We are trying out an Alpicool freezer-refrigerator for our Overlanding adventures. We run it from a 12V accessory outlet during the day, and at night we use a dedicated battery.
Why a freezer
We bought a portable freezer-refrigerator for two reasons. The first is our convenience, no more dealing with ice and water. The second is it allows us to increase the variety of meals we fix by using frozen ingredients.
The freezer has to be powered continuously. When Campbell is on the road, we power it from a 12V accessory outlet, and we need a way to power it at a campsite.
We like to prove additions to our kit in the field before we fully commit. In the future, we might add a LiFePO4 house-bank and solar.
So we decided to use an inexpensive battery to operate the freezer instead of adding temporary wiring to the starting battery. The experience will also help us design the house power when the time comes.
We don’t usually stay for more than one night at a campsite before driving to a new location. So the battery needs to run the fridge overnight. We will charge it while we are driving.
When we stay in lodging, we will take the fridge into our room and power it from a 120V outlet.
These are the temperatures for our measurements:
- Ambient Temperature: 72 degrees Fahrenheit (22c)
- Freezer Setting: 10 degrees Fahrenheit (-16c)
- Hysteresis: 4 degrees Fahrenheit (2c)
We found that it alone would not comfortably run the freezer overnight. So we bought a second. Here are the specifications for the EXP12200.
Twelve or Twenty-Four Volts
With two batteries, we can run the freezer on either 12v or 24v. We compared the power usage, and the Alpicool has the same efficiency at both voltages.
This table shows the current and nominal power of the twelve-volt and twenty-four-volt banks fully charged:
|12-volt||3.4 amps||41 watts|
|24-volt||1.7 amps||41 watts|
We use the batteries wired in series for a twenty-four-volt bank. The lower current reduces the voltage drop in the wiring when compared to twelve volts. It is also better at keeping the cells balanced.
A measure of the discharge rate of a battery is c-rate. It is the proportion of load-current in amps to the amp-hour capacity rating of the battery. The capacity of the series-wired twenty-four-volt bank is 20ah, so the c-rate is the load-current divided by twenty. A lead-acid battery bank can provide more energy at a lower discharge rate, effectively increasing its capacity.
Energy-Saving vs. Fast-Cooling
The Alpicool has two power modes, energy-saving (ECO) and fast-cooling (MAX). We typically use the ECO setting when running on batteries. In both modes, the current begins at 1.7 amps then stabilizes. A current of 1.7 amps is a c-rate of 0.9c.
This table shows the current of each power mode for the fully charged twenty-four-volt bank:
The Alpicool has three battery-protection modes High, Medium, and Low. This table shows the run time and no-load voltage for each battery-protection mode using the twenty-four-volt bank running in ECO mode:
The EXP12200 is rated for 400-500 charge-cycles when the depth-of-discharge (DOD) is 50%. The cycle rating is 260 for a DOD of 100%.
We don’t routinely exceed a 50% DOD, but we care more about our food remaining frozen than the battery life. When the batteries reach the end of their life, they will only have 60% of their capacity. For those reasons, we use a medium setting.
We charge the battery from Campbell’s 120v outlet while we are driving. At that time, the Alpicool is running from a 12v accessory outlet. It recharges from 100% DOD in 8.5 hours.
We use a seven-stage Foxsur charger to charge the batteries. It can supply up to three amps to charge a 24-volt bank. We like that it can also charge 12 volt, LiFePO4, and Lithium batteries.
We will report back after using the freezer for a while and let you know how it is working for us. So please check in occasionally to follow our journey.