Rockpals’ First Car Freezer

Those who have known me know that I really like the Rockpals 500W battery power station for its compact size, but ultimately gave it away after falling in love with the Goal Zero Yeti 500x. It was no surprise then when one of my former coworkers bought the company’s car refrigerator/freezer last month, the 26qt Rockpals RP-25L, and asked for my opinion of it. At first glance, I really liked the look: solid black with accents of bright orange in a compact size. I told him that it probably was good based on my past tests with the solid battery power station.

As it turns out, the car freezer is Rockpals’ first one ever. Did it live up to my expectations? How did it compare to my Foho 54qt car freezer? I asked him if I could borrow it for a week for an evaluation.

Camping /Rockpals

What’s Good? What’s Bad?

Pros

• Tough-looking exterior with deep blacks and orange corner accents
• Excellent price
• Very compact (25.4″ x 17″ x 15.5″) and lightweight at 24.3 lbs
  • Should fit fine in every type of car
• Two sections: Freezer and small chiller
  • Temperatures are NOT independently controlled for each compartment
• Fast freezing
  • After 30 minutes, freezer section went from 81F to 42F, and the chiller was at 61F
  • After 50 minutes, freezer was 11F, and chiller 43F
  • Note: Refrigerant R134a is used
    • According to a thermal engineering website, R134a is a “non-flammable gas used primarily as a ‘high-temperature’ refrigerant for U.S. refrigeration and [car ACs]… [It] is non-toxic, non-flammable and non-corrosive.”
• Adjustable temperature: -4F to 50F (-20C to 10C)
  • Allows use as either a fridge OR freezer (with a fridge section — Warning: COULD freeze items in there overnight if the temperature is set too cold)
• Two (2) Energy modes: “HH” (High) and Eco
  • HH is useful when surrounding temperature is 86F+ (30C). Runs compressor at a higher speed
  • Eco mode, although using less energy, can ruin the compressor in the long run
  • “Power” LED: HH = Red. Eco = Green
• Temperature was roughly consistent during 4 days of continuous use. It was set at -4F, and spot checking throughout the day resulted in:
  • Freezer: Between -5F and 3F (in HH mode)
  • Chiller: Around 20F more than the freezer section. Eventually, anything left in the chiller froze too
  • Temperatures will fluctuate slightly more in Eco mode
  • Understanding how a standard refrigerator works will educate you how this car freezer similarly operates. See the TIPS section for more details
• Auto resume: When power supply is cut off and later restored, appliance continues operation

• Two (2) Power options
  • 12V or 24V car adapter (draws about 40W or 3.3A on 12V)
  • 100-240V AC wall plug, outputting 14.5V at 6.0A (or about 87W)
  • Cables for both included
• Low energy usage. (See TIPS section for calculating how long the car freezer could be used for on a battery power station)
  • Rockpals only uses power to reach or maintain set temperature (“Set” LED = Green). Once there, it goes idle (“Set” LED = Red)
    • The colder the set temperature, the more energy will be used
  • 52W with AC port of the Goal Zero Yeti 500X (8W of that is used by Yeti’s inverter)
    • Manual states up to 40W draw
  • 38W with 12V DC car port on the Goal Zero
  • 1W – 2W on idle (Red “Set” LED)
• Three (3) levels of Battery Protection to help prevent the car battery from running down
• Top opens sideways
• Product claims less than 45db of noise, but compared to the Foho BCD52, it has a noticeably louder hum
• Built-in LED over chiller section to help see in the dark
• Usable during off-roading
  • Works at up to 30 degree angle tilt
  • Anti-shake design keeps compressor protected
• Sturdy carry handles on both ends
  • Can secure Rockpals to car with straps, making it ideal for off-roading
• Can be used while the car is turned off, if its car port has a bypass to work directly off the battery
  • Many SUVs, trucks, and minivans today have such output at the back. Refer to the car’s owner manual

Cons

• There appears to be a CRITICAL bug where the compressor would not start. See ‘”Fahrenheit” Power-On Bug’ section below for details and workaround
  • Until this bug is fixed, keep the temperature unit display at Celsius
• May cause some annoyances when complete silence or darkness is needed
  • Fan or compressor is more noisy than I’d like
    • My current favorites, the Foho BCD-52 (55 qt) and Foho BCD-32 (34 qt), are far more quiet
  • LCD is VERY bright blue and cannot be dimmed
  • Buttons on the controller make very loud “Ding” sounds
• Like other car freezers in this price range, requires manual defrosting
  • To defrost and remove excess ice, power off the unit and wipe dry, then power back on
    • Do not allow a large amount of frost to build up on the inside of the walls as that will make cooling less efficient
  • I was not immediately able to find any portable car freezers that have an automatic, self-defrost cycle that “cleans” the freezer from accumulating too much frost
• No drain hole at the bottom to let excess or spilled liquid out
  • You will have to use a towel to pick up leftover liquid, especially after defrosting
• Chiller compartment may be too small for some
  • A small water bottle cannot stand upright. Cans will need to be on their sides
• Top opens sideways. Some may prefer a front open
  • Door latch does not give a satisfying, solid closure feel
  • Less vertical clearance is needed to fully open a side-mounted lid
• Product shipped to display temperature in Celsius
  • No obvious way to change Celsius to Fahrenheit
  • Rockpals was initially and understandably hesitant to show how to enter programming mode, citing that incorrect settings could damage the freezer
    • My friend and I figured out on our own how to enter programming mode and switch to Fahrenheit. See TIPS section on how to change
    • When asked, support would not provide information on what the various programming options were
• AC plug is only two-pronged, and as such, cannot be grounded
• No protective carry bag included
• No removable wire basket to easily load/unload content from freezer section
• No overload protection with a replaceable fuse
• Not waterproof. Keep it out of the rain
• No built-in cup holder on the lid
• Cannot be directly powered by Solar panels via MC4 or Anderson interfaces to make it a solar-powered freezer
  • GoSun has a cooler with a built-in solar panel
• English instruction manual is very skimpy on details
  • Japanese version appears to be more detailed and has additional graphics, but I cannot read it

Tips

• When you receive your car freezer, do NOT plug it in until it has stood upright for at least 10 hours to allow the refrigerant to settle
• Internal temperature is displayed on the LCD at power-on and updates periodically
• Power off/on by holding the “POWER” button for a few seconds
• To change temperature unit of display from “Celsius” to “Fahrenheit”, you will have to enter programming mode. See “Programming” section for more details
• There is no built-in battery
  • Requires a power station, 12V/24V DC/car port, 120V/220V AC, or solar panel(s) capable of providing at least 60W of sustained power

Settings

“Eco” Mode

“Set” button only cycles between Compressor Power and Battery Voltage Protection levels. It does not allow you to change display unit between Celsius and Fahrenheit like with the Foho BCD52.

Compressor Power: Eco or HH (Max). Default: HH

• “Eco” uses less power (runs compressor at lower speed) than “HH” (Max) to minimize draw on any connected battery, but can ruin the compressor in the long run
• “HH” (Max) runs compressor at full power
• “Power” LED: HH = Red. Eco = Green
• “Set” LED: Compressor running = Green. Idle = Red

Battery Voltage Protection: Low, Neutral (Medium), or High

• The car freezer will operate until the battery reaches a specific voltage level. Not setting the appropriate level could potentially leave you stranded with a car that will not start
  • Compressor stops when 12V battery reaches 10.3V (Low), 10.8V (Medium), 11.3V (High)
  • Resumes at 11.1V (Low), 11.8V (Medium), 12.6V (High)
• When connected to a battery power station: Use Medium or Low
• When connected to a car: Use High or Medium

Programming

To enter programming mode: Hold the “Down”, “Up”, and “Set” buttons at the same time until you see “E1”. Cycle through the options by pushing “Set”, and change values up or down with the respective “Up” or “Down” buttons. To accept the setting, leave the screen blinking until it stops after a few seconds.

Here are the various options that can be programmed. They should not be modified as they could cause your freezer to fail or be damaged.

PROGRAM AT YOUR OWN RISK!
Note that Rockpals support would NOT provide information on what the options are for, and so I am drawing on my experience gained with the Foho BCD52 car freezer. Without official confirmation by the manufacturer, make changes at YOUR OWN RISK.

• E1: Most likely, lowest temperature that freezer can be set to cool down to. -40C/-40F to Target temp. Default: -20C (-4F)
  • Caution: setting the value too low may damage the compressor
• E2: Most likely, highest temperature that freezer is allowed to reach. Target temp to 40C/104F. Default: 10C (50F)
• E3* and/or E4*: Unknown. Most likely, difference from target temperature before powering up compressor again. 0C/0F to 10C/18F. Default: 2C (3.6F)
  • Compressor should stop at target temperature (ie. 4C), and start again when internal temperature is E3 and/or E4’s value above it (ie. 4C + 2C = 6C)
• E5: Most likely, time delay protection. 0-10 mins. Default: 3 min
  • To protect the compressor, it will wait that amount of time after being idle/powered off before turning on again
• F1*: Unknown. Do not modify. Most likely, temperature compensation. -10C/-18F to 10C/18F. Default: 1C (1.8F)
  • If indeed temperature compensation:
    • Setting most likely applies for when temp is set to above -6C/21.2F
    • Displayed temperature = Detected temperature + Temperature compensation
      • Used to match Displayed temperature to what is actually Detected inside the unit
• F2*: Unknown. Do not modify. Most likely, temperature compensation. -10C/-18F to 10C/18F. Default: 2C (3.6F)
  • If indeed temperature compensation, setting most likely applies for when temp is set to between -12C/10.4F and -6C/21.2F
• F3*: Unknown. Do not modify. Most likely, temperature compensation. -10C/-18F to 10C/18F. Default: 3C (5.4F)
  • If indeed temperature compensation, setting most likely applies for when temp is set to below -12C/10.4F
• F or C: Temperature display unit. Fahrenheit or Celsius. Default: C (Celsius)
  • [Update 7/19/2020 – WARNING: I’ve been contacted by a few individuals that changing theirs to Fahrenheit caused unexpected cooling behavior. One of my friends even bricked hers (compressor would no longer turn on at all). Do NOT change until Rockpals has acknowledged the issue and found a fix]

* Each difference of 1C is 1.8F

Temperature Compensation

If you find the temperature displayed on the control panel is different than what is actually inside, the discrepancy can result in content overcooling or being too warm. For instance, if you meant to keep fruit cool at a set 40F, but the true temp inside is 32F, you will unintentionally have FROZEN fruit. Or, if you wanted to keep meats frozen at 29F, but the true temp inside is 36F, you may find the content having melted.

The above Program settings were EDUCATED GUESSES based on my experience with the Foho BCD-52 and Domende HC-50 car freezers. Rockpals Support would neither provide nor confirm the Program settings. With that in mind, ASSUMING that the configurations mentioned for E3, E4, and F1 – F3 are correct, here is how Temperature Compensation is used:

The displayed temperature should be roughly the same (by about 3.6F by default) as the actual one inside because the compressor will ONLY stop cooling when the display (not the storage’s true temp) matches the set degrees.

If you find the temperature displayed on the control panel is different than what is actually inside, the discrepancy can result in content overcooling or being too warm.

To correct the discrepancy between the set/displayed temperature and what the internal storage really is, place two, reliable thermometers inside and perform tests with temps set to 0C, -9C, and -20C (one for each of the F1 – F3 ranges). I found the calibration easier to start with the warmer values first. If, for example, the display is 8C, 4C, and 1C higher (for each range) than what is inside, set the temperature compensations to: F1 = -8C, F2 = -4C, and F3 = -1C.

Runtime with Battery Power Stations

• To calculate how long the car freezer could be used for with a battery power station depends on the battery’s capacity (Wh) and how much power (W) the Rockpals draws
• Examples are with a Jackery Explorer 1000 (1002 Wh). Halve the time when used with a Rockpals 500W or Goal Zero Yeti 500x (500Wh)
  • Plugged into AC port: 1002 Wh x 0.85 / Device Wattage
    • As short as 16.3 hours (1002 Wh x 0.85 / 52W). Longer when idle
      • Informal testing found an estimated use of 500-670 Wh/day as a fridge. It was idle much of the time
    • About 10-15% of power is lost during conversion from DC (battery) to AC, which is normal for all power stations
  • Plugged into DC port: 1002 Wh / Device Wattage
    • As short as 25 hours (1002 Wh / 40W). Longer when idle

Rockpals only uses power to reach or maintain the set temperature. Once there, it goes idle to minimize power draw. As such, the Rockpals could last a lot longer than the times listed above

Cooling Efficiency

Features /Rockpals

• Rockpals only uses power to reach or maintain the set temperature (“Set” LED = Green). Once there, it goes idle (“Set” LED = Red)
  • Time can be shorter or much longer, depending on how often the Rockpals’ compressor needs to be activated to reach or maintain target temperature
• The colder the set temperature and/or the warmer the ambient (surrounding) heat, the more energy will be used
  • Keep in a cool location and out of direct sunlight for best efficiency
  • Consider putting the Rockpals in an insulated bag for better cooling
• Ensure adequate air flow (4″+) on all sides of the Rockpals, especially where the fan is at
• The more frozen/cold items are inside, the longer they can stay cool/frozen. Avoid opening the lid too often or for too long

Maintenance

• Ensure lid seal is clean and unobstructed to keep cold air from escaping
• Clean inside with a damp cloth every week
  • Use sodium bicarbonate (baking soda) dissolved in lukewarm water to clean anything dirty
  • Allow inside to dry before closing lid and putting away
• Do not use detergent, soap, or abrasive/sharp products
• Never clean under running water
• Do NOT store the unit on its side. Always keep it upright to prevent damage to the compressor

“Fahrenheit” Power-On Bug

Idle Compressor (Temp set to -4F)

When my former coworker received the freezer, he complained that he did not know how to change the temperature display to show Fahrenheit instead of Celsius. We were able to find out how to enter Programming mode (see PROGRAMMING section above), cycled to “C”, and changed it to “F”. The values were now showing in Fahrenheit.

When I powered off and unplugged the freezer to take some photos for this review and later plugged it back in, the compressor would not turn on (both the “Power” and “Set” LEDs were Red).

• From my Foho BCD52 experience, I knew there would be a time delay that would keep the compressor off until 3 minutes had passed since power on
  • I waited… for 50 minutes. Nothing happened
• Target temperature was set to -4F (-20C), but the LCD steadily climbed towards 50F (10C)
• Double-checked that all settings were Default values
• Checked the setting again and changed F back to C (Celsius). Suddenly, the “Set” LED turned Green and the compressor turned on

I dismissed that oddness as a one-time fluke and went on to collect more information and photos for this review. Then it happened again. The compressor would not turn on, both the “Power” and “Set” LEDs remained Red, and the internal temperature continued to climb for the next 30 minutes. I dug deeper and found the culprit.

BEFORE YOU CHANGE TO FAHRENHEIT: I strongly suggest you do NOT change to Fahrenheit at this time.

[Update 7/19/2020: I’ve been contacted by a few individuals that changing their car freezers to Fahrenheit caused unexpected cooling behavior. One of my friends even bricked hers (compressor would no longer turn on at all). In addition, Rockpals’ response to a customer’s review on Amazon was: “It isn’t recommended to change into F or your fridge would be ruined.” This all but confirms the bug I ran into during testing. Until Rockpals finds a fix, I strongly suggest you do NOT change to Fahrenheit at this time.]

CRITICAL BUG: When car freezer is set to operate in Fahrenheit, the compressor would NOT start when powering the Rockpals on, even after waiting for 30 minutes. It also does not auto resume power when simulating an outage by yanking and replacing the AC plug. Refer to the video.

The Workaround

Change the setting to display Celsius, the factory default. Compressor consistently turned on after:

• Power on and time delay protection period passed
• Simulated power outage when “Auto Resume” functionality restored power

I shared the finding (and video) with Rockpals support. As long as the temperature unit is left at Celsius, the car freezer worked reliably.

Defrosting and How Refrigerators Work

I was fortunate (or unfortunate) to troubleshoot our home refrigerator a few years ago when it could not keep food frozen nor items cool in the fridge section, resulting in nearly a thousand dollars in lost food and medication… twice. Sears technicians were useless and considered the unit a total loss. After having spent months researching and learning, I gained an understanding of how refrigerators work and fixed it myself. (If you are curious, 2 thermistors needed to be replaced at a couponed cost of $86.)

• A refrigerator unit consists of two compartments: freezer and refrigerator (for drinks, fruit, veggies, etc.)
• Freezer pushes cold air into the fridge section via a fan, and the warmer air from the fridge is returned to the freezer for cooling
  • If the freezer fails, so will the fridge
• The compartments each have a thermistor (a resistance thermometer) to sense how cold both sections are
• Compressor (and associated fan) is turned on or off as needed to maintain the temperatures
• Over a long time, as you keep opening the door and let warmer air enter the freezer, the air moisture turns into frost/ice along the walls and shelves
  • Cooling efficiency diminishes and could spoil food faster when safe temperatures cannot be maintained
  • Frost build-up reduces available freezer space
• For optimal efficiency, you should defrost the freezer at least once a year by unplugging the appliance and letting the ice melt off the sides and shelves
  • Have a towel ready to soak up the melted water and wipe dry the sides before turning it back on
• Today’s refrigerators have an auto-defrost cycle where heat is applied to the freezer’s evaporator coil (which is responsible for cooling)
  •  Melted water leaves the freezer and is evaporated by a fan
  • Cycle can occur once or multiple times a day, resulting in fluctuating temperatures
• Auto-defrosting freezers cost more, use more energy, make more noise, but requires less maintenance

The Rockpals car freezer does NOT have an auto-defrost cycle (nor was I immediately able to find any portable ones that do), and so requires occasional, manual defrosting when used for an extended period of time. Because it does not have two thermistors and separately enclosed freezer and chiller sections, they cannot have their temperatures individually controlled. As such, items in the chiller could freeze over time as the cold air travels over from the freezer section.

I set the temperature to -4F for a test and left a water bottle in each compartment. Within a few hours, the freezer bottle froze (-4F) and the other was merely cold (18F). The chiller bottle became frozen overnight, however, since 18F is below freezing.

Final Thoughts

Credit: Rockpals

The Rockpals RP-25L is the company’s first foray into the car freezer space. At 26 quarts, it makes for a portable refrigerator/freezer that can be operated through an AC outlet, car cigarette port, and battery power station, making it perfectly suitable for long errand runs, such as grocery shopping, and picnics at the park. In normal, ambient temperatures, it can quickly drop the internal temperature to freezing and keep it at that level with its insulated walls. It has a very commanding, professional look, but the bright, blue LCD and loud “Dings” when a button is depressed can make it unsuitable for environments that require silence or darkness. It is quite power efficient and had worked reliably in keeping my wife’s ice cream birthday cake solid frozen during the time I had it available.

The only gripe I have with this freezer is that it does not operate as expected when the temperature is set to display Fahrenheit instead of Celsius, a problem for the American market. For that very reason, I lowered the Design score from 80% to 50% until the issue is fixed. Meanwhile, remember this:

• Freezing temperature is 0C (32F)
• Frozen food should be at -18C (0F) or below
• Refrigerated food should be at between 0C – 5C (32F – 40F)

A great, first attempt at a car freezer, Rockpals, although I hope your engineering team will be able to figure out a solution to the “Fahrenheit” bug. With that said, I recommend the Foho freezers over this Rockpals by far, such as the Foho BCD-52 (55 qt). Please read my review of the smaller 34qt Foho BCD-32.

Where To Buy

• Rockpals RP-25L Car Freezer (26 Qt)

Related Reviews

• Car Freezers
  • Costway EP24413/24413-CYPE (53qt) Dual-temperature
  • Foho BCD-52 (55qt) / BCD-32 (34qt)
  • Domende HC-50 (54qt)
• Car Freezers with Battery
  • Acopower LiONCooler X40A (42qt) with Solar charging
  • Bodega Cooler Mini P15 (16qt) with 2 Battery Slots