Portable 12V Refrigerator

The Alpicool CF55 is more like a cooler than a fridge, but it does run on 12v with a provided car cigarette-lighter adapter or via 120v with a separate adapter and power block for that. It has a freezer section and a small fridge section that is big enough to hold about 20 standard-sized soda cans. The freezer section is big enough to hold a bit more than twice that.

While it is not a great replacement for a small fridge you’d find in a typical RV, it is a great option while traveling or for our tiny shed-cabin at Rally Creek. It holds about as much as a medium-sized cooler and the built-in 12v compressor works well for keeping things cold without the need to go out and get ice. A good solution for long weekends at the cabin.

Why A 12V “Plug In” Cooler?

While there are plenty of mini-fridge options out there that are cheaper, bigger, or both – the main reason for going with this model is that is does run on 12 volts. Typically a 12v fridge is designed to be put in a 4-wheeler or other off-road vehicle so they are built to be a bit more rugged than usual. They can also be extremely expensive because of this. Some of the units reviewed were over $1,000 for something maybe twice, usually less than twice, the size. For us, this is a good starting compromise to see how things work.

Why 12v if we are just leaving in the cabin and don’t need the rugged “in motion off-road-ready” features? Because we want something that runs efficiently on a 12v (or 24v) solar array. With any power system, converting from alternating current (AC) to direct current (DC) systems introduces a notable inefficiency. Currently the best inverters that convert solar-based DC power to AC power run at best around 88% efficiency. Many inverters run at less. By skipping the DC=>AC conversion we save at least 12% on energy consumption and in real-world scenarios more likely 15-20%. Every increase in efficiency of the system reduces the size of the solar panels needed (less wattage) , smaller battery storage, and smaller charge controllers. This is a case where you can directly see the increased cost of being inefficient.

Powering A Fridge With The Sun

Now that the Alpicool CF55 has proven itself capable of keeping drinks and food cool for an entire 3-day stay at the cabin, it is time to move it off the 120V 15A circuit we have at the cabin as a backup and continue our off-grid movement. Let’s look into the electrical details of this unit.

Fridge Details

The Alpicool CF44 reports average annual consumption of 190 kWh. That doesn’t tell us a lot about the unit itself and what the peak and nominal load will be. It also is shown to consume 60W as the rated power input. AC is 1.2A – 0.5A and DC is 5.0A / 2.5A. From that we can infer:

Consumption: 60W
AC: 110V @ 1.2A / 220V @ 0.5A
DC: 12V @5.0A / 24V @ 2.5A

Solar Power Generation/Storage

Our “baby solar panel experiment” setup has the following characteristics…

Battery

21AH in a 12v gel battery

Panel

100W panel , real-world output max 4.2A @ 12v, guesstimate 2.5A average @ 12v
Operating Voltage: 18V
Operating Current: 5.56A
Open Circuit Voltage: 22.5V
Short Circuit Current: 5.84A
Connection: MC4 standard solar power connector
View the details on Expert Power’s 100W Monocrystalline Solar Panel

Controller

Solar Input: 50V max, 20A
Battery Output: 12/24v
Load: 10A Max
Connection: Screw terminal for spade style connector, up to #14AWG
IP30 Rated
View the details on Expert Power’s 10A PWM Solar Charge Controller

Calculations

For this system running at a nominal 5A @ 12V, we will want to add a 100AH battery storage. This will provide up to 20 hours of support for the cooler, however there will be some system losses to heat as well as the composting toilet fan (0.07A) running of the same system. For this system we will want to keep the 12v rating, so we will wire the batteries in parallel to add the amp-hours (AH) of storage.

The solar panel at 2.5A (estimate) – 4.2A (max) will not keep up with the charge, so we will need to add more solar input to this system. Another 100W panel should do the trick, but maybe a 200W. Connected in parallel panels will remain at 12v output but push up the current. In series, panels will multiply the voltage. For this application we want to stay in parallel. DO NOT mix-and-match significantly different operating voltage or operating current in panels. For details read this article at Solar Panels Venue.

Solar Fridge Kit Options

100Ah 12v Battery

Renogy	Deep Cycle AGM	30A Max Charge	$224 at Home Depot
Expert Power	LiFePO4 – EP12100	50A Max, 12.8V Nominal, 14.4V Charging F12/M8 terminal 2Y Warranty	$330 at Expert Power
Expert Power	EXP100 Deep Cycle Gel	M8 terminal 1Y Warranty	$219 at Expert Power
Renogy	Deep Cycle AGM	3A Max 2Y Warranty 13.1″ x 6.9″ x 8.6″ 63.9 lbs	$190 at Amazon

Battery Cables

WindyNation	12″ 2 AWG	5/16″ Lugs (M8), stranded copper	$15 at Amazon
Battery Cables USA	12″ 2AWG	M8 Ends (5/16″) (2) 12″ cables, 1 red, 1 black	$19 at Battery Cables USA

Solar Panel : 100W 12V

Expert Power	100W Monocrystalline Solar Panel	Max/Rated: 18V @ 5.56A Open: 22.5V Short: 5.84A 40.16 x 20.08 x 1.38 in.	$105 at Expert Power
Renogy	RNG-100D-SS , 100W Mono Panel	Opt. 20.4V @ 4.91A Open: 24.3V Short: 4.21A	$83 at Amazon

MC4 Combiner

Expert Power	3-Way MC4, Connector Only	For 10-14 AWG, Up to 60A, 1000V DC	$12 at Expert Power
Export Power	Y Branch MC4 Connector	For 10-14 AWG, Up to 30A, 1000V DC	$10 at Expert Power