Why do we need an off grid solar fridge
There are many reasons that you might want to use a fridge while camping.
The first and foremost is to keep your food and drinks cold or frozen.
It is seen as an important part of our lives to be able to use refrigeration to keep our food fresh and last longer.
If we eat food that has been out of refrigeration too long it can cause health issues.
We may just want to keep the beer cold.
Or maybe we want to enjoy a bowl of ice cream
Whatever the reason for wanting a fridge, we need to know that we can run the fridge safely.
What do I need to make the fridge work?
There are only a few things that you will need to get everything working.
It boils down to 3 things:
1. The fridge input voltage and wattage.
2. A power source to match the fridge voltage with enough storage capacity.
3. Someway to recharge the battery.
Many off grid solar fridges will be either 12 v or 24 v or able to use either.
A power source will be required, this is usually in the form of a battery. You can check out the Off grid solar post I have previously made.
You will also need a way to recharge the battery, this is either a generator, your car engine, a solar panel or maybe a wind generator.
Since we are talking about an off grid solar let’s assume we are using a solar panel. The calculations will work the same.
How do I know if the fridge will run all night?
We need to look at the power consumption of the fridge.
You will need to locate the sticker that is normally near the power connector and check for a number that shows the number of Watts or the number of Amps, and a number showing the input voltage.
If it shows 4 W and a 12-volt input, for example, then we can assume that when the fridge compressor is running the current draw on the battery is 1 third of an Amp, when the compressor is not running it will still draw a small amount of current, but this will be negligible.
We then need to think about how often the fridge reaches the desired temperature and the compressor will turn off. Then how long it will take for the temperature inside to rise before the compressor will start again.
If we are opening the fridge often the cold air will be released, and the compressor will need to cool down the air inside again, this will use more power.
We also need to think about how many hours of darkness there will be before the solar panel will be able to start putting charge back into the battery.
My example
My
What I did
My first camping fridge had an input volage of 12 V.
The sticker on the side of the fridge showed it would draw 4 Amp at 12 V. This calculates to be 48 Watts.
The fridge had a duty cycle of 1 in 4. This means that if the door is not opened then for every 5 minutes the compress runs there will be 15 minutes of no compressor. Or for every hour the compressor will run for 15 minutes. If the fridge is in the sun all day the compressor will be on longer.
The capacity of the battery I had was fairly small, around 80AH
My solar panels had a rating of 120W.
Let’s assume there are 12 hours of daylight and 12 hours of darkness.
Let’s look at the worst case scenario. If the fridge is in the sun and the compressor needs to be running constantly to keep the fridge cold. We would be drawing 48W of power or 4 Amp at 12 Volts every hour. With an 80AH battery this will allow the fridge to run the battery completely flat in only 20 hours. Now to keep the battery healthy we do not want to run an AGM battery to less than 50% of the battery capacity. This means the battery will get to 50% in only 10 hours.
Now let’s look at what might happen if the fridge in the shade, and I do not open the door, allowing it to reach the desired temperature and the compressor turns off. The compressor will only be using 1/4 of that power each hour. Which equals 1 Amp every hour. Meaning we will actually get around 40 hours out of the 80AH battery using the fridge. This is a best case scenario, if we open the fridge more the power drawn will be higher. This reduces the total time the battery can keep the fridge going.
I also connected the 120W solar panel to the battery. Which means that for every hour of sunlight I am putting back into the system 120W, we then have to minus off the power drawn by the devices connected to the system. If the fridge is using around 48W every hour, I have 72 W every hour that can be used to replenish the power drawn from the fridge when the sun was not shining. If the sun does not shine for 12 hours the next day, then the fridge might stop during the night.
80AH battery. 40AH usable with 12V = 480W
8 hours of sunshine = (Solar panel W) x (hours of daylight) = 120 W * 8 H = 960 W
8 hours of fridge in the sun = 48 W * 8 = 384 W
Leaving 560 W which is more than the 480 W capacity of the battery
16 hours of power drawn overnight = 1 A * 12 v * 16 hours = 192 W used overnight.
This means that after using the 192 W overnight, I have used approximately 75% of the battery and the power drawn using the fridge during the day I can add more devices to the system as there is more capacity than what is being used. Or I could use a smaller battery. Or I could get less hours of sunlight and will still allow the system to last many days.
Additional information
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