Need stand alone system for 12V solar fridge

[longbowelk]

I am new to solar and this forum. I am retired but find this forum very interesting. I have an off grid cabin that is a week end plus getaway. My contractor friend and I recently installed the EG4 12K btu off grid minisplit that runs on 3 solar panels. I will post this one later. The subject today is I also set up a 10.3 cu ft 12V solar Unique fridge. We ran it 4 days alternating a 1000W Jackery and a 65 series AGM truck battery with 850cca. The Jackery did better than the battery as it would run it around 23 hours. The battery averaged about 12 to 14 hours.
The fridge only uses 56 watts when compressor is on. When I got back home I tested the 2 100W solar panels in full sun and was getting 124 watts. My next test on my next trip us to add a 12 ft 12ga extension and see if the Jackery and panels can run it . This system us temporary as I want to have a permanent system with a small charge controller and possibly 1 panel.
I am looking for recommendations and tips. Thanks, Alan

 

[Rednecktek]

How simple or complicated do you want to get? From the sounds of it you could go as little as a 100ah LFP, a 40a MPPT and a set of 4x 100w panels and be good to go for a day. From there it's all about expansion. Want 3 days of backup? 3 batteries. Want to be able to charge it fully in winter? A couple more panels and a 60a MPPT. Want to have 120v power handy if you want it? A 12v AIO like the MPP 1012LV and a DIY 280 or 304ah battery in a small shed gets you 120v and 12v supply.

Just to throw some numbers at you to play with, the Jackery is about 1000wh of power and a 100ah LFP battery is 1280Wh. Rule of thumb is 4 hours of good sun a day so 1280Wh / 4 hours = 320w minimum solar panels, call it 400w for inefficiencies and overhead. If you go with a single panel you'll have to have a proper MPPT controller to utilize the higher voltage of a larger panel. Pro tip: If it has a USB port on it, it's a FAKE controller with a sticker saying MPPT and they'll laugh all the way to the bank.

The problem you were running into is that you couldn't refill the batteries as fast as you were draining them. 56w doesn't sound like much, but over 24 hours it adds up so you've got to be able to put 24 hours of power into the batteries in a 4 hour window.

Doing a DIY 304Ah battery will run you about $600 all in if you feel up to it. That's a lot of power in a small footprint and since most weekend cabins don't come with a 2 car garage, footprint is a factor.

 

[sunshine_eggo]

I have a 10.1 cu-ft AC fridge, and it uses 0.8kWh/day. The compressor burns 60W when running.

It sounds like your consumption is pretty similar.

300-400W in good PV conditions should cover you. More when crappy OK winter hits.

 

[longbowelk]

Thanks for info. I think I will eventually end up with 1 or 2 decent solar batteries and 3 panels. My original trial run was about what I was expecting after a couple days of real world experience. I knew we would run out of power by day 5 but we went ahead on morning of day 5 and shut fridge off so it could be thawed out when we left. On return we will have to cool cabin which will also cool the fridge before we can turn it on. So on a 5 day trip we really only running it 3 days. So although we presently under powered we will have more time to come up with a solid solution. I do value the input I have received here so a Thanks for that.