Refrigerator Advice Please

[Kajtek1]

For anyone considering propane this is exhaustive.

https://www.hackneys.com/travel/docs/propane4xvehicles.pdf

bill

Nice article even as stated - written by non-professional.
Major error I found in that he calls DOT containers a tank, when proper nomenclature is cylinder.
To make it clear- tank is something permanently attached, when cylinders are portable.

 

[elemental]

Speaking of refrigerator efficiency, here is a chart showing efficiency by volume for the Isotherm Cruise Elegance (thicker door, more efficient) front-loading cabinet line:

Model (volume in liters)	energy consumption (watt-hours in 24 hours)	24-hour watt-hours/liter	Danfoss/Secop compressor type
CR EL 42	285	6.79	BD1.4F
CR EL 49	265	5.41	BD35F
CR EL 65	275	4.23	BD35F
CR EL 85	368	4.33	BD35F
CR EL 130	418	3.26	BD35F

Data is from Isotherm using these measurement controls: Power consumption Watts/24 h in operation on 12 V with +5°C (+41°F) in the refrigeration space, ambient temperature +25°C (+77°F) according to the Standards ISO 15502:2005 and EN 153:2006

Interestingly enough, power consumption is not linear with respect to volume; larger volumes generally provide more efficiency per unit of volume (except for the interruption in the trend for the Cr EL 85 for some reason). Compressor type makes a difference, too; the 49 liter unit has better power consumption than the 42 liter unit, probably due to the different compressor.

The DC-only Isotherm models with the BD35F or BD50F compressors (capable of variable speed operation) can have a "Smart Energy Controller" device added (purchased separately) to reduce battery battery consumption in cases where the refrigerator is operated part-time on battery only, and part-time with a charging voltage (from vehicle alternator, solar PV panels, generator).

I'm in the middle of testing the "Smart Energy Controller" out on a Cruise Elegance 130 to see whether it really works. According to the manual, when set to "Automatic" energy-saving operation it uses 2 energy modes (high energy mode when high voltage indicates non-battery power source, low energy mode when voltage indicates battery-only power source) to control the temperature setting and compressor speed(s). In high energy mode it runs the compressor at full speed (when calling for cooling) and lowers the internal temperature set point to +33.8°F. In low energy mode it lets the internal temperature float up to a pre-configured set point (one of +37.4, +39.2, +41, or + 42.8), and it runs the compressor at variable speeds according to need (unless the internal temperature rises to a pre-determined level above the configured set point).

The claim is that when better-than-battery power is available (high voltage) it's going to cool the interior and contents off to a point above freezing, but much colder than usual, as a kind of cold cache using the contents as the reservoir. When only battery energy is available, it a) coasts along using the colder than normal contents to keep the temperature down until it gets up to the pre-configured "normal" set point, and b) runs the compressor at variable speeds (reducing energy consumption) until/unless the interior temperature rises too high (then it runs the compressor at full speed only). The variable speed operation suggests it's at least a proportional control system (rather than bang-bang/on-off) and the manual hints that it is more than just proportional but provides no details. Isotherm claims it reduces battery consumption by 35% to 50%.

Although the variable speed compressor operation and possibly "better than proportional" control system might make it more efficient when running always on just battery power, it seems intended to make the most of a periodic charging source being available (like daytime solar PV, or running an engine/generator for a while).

I'm capturing baseline data right now (no smart controller, just the normal refrigerator controls), then I have to install/tune the smart controller before I can capture data showing an efficiency difference (if any).

[Edit: revised column titles]

 

[marklg]

Speaking of refrigerator efficiency, here is a chart showing efficiency by volume for the Isotherm Cruise Elegance (thicker door, more efficient) front-loading cabinet line:

Model (volume in liters)	24-hour power consumption	24-hour watts/liter	Danfoss/Secop compressor type
CR EL 42	285	6.79	BD1.4F
CR EL 49	265	5.41	BD35F
CR EL 65	275	4.23	BD35F
CR EL 85	368	4.33	BD35F
CR EL 130	418	3.26	BD35F

Data is from Isotherm using these measurement controls: Power consumption Watts/24 h in operation on 12 V with +5°C (+41°F) in the refrigeration space, ambient temperature +25°C (+77°F) according to the Standards ISO 15502:2005 and EN 153:2006

Interestingly enough, power consumption is not linear with respect to volume; larger volumes generally provide more efficiency per unit of volume (except for the interruption in the trend for the Cr EL 85 for some reason). Compressor type makes a difference, too; the 49 liter unit has better power consumption than the 42 liter unit, probably due to the different compressor.

The DC-only Isotherm models with the BD35F or BD50F compressors (capable of variable speed operation) can have a "Smart Energy Controller" device added (purchased separately) to reduce battery battery consumption in cases where the refrigerator is operated part-time on battery only, and part-time with a charging voltage (from vehicle alternator, solar PV panels, generator).

I'm in the middle of testing the "Smart Energy Controller" out on a Cruise Elegance 130 to see whether it really works. According to the manual, when set to "Automatic" energy-saving operation it uses 2 energy modes (high energy mode when high voltage indicates non-battery power source, low energy mode when voltage indicates battery-only power source) to control the temperature setting and compressor speed(s). In high energy mode it runs the compressor at full speed (when calling for cooling) and lowers the internal temperature set point to +33.8°F. In low energy mode it lets the internal temperature float up to a pre-configured set point (one of +37.4, +39.2, +41, or + 42.8), and it runs the compressor at variable speeds according to need (unless the internal temperature rises to a pre-determined level above the configured set point).

The claim is that when better-than-battery power is available (high voltage) it's going to cool the interior and contents off to a point above freezing, but much colder than usual, as a kind of cold cache using the contents as the reservoir. When only battery energy is available, it a) coasts along using the colder than normal contents to keep the temperature down until it gets up to the pre-configured "normal" set point, and b) runs the compressor at variable speeds (reducing energy consumption) until/unless the interior temperature rises too high (then it runs the compressor at full speed only). The variable speed operation suggests it's at least a proportional control system (rather than bang-bang/on-off) and the manual hints that it is more than just proportional but provides no details. Isotherm claims it reduces battery consumption by 35% to 50%.

Although the variable speed compressor operation and possibly "better than proportional" control system might make it more efficient when running always on just battery power, it seems intended to make the most of a periodic charging source being available (like daytime solar PV, or running an engine/generator for a while).

I'm capturing baseline data right now (no smart controller, just the normal refrigerator controls), then I have to install/tune the smart controller before I can capture data showing an efficiency difference (if any).

I'm a little confused with your data. Power is an instantaneous number measured in Watts. Energy is usually measured in Watt hours. 10 watts average for 24 hours is 240 Watt hours. Are you actually measuring Watt hours in a 24 hours time period? My Vitrifrigo 115 liter fridge used 564 Watt hours with 38 degrees in the refrigeration space and a 75 degree ambient. That is a little more than your 130 if you are also measuring Watt hours, but certainly in the same ballpark. So the column labeled "power consumption" seems reasonable if it is actually "energy consumption in watt hours for a 24 hour period".

Regards,

Mark

 

[elemental]

So the column labeled "power consumption" seems reasonable if it is actually "energy consumption in watt hours for a 24 hour period".

I handmade the table after a simple copy of the IndelWebasto (Isotherm) table failed to paste into the forum, then spent too much time getting the rest of the details in the post right. The data in the post table comes from the company table (except for the 24-hour watts/liter column), and the company's title for the column is "Power consumption (W/24 hours)". Since I didn't pay enough attention to the column title, it ended up "24-hour power consumption". In my personal data table, I've been avoiding clumsy nomenclature by dividing the total watt-hours (measured by a Kill-a-watt meter on the 110VAC I have running into my 12VDC power supply) by the run time to get the average power consumption (in watts) during operation. Your suggestion is a better title for the column, and I'll update the title of that column and the subsequent one accordingly.

 

[marklg]

I handmade the table after a simple copy of the IndelWebasto (Isotherm) table failed to paste into the forum, then spent too much time getting the rest of the details in the post right. The data in the post table comes from the company table (except for the 24-hour watts/liter column), and the company's title for the column is "Power consumption (W/24 hours)". Since I didn't pay enough attention to the column title, it ended up "24-hour power consumption". In my personal data table, I've been avoiding clumsy nomenclature by dividing the total watt-hours (measured by a Kill-a-watt meter on the 110VAC I have running into my 12VDC power supply) by the run time to get the average power consumption (in watts) during operation. Your suggestion is a better title for the column, and I'll update the title of that column and the subsequent one accordingly.

Sounds OK. So these are not your measurements, they come from the company? That makes sense as they are in the ballpark but seem a little low. If you make your own with a kill-a-watt, I bet it will be somewhat higher. It seems that solar panel makers, fridge makers and air conditioner makers measure at exactly the right phase of the moon while standing on one leg, and no one else can duplicate their numbers. Maybe they hand make the unit they measure with and then the ones that go down the normal production line don't quite measure up.

Don't get me wrong, the Secop compressors are great, and why I switched from an absorption fridge to a compressor fridge. They just aren't quite as good as advertised.

Yeah, I'm pretty cynical, but that seems to be true. I've never seen a solar panel that met it's published numbers. I'm in Arizona with sun straight overhead and severe clear and I get max 85% or so of what they say for good ones, 60% for the crap. I expect the fridge fudge factor is similar.

Regards,

Mark

 

[gltrimble]

Your power consumption table is accurate. I have the Isotherm 130 and my power consumption averages under 1.5 amps/hour or about 400 watts/24 hours. And yes, the larger Danfoss equipped units are more efficient when measured by watt-hours/liter of capacity. Even more efficient than most chest coolers.

Your summary of the Smart Energy Controller is also accurate. It just cycles the thermostat. I prefer cold beer so I just leave my fridge set to 35F or colder.

 

[elemental]

Sounds OK. So these are not your measurements, they come from the company? That makes sense as they are in the ballpark but seem a little low. If you make your own with a kill-a-watt, I bet it will be somewhat higher. It seems that solar panel makers, fridge makers and air conditioner makers measure at exactly the right phase of the moon while standing on one leg, and no one else can duplicate their numbers. Maybe they hand make the unit they measure with and then the ones that go down the normal production line don't quite measure up.

Yes, the data in the table is from Isotherm as their published numbers for those refrigerator models.

After the first 24 hours, my measurements are higher than the ones from Isotherm by about 50%. However, there are several factors that contribute to expected higher readings:

1. I had control set to "4", which I thought I read read in a manual would give me a 40 deg.F set point (not because 4=40, just because that was the set point for 40 degrees). 24 hours of operation at "4" resulted in my 8 or 10 oz. glass of water on the front of the middle shelf settling down to 36-37 deg.F as measured using a Thermoworks Thermapen Mk4 thermocouple-based quick read thermometer. That's quite a bit lower than the ISO standard 41 deg.F that Isotherm tested at.
2. I started measuring after only an hour of refrigerator operation at what I thought was the target temperature. I had let the unit run for about an hour, then stuck in pre-cooled soda cans (40 deg.F) for ballast and let it stabilize for another hour, then started measuring. I thought I was starting very close to the target temp, but found out over time that the actual control set point was going to settle at 36-37 deg.F. So some of that energy was getting down to the set point, as opposed to maintaining the set point.
3. I'm measuring using the Kill-a-watt on the AC input to a 12VDC power supply. Even when the refrigerator compressor is not running at all, the Kill-a-watt is showing a 5 watt draw; possibly some inefficiency in the power supply as well as whatever the refrigerator control circuitry draws at idle.

I've adjusted the control from "4" to "3" and I'm doing another 24 hour measurement period to see if I have the temperature dialed in about about 39-40 deg.F. Then I'll do a clean 24 hour baseline run. I'm doing this in the summer so that my ambient temperature will be in the neighborhood of the 77 deg.F of the ISO standards. I'm not going to do the 41 deg.F set point, however, because my actual aim is to measure the efficiency impact of the Smart Energy Controller, and it only has a few pre-set temperature set points; the one that is closest to my preferred 40 deg.F for long-term use is at 39.2. There is one at 41 as well, but I'm measuring for my intended use and not the ISO standard. I expect my numbers to end up slightly higher than the Isotherm ones. (I share your cynicism with respect to manufacturer's published results; having worked in high tech for decades, it seems the vendor's measurements are always a bit optimistic. That's why I'm measuring to predict my real world results.)

 

[marklg]

Yes, the data in the table is from Isotherm as their published numbers for those refrigerator models.

After the first 24 hours, my measurements are higher than the ones from Isotherm by about 50%. However, there are several factors that contribute to expected higher readings:

1. I had control set to "4", which I thought I read read in a manual would give me a 40 deg.F set point (not because 4=40, just because that was the set point for 40 degrees). 24 hours of operation at "4" resulted in my 8 or 10 oz. glass of water on the front of the middle shelf settling down to 36-37 deg.F as measured using a Thermoworks Thermapen Mk4 thermocouple-based quick read thermometer. That's quite a bit lower than the ISO standard 41 deg.F that Isotherm tested at.
2. I started measuring after only an hour of refrigerator operation at what I thought was the target temperature. I had let the unit run for about an hour, then stuck in pre-cooled soda cans (40 deg.F) for ballast and let it stabilize for another hour, then started measuring. I thought I was starting very close to the target temp, but found out over time that the actual control set point was going to settle at 36-37 deg.F. So some of that energy was getting down to the set point, as opposed to maintaining the set point.
3. I'm measuring using the Kill-a-watt on the AC input to a 12VDC power supply. Even when the refrigerator compressor is not running at all, the Kill-a-watt is showing a 5 watt draw; possibly some inefficiency in the power supply as well as whatever the refrigerator control circuitry draws at idle.

I've adjusted the control from "4" to "3" and I'm doing another 24 hour measurement period to see if I have the temperature dialed in about about 39-40 deg.F. Then I'll do a clean 24 hour baseline run. I'm doing this in the summer so that my ambient temperature will be in the neighborhood of the 77 deg.F of the ISO standards. I'm not going to do the 41 deg.F set point, however, because my actual aim is to measure the efficiency impact of the Smart Energy Controller, and it only has a few pre-set temperature set points; the one that is closest to my preferred 40 deg.F for long-term use is at 39.2. There is one at 41 as well, but I'm measuring for my intended use and not the ISO standard. I expect my numbers to end up slightly higher than the Isotherm ones. (I share your cynicism with respect to manufacturer's published results; having worked in high tech for decades, it seems the vendor's measurements are always a bit optimistic. That's why I'm measuring to predict my real world results.)

I tested for days, making small changes and adding insulation till I got the interior temp I wanted. I also like my drinks cold. Then I took measurements.

Most recently, I ran tests here in Phoenix. Above about 108 degrees ambient and higher in the van, the interior temp in the fridge started to rise. With the AC running in the van and those temps outside, it was fine. The absorption fridge would have given up way before then.

Regards,

Mark

 

[Graphite Dave]

I had a Dometic 80 liter front opening refrigerator in the sold Sprinter. Bought a 85 liter front opening Vitrifrigo for the Transit build. Same installation and same 255 amp-hr house battery. Much to my surprise the Vitrifrigo uses 1/3 less power than the Dometic. Believe the reason is the condenser design. Dometic had a coil on back of the refrigerator and Vitrifrigo uses a small radiator with a fan.

 

[Harrison5]

So far with our sprinter we are weekend warriors but just came off of a 9 day trip to Florida/Louisiana. I by no means would say that we are experienced van lifers but as a family of 5 we definitely know how to make it fun... lol! We purchased a cheap Alpicool T50 fridge/freezer combo ($369 12v) because I wanted to put it under the bench seat and it was the right size. Plus it had a freezer. It uses 3.4amps while running. The fridge worked fantastic on our 9 day trip. Everything stayed very cold even in the Florida heat and the van staying in the sun all day with only the Maxxair fan running to flow air in the van. I will say the freezer portion is a little deceiving as it will NOT freeze anything but will keep it mostly frozen. Because of that we decided to remove the divider and just keep the temperature of the fridge at 34 degrees and it does that very well. So far for the money spent it has worked really well.

 

[elemental]

I tested for days, making small changes and adding insulation till I got the interior temp I wanted. I also like my drinks cold. Then I took measurements.

Most recently, I ran tests here in Phoenix. Above about 108 degrees ambient and higher in the van, the interior temp in the fridge started to rise. With the AC running in the van and those temps outside, it was fine. The absorption fridge would have given up way before then.

I got the temperature dialed in close enough today and started my 24 hour baseline. Anecdotally it appears the interior temperature setting and ambient temperature are both sensitive factors for power consumption (not really surprising). I decided to track the variables on an hourly basis (except for overnight; no automatic logging facilities).

I'm planning on staying away from 100+ temps while traveling; got too much of that living in Maryland. I'll visit Arizona in the winter, spring, or fall.

 

[SSTraveler]

I have the Isotherm Cruise 219 with the BD50F compressor and always camp in +100° temps. I have my temperature setting on about 3- 1/4 and the temperature at the door stays right at 40-41°. The interior is more like 36°. I don't use the Smart controller and like Gltrimble, I see an average usage of 1.5a. I use about 40a per 24 hours, my 210ah AGM batteries and 200w of solar run my Refrigerator easily. I absolutely love my Isotherm. One thing I experience is the Refrigerator's back wall gets as cold as 21° and it cycles. So at times I see frozen beads of water on the back wall at other times water beads are seen slowly running down the back wall to the drain. I found if anything is touching that wall it will freeze solid, even a full gallon of milk. It's hard to keep things from sitting on the back wall, particularly when driving so I use these double Camco Refrigerator bars, https://www.amazon.com/Camco-Refrig...d=1597399274&sprefix=Camco+ref,aps,213&sr=8-2, lightly pressing on sides as not to deform the walls, to create a barrier to keep my liquids from freezing. Now all is good and nothing freezes. BTW my freezer stays at 0°. Your gonna love your new Isotherm, great choice!

 

[elemental]

I got the temperature dialed in close enough today and started my 24 hour baseline. Anecdotally it appears the interior temperature setting and ambient temperature are both sensitive factors for power consumption (not really surprising). I decided to track the variables on an hourly basis (except for overnight; no automatic logging facilities).

Well... best laid plans of mice and men, and all that. It took me longer than I wanted to get my refrigerator measurements to compare the standard analog controller and the SEC (digital) controller, and circumstances intervened and made my data collection not nearly as scientific as I envisioned.

The net result is that I observed the Isotherm SEC installed in my Isotherm Cruise Elegance 130 refrigerator to reduce battery energy consumption somewhere between 22% and 29% under testbed conditions. The reduction came while running on battery-only power levels in a 24-hour period with 8 hours charging power (supply voltage above 13.2 VDC) and 16 hours battery-only power (supply voltage below 13.2 VDC) [actual reduction experienced depends on how much inefficiency was present in the 120VAC to 12VDC power supply used during the test].

My rough measurements also suggest that power consumption during long-term operation on battery-only power may be slightly more with the SEC (digital controller) than the standard analog controller, but my testing did not have the necessary rigor to conclusively show this result.

The results are not rigorous because energy consumption with both controllers was very sensitive to the set point, ambient temperatures, and the thermal mass of the refrigerator contents. I maintained a consistent set point fairly well, maintained the same thermal mass (but with a slightly different distribution), but could not control the ambient temperature well between and during test runs. Unfortunately I was not able to include ambient temperature data during the collection of baseline data with the standard analog controller.

A higher thermal mass in the refrigerator would probably increase the battery energy savings as it would take longer for the internal temperature to rise during battery-only operation. A shorter period of "battery-only" operation (versus "charging" operation) would certainly increase the energy savings; it took 10 hours for the refrigerator to "coast" up to the 41°F set point, during which very little energy was consumed at all.

Method
I loaded my Isotherm Cruise Elegance 130 refrigerator (BD35 compressor) with twenty 16.9 fl. oz. water bottles and eight 12 fl.oz. soda cans (Coca-Cola if it matters). I measured temperatures in a glass of water that I located at the forward edge of the bottom wire shelf of two (above the vegetable draw top) at approximately the height that the SEC temperature sensor is installed. Only the factory insulation was used. The refrigerator was free-standing (not installed in a cabinet), but was protected from direct sunlight.

I measured electricity consumption using a 120VAC Kill-a-watt monitor at the input of a 12 VDC power supply that was in turn wired to the refrigerator power leads. My measurements are probably slightly high due to overhead/inefficiency in the 120VAC to 12VDC power conversion; I saw a fairly constant 5 watt load on the Kill-a-watt even when the compressor wasn't running. I'm don't know how much of that is the power supply versus parasitic load in the refrigerator.

Baseline with standard analog controller
I found that the standard analog control maintained approximately 41°F at a control setting of "2". I ran the refrigerator for a total of 62 hours 51 minutes after stabilizing the temperature, with a total of 1.26 kilowatt-hours recorded on the Kill-a-watt. That's 20.05 watts average usage, or about 40 amp-hours/day assuming 12 VDC. Unfortunately I did not manage to record the ambient temperatures, but they were fluctuating between 69 and 70-something degrees. If the 5 watt draw is all attributed to the power supply, then it it would be a 30.1 amp-hours/day at a nominal 12VDC.

SEC (digital) controller installation
After capturing this baseline with the standard analog temperature controller, I installed the Smart Energy Controller (digital). It was slightly harder than the many-year-old Isotherm video shows, partially because my refrigerator is a different model than the one used in the video, and partially because the video cuts out certain parts. I had to pull the capillary tube for the analog temperature sensor out from behind the refrigerator liner in the ceiling, not just pull it off the wall. It might be re-installable, but only with difficulty.

I briefly assumed that the SEC unit would have the DIP switches set for the "standard" refrigerator configuration as shown in the manual; this was not the case. All of the DIP switches were set to the "off"/0 position out of the box. Fortunately I checked them before installation, and I set them to:

• [Bat] 1 (V < 10.8),
• [VLS] 0 (13.2 VDC),
• [R/F] 0 (Refrigerator),
• [T/deltaT] 10 (Fridge mode "2", with T 41°F, and deltaT 50°F), and
• [Offset] 100 (offset "4", +8.1F).

Except for the [Bat] setting, this is the "standard" refrigerator configuration shown in my SEC manual. I wanted the [Bat] setting higher to protect my battery more (this resulted in a problem after installation - see the end of this for the reason why).

If someone installs the SEC without adjusting the all-zero DIP switch settings, they will probably get somewhat unsatisfactory operation and less energy savings as the refrigerator would try to maintain a 34.7°F temperature on battery-only, and possibly as low as 31.1°F when VDC > VLS ("cold storage" mode).

The suggested [Offset] was far too high for my refrigerator/SEC combination. I had to run the unit for two days, making incremental adjustments to the offset, until I achieved the approximately correct set point at [Offset] 001 (offset "1", 0°F). At this offset, my temperature measurements in "cold storage" mode were 33.5°F (only slight off from the nominal 33.8°F), and in "normal" mode (battery-only operation) about 41.3°F. At two times while making adjustments the refrigerator didn't start up properly after shutting it down, changing the [Offset], and starting it up again. Both times simply shutting the refrigerator off again (via the control dial), waiting some 10s of seconds, then starting it back up again cleared it up.

Measurement for SEC (digital) controller
My load/measurement setup was the same as for the standard analog control. I varied the my power supply voltage from 12.02 VDC (simulated battery-only operation) to 13.42 VDC (simulated "charging" operation).

I started my data collection with the fridge in "cold storage" mode and temperature stablized at 33.5°F. In hindsight, I should have started it at the battery-only mode set point of 41.3°F in order to capture the energy usage while reducing the temperature to the "cold storage" set point. I ran the refrigerator for an 8 hour period as if it were in charging mode (13.42 VDC supply), then I changed the voltage to battery-only mode (12.02 VDC supply) for a 16 hour period. These were the results:

• First eight hours (VDC > VLS): this period average 33.7 watts (33.5*F temperature maintained)
• next ten hours (VDC < VLS): this period average 11.52 watts (temperature rose to 41.6*F)
• at 24 hour mark (VDC < VLS): overall average 15.64 watts (temperature was maintained at 41.2-41.4°F for the last 6 hours)

Results
Based on this 8-hour charge/16-hour battery duty cycle, then SEC reduced consumption during battery-only operation from 320.8 watt-hours (standard analog control) to 250.24 watt-hours (SEC control), a 22% reduction. It did this at an overall 25.38 watts (inclusive of charging period plus battery-only period) rate, which is higher than the 20.05 watt average for the standard analog control.

If the 120VAC to 12VDC power supply's inefficiency is responsible for the entire observed 5 watt consumption when the refrigerator was at idle, then the energy savings are more impressive, as the SEC would be reducing consumption during battery-only operation from 240.8 watt-hours to 170.24 watt-hours, a 29% reduction.

I then ran the refrigerator in battery-only mode (VDC < VLS) for a total of 52 hours (28 hours past the end of the first 24-hour period). I found that the average watts used after the initial warm-up to 41.6°F was 24.13 watts while maintaining the temperature at about 41°F (compared to only 20.05 watts average with the standard analog controller). This suggests that long-term operation on battery-only with the SEC may be less efficient than long-term operation on battery-only with the standard analog controller. However, poor control over the ambient temperature, differences in the way the refrigerator was reloaded (same content, but possibly arrange differently) may explain that difference - my data suggests that the energy usage is sensitive to ambient temperature, and may be somewhat sensitive to the loading.

Other findings
I installed the refrigerator in my van after completing all of my testing, the night before leaving for a 2-week trip. I was disappointed to find the refrigerator not working correctly. It would start up, run briefly, then shut down. After a brief pause, it would repeat the behavior. It did this continuously.

Troubleshooting revealed several issues:

• My branch circuit for the refrigerator is 12 AWG wire over an estimated 18-20 foot run (this circuit was not originally intended to run the refrigerator). The Blue Sea Systems circuit wizard suggests that a load of 2 amps (average consumption by the refrigerator) would have < 3% loss over 40 feet (round trip) with AWG 12 wire, but the refrigerator manual suggests that the maximum run for 13 AWG wire is 8 feet, and for 11 AWG cable is 13 feet (one way). Why?
  • I observed the peak load when the compressor starts up to be at least 80 watts (6.6667 amps at 12 VDC), and the actual peak is probably higher (load observed on Kill-a-watt meter during refrigerator testing may not see actual peak).
  • The Blue Sea Systems circuit wizard suggests that a load of 7 amps needs 10 AWG wire to have < 3% loss over 40 feet (round trip).
• The refrigerator's low-voltage cutoff ([Bat] setting) was set to 10.8 VDC, an increase from the "standard" setting of 9.6 VDC

Measuring circuit voltage while the refrigerator attempted to start up in the van was revealing. Before the refrigerator tried to start, it was at 13.28 VDC at the refrigerator's power leads. At peak load while starting, the voltage sagged below the 10.6 VDC low-voltage cutoff (more than 20% voltage drop). As soon as this happened, the refrigerator cut off the compressor, even though it was just in its startup phase. The fan ran briefly after the compressor, then stopped. The voltage returned to about 13.2 volts, and the cycle repeated.

I changed the [Bat] setting on the SEC to the standard 9.6 VDC, and hooked up an external battery charger to the house battery. The refrigerator started normally and ran correctly. It continued to operate correctly on battery power for my 2-week trip without the battery charger, just normal charging by the van's alternator. However, based on the observed peak draw during startup, I'm going to run my dedicated refrigerator circuit using 10 AWG wire to reduce the possibility that a low house battery SOC will render the refrigerator inoperative due to voltage sag at peak startup current draw. I'm also going to investigate an alternative wire routing that might reduce the total circuit length.

 

[MS42]

Yes, it works great. See my profile for a link to the installation.

Regards,

Mark

How do I find the link?

 

[RVBarry]

How do I find the link?

Click on his name, and then click again.

Profile is at https://sprinter-source.com/forums/index.php?members/73428/#about
Presumably it's the 'Website' link there.

 

[MS42]

Thanks!

 

[Kajtek1]

I just spend 3 days on my patio boat, who I converted similar way to Sprinter conversion.
Inverter, converter, combiner, microwave, cappuccino machine, porta-poty in changing room.
So I had older AC/DC refrigerator/freezer beside cooler and even at home running overnight it would not freeze bottle of water.
On the boat it was running whole day, when I would shut it off for about 8 hr at night and it was pretty miserable.
Don't know if the age of the unit is big factor, as refrigeration did not change technology much in last 20 years, but spending $1000 for new, similar unit is out of the question and I decided to buy 120V refrigerator and mount it on the boat.
Found 3.2 cu-ft unit with separate door for freezer and my amazon prime found me unit with damaged box for $179.
My hope is that during the day I can make some ice in it and use the ice for additional cooler when we take more food.
For couple of days it will mainly cool the beer and keep some sausage. For boat use, dry noodles and canned food work fine.
Will test it well within a month.

 

[marklg]

I just spend 3 days on my patio boat, who I converter similar way to Sprinter conversion.
Inverter, converter, combiner, microwave, cappuccino machine, porta-poty in changing room.
So I had older AC/DC refrigerator/freezer beside cooler and even at home running overnight it would not freeze bottle of water.
On the boat it was running whole day, when I would shut it off for about 8 hr at night and it was pretty miserable.
Don't know if the age of the unit is big factor, as refrigeration did not change technology much in last 20 years, but spending $1000 for new, similar unit is out of the question and I decided to buy 120V refrigerator and mount it on the boat.
Found 3. cu-fr unit with separate door for freezer and my amazon prime found me unit with damaged box for $179.
Will test it well within a month.

The new AC/DC refrigerators with the Secop / Danfoss compressors are a significant improvement. Our works great and will even freeze ice. It's way better than the absorption type (AC/DC/Propane) at higher outside temperatures. It cools down in a couple hours vs a day or more for the old one. I got one that fit the space for the old one exactly. If a particular space was not a requirement, I suppose I might have considered a cheap dorm type. I already decided that RV specific microwaves don't last that long and replaced it with a $39 microwave that fit. It's lasted as long now as the previous $200 RV microwaves. I do consider that a failed fridge is more of a problem than a failed microwave.

Regards,

Mark

 

[Kajtek1]

Can't go without a trip picture. Lake Powel.
The boat is having 30 amp alternator, so with 20 amp charging circuit power management is crucial. But I also carry 1000W inverter generator, who with its small size will fit in sofa backrest.
The generator would not run microwave alone, but having big inverter running off double battery bank, I run the oven on it, using generator with 30 amp converter as booster as inverter went into low voltage alarm after 3 minutes.
Smaller coffeemaker and oven run on inverter alone just fine.
Thanks Mark for newer units update. As I said, spending $1000 is not an option. Where did you find $39 microwave oven? I would like to find smaller one and preferably with mechanical timer, as reading digital display in full sun gets pretty hard.
I have big unit from the camper I parted, but it takes too much space.
I agree that you can bake potatoes and kielbasa at campfire, but warm beer sucks.

 

[Kajtek1]

I run 3-day test on the dorm-type Frigidaire I pictured above.
It draws 0.8-0.85 amp when running, what is impressive.
I tested it on my patio, who is reaching 110F in afternoon.
The freezer part froze 1l bottle of water after 3 hr, what is impressive, but refrigerator compartment would stay above 40F most of the time.
Those fridges don't have fans and thermostat is in the refrigerator part, so there is no way to divert more cooling to refrigerator part.
Also the refrigerator has condenser coils build into side walls, who were coming up to 130F on the afternoon.
The amazon "open box" unit did not work too well as fridge come pretty beaten up, so I am replacing it for different unit, but looks to me that this is the way to go for my boat.
In the mean time my friend bought camping-style fridge for $350 and I was pretty impressed with it holding 40 beers cold, when set under motorhome in 108F weather. It draw 2 amp.
But for my boat I value separate freezer very high and with small alternator the 0.8 v/s 2 amp is crucial.
Also the coils build-into the walls make maintenance much easier.