Herbie
Rendezvous Conspirator
As Promised, Power Consumption Data
Hello Everyone. As promised, I am publishing the results of my first round of testing the power consumption of the FP430 (43qt) Edgestar.
If anyone is curious to see the graphs, etc., the summary is here, and the complete data file is here, if you're really into looking at pages of data.
Here's the basic test setup:
I used a 15A laboratory power supply (set to 13.2VDC), in series with a high-current precision shunt to power the fridge via the DC input. A DMM w/ RS-232 output measures the voltage drop over the shunt, and I use that to calculate the current. In this case, 1A=1mV, so you can understand that the voltage drop is very small, less than the drop over an equivalent long set of power cables.
For my first test, I logged a reading every 15s for 24 hours. The fridge was set to 36F (keeping my root beer and water bottles cold but not frozen) and the room was thermostatically controlled to 72F. It's been cold here in SoCal this week, so this was the best I could manage. When the weather warms up, I'll repeat the test for 24hours in a locked car. I expect that power usage would obviously go up some, but you can see from the results that even with a significant increase in the compressor duty cycle, the fridge so far is looking pretty thrifty (for this steady-state condition). Obviously getting food in/out, putting in warm drinks to be cooled down, etc. is going to drive up the power budget, but the goal of this first test was to get a baseline for the "average" power consumption - much more useful than the peak current number alone.
An interesting note: With this setup, I can measure current as small as about 600 uA (or six-tenths of a milli-amp), so I was surprised to find that the idle current (compressor not running) was apparently even smaller than that, because when idling the text fixture reads zero. Now obviously it isn't really zero, but it's small enough I feel comfortable calling it "negligible".
OK, enough faffing about, here are the highlights:
Model: FP430
Peak Amps: 4.782
Compressor-On Duty Cycle: 16.67% (holding 36F at 72F ambient)
Total Amp-Hours (24H elapsed): 14.1151
Avg. "Amp-Hours per Hour": 0.58823
Now, the reason for doing all of this, and to put my money where my data is, I'll be using this to choose the house battery I'm about to order in my rush to get ready for Overland Expo. Based on the Total Amp-Hours consumed, I feel pretty confident that I can get away with a single AGM battery of around 85AH or so, since the one's I'm looking at actually measure out at over 100AH at a 100-hour draw rate. This should give me more than 72 hours of fridge operation and still keep to the recommended 50% discharge limit.
I hope someone else finds this useful, and I'll post back when I can run the test again in hotter weather.
Hello Everyone. As promised, I am publishing the results of my first round of testing the power consumption of the FP430 (43qt) Edgestar.
If anyone is curious to see the graphs, etc., the summary is here, and the complete data file is here, if you're really into looking at pages of data.
Here's the basic test setup:
I used a 15A laboratory power supply (set to 13.2VDC), in series with a high-current precision shunt to power the fridge via the DC input. A DMM w/ RS-232 output measures the voltage drop over the shunt, and I use that to calculate the current. In this case, 1A=1mV, so you can understand that the voltage drop is very small, less than the drop over an equivalent long set of power cables.
For my first test, I logged a reading every 15s for 24 hours. The fridge was set to 36F (keeping my root beer and water bottles cold but not frozen) and the room was thermostatically controlled to 72F. It's been cold here in SoCal this week, so this was the best I could manage. When the weather warms up, I'll repeat the test for 24hours in a locked car. I expect that power usage would obviously go up some, but you can see from the results that even with a significant increase in the compressor duty cycle, the fridge so far is looking pretty thrifty (for this steady-state condition). Obviously getting food in/out, putting in warm drinks to be cooled down, etc. is going to drive up the power budget, but the goal of this first test was to get a baseline for the "average" power consumption - much more useful than the peak current number alone.
An interesting note: With this setup, I can measure current as small as about 600 uA (or six-tenths of a milli-amp), so I was surprised to find that the idle current (compressor not running) was apparently even smaller than that, because when idling the text fixture reads zero. Now obviously it isn't really zero, but it's small enough I feel comfortable calling it "negligible".
OK, enough faffing about, here are the highlights:
Model: FP430
Peak Amps: 4.782
Compressor-On Duty Cycle: 16.67% (holding 36F at 72F ambient)
Total Amp-Hours (24H elapsed): 14.1151
Avg. "Amp-Hours per Hour": 0.58823
Now, the reason for doing all of this, and to put my money where my data is, I'll be using this to choose the house battery I'm about to order in my rush to get ready for Overland Expo. Based on the Total Amp-Hours consumed, I feel pretty confident that I can get away with a single AGM battery of around 85AH or so, since the one's I'm looking at actually measure out at over 100AH at a 100-hour draw rate. This should give me more than 72 hours of fridge operation and still keep to the recommended 50% discharge limit.
I hope someone else finds this useful, and I'll post back when I can run the test again in hotter weather.
I imagine that the competing fridges are probably a bit more efficient, overall - once you get the box down to temperature the first time, the steady-state duty cycle is more a factor of thermal mass and insulation. A more efficient compressor just means it should take fewer amp-hours to correct the delta T back to the set point - it shouldn't have to run more often unless for some reason it warms up quicker.
