day

You'll need 1.4kWh of usable battery capacity per day of backup.
You'll need about 500W of solar, optimally tilted with unshaded exposure from sunrise to sunset.

Scale the system according to your chest freezer consumption.

That somting correct .
I use a freezer.
Its a 65 watts model +10% inverter lost is about 71.5 watt. ( Compressor pump model)
I need to charge about 1.5 kwh for this freezer to run in the summer and charge the battery.
This on 24 hours time use
In the winter you need les the freezer do not jump on that fast .
Other point solarpanels do nothing in the winter.
In the summer you can even run it with 2x100 watt panels (i have done that)

 

[sunshine_eggo]

That somting correct .
I use a freezer.
Its a 65 watts model +10% inverter lost is about 71.5 watt. ( Compressor pump model)
I need to charge about 1.5 kwh for this freezer to run in the summer and charge the battery.
This on 24 hours time use
In the winter you need les the freezer do not jump on that fast .
Other point solarpanels do nothing in the winter.
In the summer you can even run it with 2x100 watt panels (i have done that)

His climate is incredibly hot. His summer garage temperatures can exceed 50°C.

You're right about winter, fridge only comes on 0.5 to 3 times per day in current cold temps:

 

[Suijkerbuijk]

His climate is incredibly hot. His summer garage temperatures can exceed 50°C.

You're right about winter, fridge only comes on 0.5 to 3 times per day in current cold temps:

View attachment 254824

I know .
In my boat the temperature is about 43 celcius.
And the freezer is on that space.
If i'm away the temperature go even up easy to 50 celcius.
So i know that freeze will run for its money.

 

[Aldog]

Im not sure what you actually have...
I have never heard of a 600A controller.

Sorry, I think what I meant was a 100amp controller. Thanks

 

[Aldog]

Wow! Thanks for all the help! I have not purchased anything yet and you have given me a lot to think about. I'm kind of a prepper and refrigeration is one of the few things I don't have covered. My 12 volt portable refrigerator / freezer does a great job running on a 12 v deep cycle battery, 100w panel and 10 amp controller. I can see I need to bump it up a lot. Thanks again, guys.

 

[sunshine_eggo]

Wow! Thanks for all the help! I have not purchased anything yet and you have given me a lot to think about. I'm kind of a prepper and refrigeration is one of the few things I don't have covered. My 12 volt portable refrigerator / freezer does a great job running on a 12 v deep cycle battery, 100w panel and 10 amp controller. I can see I need to bump it up a lot. Thanks again, guys.

If you design to the energy requirements, you won't be sad. Process (not asking you the questions. They're for you to answer yourself):

1) How many kWh/day does the freezer need (2X the yellow sticker value)?
2) Multiply that number by the number of days you want battery backup in kWh.
3) Divide the kWh from #1 by 4 hr to get PV power and round up a bit.
4) Pick your desired battery voltage and divide the PV power by 14.4, 28.8 or 57.6 for 12V, 24V or 48V battery voltage as you select to determine how much MPPT current you'll need.
5) pick your desired battery chemistry and adjust as needed via a nuanced set of rules we can help you with.

Now you select components.

Component selection tips:

• Watch out for cheap AiO (all in one - the ones that have everything including MPPT in one case). They can burn more power than the freezer itself simply being turned on. It's always a good idea to go back to your daily kWh value, adjust it by the inverter consumption, and reconsider your calculations.
• Consider getting an inverter/charger rather than just an inverter. That way, you can use grid to charge batteries if you happen to get a string of bad days.
• Your freezer compressor likely has a surge current 5-6X higher than the run current. You either need to get an inverter with suitable surge, or a weak-surge inverter whose continuous rating is higher than the surge current. In any case, you're likely looking at something in the 1000W range.
• The "nuanced" bit about batteries depends on LFP or lead acid. LFP is very flexible, but lead acid typically require specific charging requirements where it's easy to get too much or too little charge current, especially if you're looking at multiple days of backup.

Note that the above is a bit conservative, so you will likely over-spend 10-20% (pure swag), but it should be a very robust system without being overkill... even though overkill is underrated.

It should also provide some surplus, particularly in the non-winter months for things like charging tools and possibly even heavier utilization.

 

[HarryN]

Most home refrigerators in the US have a sticker on the inside with the estimated power use per year.

On mine and the ones that I looked at in the stores, a typical number is 1 - 2 kW - hrs per day ( average ) , with 2 being more common.

Part of this power goes to auto defrost.

So let's use 2 kW-hr / day
_______-

A few inverters have lower standby power, but a common number is 30 - 40 watts, even with no load, so

( 40 watts ) x ( 24 hrs / day ) ~ 1 kW-hr

So that is on top of the refrigerator load.

The inverter that I am using appears to be running a 12 watt standby but that is less than the official factory data sheet, so

( 12 watts ) x ( 24 hrs / day ) ~ 300 watt-hrs.

It is an expensive inverter though, so most people would not buy it.

_____________

The refrigerator in my garage starts to act up temperature control wise when it is hot. So what turned out to help a lot was to add a fan that blows air through the coil area and I just keep it on all of the time. It gets to 45 C here routinely in the summer.

I was desperate for a solution, as we were having food thaw in the freezer, and eggs / other stuff freeze in the refrigerator side. It was also running literally 24 x 7 and I was concerned that it would burn out. So for now it is just a 20 inch box fan from target and not optimized. Uses something like 50 watts. So:

( 50 watts ) x ( 24 hrs / day ) ~ 1 kW-hr per day

____________________

So right there is ~ 4 kW-hr / day for just the garage refrigerator, but it is critical for us.

__________________

We have power outages here, mostly during fire season, so I have that and a few other items like an extra microwave and a light in the garage on a DIY back up, made from stuff that I already owned.

- 4 x Lifelne AGM 100-amp-hr batteries
- 1 kW inverter
- Bogart solar controller
- Fuse block
- 120 vac charger

The Bogart solar charge controller, and frankly most solar charge controllers, have a much lower standby power draw than the renogy ones, so I suggest buying something else - literally anything else.

Under normal use, it just acts like a UPS for those items.

When power is out, I put some solar panels on the driveway if the outage is going to be very long and run it from that.

_______________

For solar generation budgeting purposes - in this area, I use:

( solar panel rated watts ) x ( 50%) x ( 6 hrs / day ) = what I can usually count on - but this depends a lot on the season and how much smoke is in the air. But as an example

( 800 watts of solar panels that I have in the garage ) x ( 50% ) x ( 6 hrs / day ) ~ 2400 watt-hrs generated vs the needed 4000 watt-hrs to power the garage "work bench power system"

So it helps, but I still need to turn things off to make it work.

 

[Chispas]

2 new 12 volt car batteries.

Welcome aboard, you're in the right place. Im a fellow beginner & have learnt that we numbers to give the right suggestions . So what do the car batteries have on the sticker in regard to A or AH ?

 

[T-Rex]

Make sure you plan very well before you buy anything.
I decided I didn't want 48v due to the cost of expanding the battery bank. Well it's a good thing I can series 24v batteries to make 48, because I'm looking at needing more capacity for what I want to run.... I will still have to replace the inverter.

 

[HarryN]

Make sure you plan very well before you buy anything.
I decided I didn't want 48v due to the cost of expanding the battery bank. Well it's a good thing I can series 24v batteries to make 48, because I'm looking at needing more capacity for what I want to run.... I will still have to replace the inverter.

You could also double the size of the battery bank by running them in parallel.

 

[HarryN]

@RV8R has posted extensively on this subject with actual data from using a 600 watt array with a Victron inverter in an off grid cabin.

Maybe he can provide a link to his posts on the subject.

 

[T-Rex]

You could also double the size of the battery bank by running them in parallel.

Thinking of how I can re-arrange but keep bumping against the "4p" limit...
Enough hijack, the point is, plan, plan and re-plan.....

 

[RV8R]

@RV8R has posted extensively on this subject with actual data from using a 600 watt array with a Victron inverter in an off grid cabin.

Maybe he can provide a link to his posts on the subject.

That thread & fridge energy use is here;

Thread 'Tiny Cabin - What To Do'
https://diysolarforum.com/threads/tiny-cabin-what-to-do.85978/

 

[MattMan119]

I have three chest freezers and they all putt 1.2kwh a day in regular cycles, but I have 20a charge controller with 24v .. and 100ah 24v drops about 30% each night, with 2x370w panels it charges almost everyday by1pm and repeats each day…

I drained it down one night to check recovery ..