As promised, here's my battery usage test comparing the run time of a Vitrifrigo fridge/freezer on both 12-volts DC as well as through a 120-volt AC inverter. (rerun January 2023)
THANKS, Mike! This answers a lot of questions for me.
Currently, (pun intended) I have a 280AH LiPO4 battery and quite a lot of solar panels powering it. I run my chest refrigerator/freezer 24/7, as well as my CPAP all night long. This has made boondocking so much better for me. At present, I just have a cheap voltmeter, which also has some sort of % reading, as well. Only after multiple, poor solar days does the reading fall below 13v and 90% I have just bought an additional 280Ah battery, which has an actual Bluetooth capable monitor built in. I'm hoping that will help me more closely monitor my lower use.
I have a 2k inverter, and I am considering adding a 120v apartment size refer, which I think consumes @ 100w. Do you think I'm in danger of drawing too much power, as thus would require leaving my inverter on full time ?
I have a battery-draw readout on my power panel, and my Novakool fridge (9cuft) draws about 5A while running on battery. It has the Danfoss cooling unit, and I have it set to high-draw with the series resistor.
When I flip it over to 120V, off my AIMS inverter powered by the same battery, the draw goes to 5.5A.
The AIMS inverter is rated at >90% efficiency, so this all makes sense.
But your efficiency numbers -- basically 54hr down to 32hr -- are far worse. Why is that?
I'm going though two conversions at 120 volts with this setup. The Vitrifrigo fridge is 12-volts DC only. So to use the 120-volt AC outlet on the Jackery I have to plug in a 120-volt to 12-volt power supply brick. That means I'm converting 12-volts DC from the Jackery to 120-volts AC, then converting 120-volts AC to 12-volts DC to power the Vitrifrigo. Plus the Jackery doesn't have the fan on while supplying 12-volts DC. But as soon as I engage the inverter it turns on an internal fan. Is your 12-volt DC test with the AIMS inverter powered off? I've found that many inverters usually have a least 10-watts of overhead for the fan and control electronics that only becomes relevant when supplying low wattage loads. Also, the lower the duty cycle of the load, the higher the total overhead Wh as a percentage of energy usage.
So I assume a fair amount of my efficiency loss was due to inverter overhead which wasn't happening when the Jackery was only supplying 12-volts DC. At least that's my SWAG...
I chose the AIMS unit because of its low idle draw. Less than 1A, about consistent with your 10W number. And yes, it was off for the 5A number and on for the 5.5A number. That doesn't jive with a 0.8A idle current, does it? So I think my numbers might be slightly off, precision-wise. Also, there's an upside-down possibility: does the Danfoss compressor itself run on 12V or 120V? If the latter, then there's a small internal loss there that's inverse to our outside conversion factors. It takes a sharper pencil than I've used yet. If you need better measurements, let me know and I'll try to get some improved numbers. Unfortunately, my setup is real-life, real-time, not a lab, so I don't know how much better I can do.
Actually, for this test the fridge/freezer was empty. Since I set the temperature to -7F I didn't want to leave my beer in there. 🍺🍺
However, I could easily do a followup test at +34% F loaded up with bottled water. Perhaps that would be a more real-world demonstration. What do you think?
THANKS, Mike! This answers a lot of questions for me.
Currently, (pun intended) I have a 280AH LiPO4 battery and quite a lot of solar panels powering it. I run my chest refrigerator/freezer 24/7, as well as my CPAP all night long. This has made boondocking so much better for me. At present, I just have a cheap voltmeter, which also has some sort of % reading, as well. Only after multiple, poor solar days does the reading fall below 13v and 90% I have just bought an additional 280Ah battery, which has an actual Bluetooth capable monitor built in. I'm hoping that will help me more closely monitor my lower use.
I have a 2k inverter, and I am considering adding a 120v apartment size refer, which I think consumes @ 100w. Do you think I'm in danger of drawing too much power, as thus would require leaving my inverter on full time ?
If you look at my Lithium voltage chart you can see that 13.0 volts is around 40% to 50% State of Charge. https://open.substack.com/pub/rvelectricity/p/lithium-battery-discharge?r=1txmtl&utm_campaign=post&utm_medium=web&showWelcomeOnShare=true
Mike, FYI...
I have a battery-draw readout on my power panel, and my Novakool fridge (9cuft) draws about 5A while running on battery. It has the Danfoss cooling unit, and I have it set to high-draw with the series resistor.
When I flip it over to 120V, off my AIMS inverter powered by the same battery, the draw goes to 5.5A.
The AIMS inverter is rated at >90% efficiency, so this all makes sense.
But your efficiency numbers -- basically 54hr down to 32hr -- are far worse. Why is that?
I'm going though two conversions at 120 volts with this setup. The Vitrifrigo fridge is 12-volts DC only. So to use the 120-volt AC outlet on the Jackery I have to plug in a 120-volt to 12-volt power supply brick. That means I'm converting 12-volts DC from the Jackery to 120-volts AC, then converting 120-volts AC to 12-volts DC to power the Vitrifrigo. Plus the Jackery doesn't have the fan on while supplying 12-volts DC. But as soon as I engage the inverter it turns on an internal fan. Is your 12-volt DC test with the AIMS inverter powered off? I've found that many inverters usually have a least 10-watts of overhead for the fan and control electronics that only becomes relevant when supplying low wattage loads. Also, the lower the duty cycle of the load, the higher the total overhead Wh as a percentage of energy usage.
So I assume a fair amount of my efficiency loss was due to inverter overhead which wasn't happening when the Jackery was only supplying 12-volts DC. At least that's my SWAG...
I chose the AIMS unit because of its low idle draw. Less than 1A, about consistent with your 10W number. And yes, it was off for the 5A number and on for the 5.5A number. That doesn't jive with a 0.8A idle current, does it? So I think my numbers might be slightly off, precision-wise. Also, there's an upside-down possibility: does the Danfoss compressor itself run on 12V or 120V? If the latter, then there's a small internal loss there that's inverse to our outside conversion factors. It takes a sharper pencil than I've used yet. If you need better measurements, let me know and I'll try to get some improved numbers. Unfortunately, my setup is real-life, real-time, not a lab, so I don't know how much better I can do.
Was the fridge empty or full? I often hear that a full fridge requires less energy, but never seen real world proof /tests.
It may be a good follow up test. 👍
Actually, for this test the fridge/freezer was empty. Since I set the temperature to -7F I didn't want to leave my beer in there. 🍺🍺
However, I could easily do a followup test at +34% F loaded up with bottled water. Perhaps that would be a more real-world demonstration. What do you think?
Be nice to have a real world answer to this. Thanks.