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paulz
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# Posted: 22 Oct 2023 09:39
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Quoting: ICC 1.5 amps at 115 volts AC.
Ah, AC only. I only use my inverter a bit, big screen TV, washing machine, dog clippers.. Are they really inefficient to use all day and night?
Water pump, fridge, lights all 12v.
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Nobadays
Member
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# Posted: 22 Oct 2023 09:49
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Quoting: paulz Are they really inefficient to use all day and night?
If you mean inverters..... yes and no. Cheaper ones, to my knowledge generally have no "Eco mode" as Victron calls it. What this does is if it detects no load it goes to standby, then every few seconds it wakes and looks if there is a load if not back to standby. Using far less power at idle.
The other consideration is size of inverter, the larger the more idle power consumed.
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gcrank1
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# Posted: 22 Oct 2023 14:14
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That 1.5amps @ 115 (better to call it 120)vac will translate to more like 20amps/hr (c/w an inverter) from the 12v bat-bank.
The cycling with a compressor unit may drop that?
Iirc I decided Id need to at least double my bat-bank which would then require more recharging capability, but mine was 200ah 12v bat-bank with 600w solar (admittedly a pretty small system); not worth it to us part timing recreationally.
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Nobadays
Member
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# Posted: 22 Oct 2023 17:12
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Quoting: gcrank1 The cycling with a compressor unit may drop that?
I memory serves I believe you use 8hr/day for draw on a fridge because they do not run continuously. The important thing is to keep fridge and freezer full as dead air takes a lot of energy to cool.
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paulz
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# Posted: 22 Oct 2023 19:00 - Edited by: paulz
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Quoting: Nobadays you mean inverters..... yes and no. Cheaper ones, to my knowledge generally have no "Eco mode" as Victron calls it. What this does is if it detects no load it goes to standby, then every few seconds it wakes and looks if there is a load if not back to standby. Using far less power at idle. The other consideration is size of inverter, the larger the more idle power consumed
Here’s mine. Cheapo EBay, some years old but does the job. No Eco switch, just off n on. ‘Flamezum’, what a name for electronics..
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gcrank1
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# Posted: 22 Oct 2023 19:56 - Edited by: gcrank1
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It could be that it will power the rated 2500W 'continuous' but Id doubt the 5000W 'peak'.
Ive come to think of the continuous rating as the peak on that class of import. Just me....cautious/skeptical.
Ymmv
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Nobadays
Member
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# Posted: 22 Oct 2023 20:17 - Edited by: Nobadays
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Quoting: paulz ‘Flamezum’, what a name for electronics..
Sweet! Keep an extinguisher handy!
I looked up the specs and it says .9A-2A per hour idle draw.
Edit... 12w - 24w per hour
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Brettny
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# Posted: 22 Oct 2023 20:49
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I have a Xantrax inverter but everything I run wont wake it up from the sleep mode. I believe its 60w, so when I'm here its on, so is the fridge.
I'm on day 2 of clouds but cant figure anything out about run time because when I'm working on the cabin and the generator is running the battery bank is charging.
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paulz
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# Posted: 22 Oct 2023 21:28
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Quoting: Nobadays Sweet! Keep an extinguisher handy
It came with one..
It has a loudish fan that comes on only under a fair load (1000w+). TV won’t do it. It has powered down on clothes dryer start a couple times. I finally taped over the dryer door switch so I could give it an arm spin while starting.
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paulz
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# Posted: 23 Oct 2023 14:20
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Quoting: gcrank1 That 1.5amps @ 115 (better to call it 120)vac will translate to more like 20amps/hr (c/w an inverter) from the 12v bat-bank.
1.5A at 120v is 20A at 12v? I thought only watts depended on volts?
Been about 50 years since my last electrical class…
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ICC
Member
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# Posted: 23 Oct 2023 15:10 - Edited by: ICC
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1.5 amps x 120 volts = 180 watts. It does not matter if it is DC or AC, the math is the same
Then 180 watts ÷ 12 volts = 15 amps
But if you were using a 12 vdc inverter to supply 120 vac and were using 1.5 amps at 120 volts, then because of the inverter losses you would be using more DC amps than 15. Maybe 18 or so? Round that up to 20 to be safe.
Volts x Amps = Watts
Watts ÷ Amps = Volts
Watts ÷ Volts = Amps
-Izzy
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gcrank1
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# Posted: 23 Oct 2023 15:27
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Thanx for that Izzy 
I tend to over est draw and under est solar charging; just seems to match my real-world better.
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ICC
Member
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# Posted: 23 Oct 2023 15:31
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Better safe than sorry, or something like that
-Izzy
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paulz
Member
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# Posted: 25 Oct 2023 18:25
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Finally sinking in, this volts/amps relationship..
My solar readout says 64.6 volts and .4 amps, 26 watts for the array output (overcast today). Next to that is the output to the bank, 13.2 volts and 2.1 amps, 27 watts.
I knew the volts x amps = watts formula of course, just never dawned on me that if you had 12/120 fridge with the same motor (wattage), it take a lot more amps for 12v operation.
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Nobadays
Member
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# Posted: 25 Oct 2023 18:57
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I think what your MT50 shows is your mppt charge controller taking the excess voltage and using it to create more amperage for charging. That there is just magic!
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gcrank1
Member
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# Posted: 25 Oct 2023 19:17
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Yep, Paul, you got it now. Thats why so much of diy elec power is talked about in watts. Then you just divide by the volts of your bat-bank to figure the amps used and round up.
For us old motorheads who kinda think in 12vdc systems, or 24vdc if used to big trucks or equipment it is a jump.
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scott100
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# Posted: 25 Oct 2023 22:09 - Edited by: scott100
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Back when I looked at fridges for our cabin, I looked at "solar" rated fridges (efficient and expensive), propane fridges, small dorm fridges and standard ones. At the time, I came to the conclusion that a 10.1 cubic ft Magic Chef from HD, was more efficient than the smaller dorm fridges I found. The specs claim 297 kwh per year. By my calculations, that comes down to about 34 amp hours per day on my 24v system (plus any inverter losses). That's pretty efficient for a fridge that's apartment sized and is no issue with our solar setup. I'm not here throughout the winter, though, but if I were, I expect the generator would be used a bit more.
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Nobadays
Member
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# Posted: 26 Oct 2023 09:09
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Quoting: scott100 10.1 cubic ft Magic Chef from HD,
This is what we have been using for 4 years now.... I had put a Kilawat meter on it and though I can't remember what it was, but I remember it used even less power than the specs read. A good little fridge, though it is bigger than dorm size. We do have an LP fridge as well for drinks and overflow, and freezer space.
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Brettny
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# Posted: 26 Oct 2023 09:58
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Quoting: Nobadays I think what your MT50 shows is your mppt charge controller taking the excess voltage and using it to create more amperage for charging. That there is just magic
Not magic..just Ohms law
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paulz
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# Posted: 1 Nov 2023 12:36
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Just read the thread on first frost. None here yet on west coast, saw a 39F briefly the other morning.
Been thinking about moving my 12v mini fridge outside. Usually a 25 degree difference between outside and what I have the wood stove putting out in the cabin. We only go in it about twice a day, and by the side door would be almost as close as now.
Probably cut down on my electric load some, so why not?
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gcrank1
Member
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# Posted: 1 Nov 2023 12:41
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Yes, it is the temp differential that the unit has to achieve; hotter it is the harder it works.
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paulz
Member
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# Posted: 3 Nov 2023 10:38
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Thanks. Well I moved the little 12 volter outside two days ago. Ergonomically it’s fine, closer to the bbq in fact. Will it save much power? Hard to say with the varying solar power, use of other electrical things (Clint Eastwood night last night on TV), but it must be, 20-25 degree cooler in temp out there. So I’ll stick with it awhile longer. In the summer temps will be closer to equal. And when I do graduate to a larger LP unit, that will likely go outside too.
Here’s what I’m using. Friend gave it to me long ago.
https://img.saleyee.cn/Resources/GoodsAttachment//2021/202101/202101282127215709_988f 6568-6c38-46c9-8450-a30f21f22635.pdf
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gcrank1
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# Posted: 3 Nov 2023 12:05 - Edited by: gcrank1
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At our old off-grid cabin I had a small upright fridge with a dead compressor on the north side. Once we started getting pretty consistent temps under 40*f temps in the daytime the night temps were below freezing. I stuck a little thermometer in and when it seemed to stabilize about 36* we started using it as the fridge.
That worked until we got pretty cold and stuff started to ice up over night. Then we could put warm leftovers in for a while which would moderate the temp.
That gave us an easy to manage two shoulder seasons functional fridge without power at all.
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