Electrical system load measurements?

[imiceman44]

Nice! I'm getting pretty excited seeing these new AC units and actual fridge/freezers that will run with fairly minimal energy requirements. I'm tempted to buy one of the 12V fridges.

I've been running my house fridge the last couple of days off the 48V battery and about 300W of solar just to see what that looks like (not good lol, probably need 800W to account for clouds and charge enough to charge for the hours of darkness), being able to camp or even road trip with a 12V powered fridge/freezer that will run for days off a 12V 100Ah (or even 50Ah) battery to me is more interesting than a cooler with ice. Being able to recharge that setup with a 200W flexible panel means runtime would be near infinite.

What sort of run time improvement do you think you'll get from the new battery? I like this 48V, but at 80+ pounds, it's not exactly fun to move around. And being plastic cased, need to be careful about transport. I've seen a fair number of RV rooftop solar panel installs, they look pretty cool and would seemingly do quite well depending on where it was parked.

Let me know how your fridge does long term.
I am assuming you're not running a true sine wave inverter.
If you're running true sine then never mind.
I have a 4000w inverter but not sure I want to run a fridge on it.
I will run my water heater, lights even a TV.
I am thinking about I ut getting a 5000w true sine wave and use for motorized appliances.

 

[CyberSniper]

I run my house refrigerator on an APC SmartUPS all the time. It does bellyache when the defroster turns on (takes about 1000w all in) but the refrigerator motor keeps going. While most refrigerators do use a synchronous motor that really hates non-sine waveforms, they do OKish on close approximations (usually). A lot of the newer refrigerators are even using stepper motors for everything else so the ones that really get ****ed up like the ice maker and whatnot are no longer a problem.

A modern inverter will tell you how close it is on the spec sheet, but you can also scope it. In reality, any decent modern inverter will run a refrigerator.

To put things into perspective, I use a whole house Champion inverter generator. The whole thing cost $900 for 8000w of glory. Runs everything in the house fine. The freezer motor does complain a little but that's because it has a junk starting circuit. If you think about that, about $200 of that is probably the motor and chassis it is in. Another $150 for the electric "generator" to make 3-phase power and a rectifier back to knock it down with some capacitors to run it into the inverter. Then the standard inverter to make 220vac 1-phase power at 8kw. So you're talking maybe $550 for a inverter that does 8kw. That's pretty impressive. And I bought it before the pandemic.

 

[imiceman44]

I run my house refrigerator on an APC SmartUPS all the time. It does bellyache when the defroster turns on (takes about 1000w all in) but the refrigerator motor keeps going. While most refrigerators do use a synchronous motor that really hates non-sine waveforms, they do OKish on close approximations (usually). A lot of the newer refrigerators are even using stepper motors for everything else so the ones that really get ****ed up like the ice maker and whatnot are no longer a problem.

A modern inverter will tell you how close it is on the spec sheet, but you can also scope it. In reality, any decent modern inverter will run a refrigerator.

To put things into perspective, I use a whole house Champion inverter generator. The whole thing cost $900 for 8000w of glory. Runs everything in the house fine. The freezer motor does complain a little but that's because it has a junk starting circuit. If you think about that, about $200 of that is probably the motor and chassis it is in. Another $150 for the electric "generator" to make 3-phase power and a rectifier back to knock it down with some capacitors to run it into the inverter. Then the standard inverter to make 220vac 1-phase power at 8kw. So you're talking maybe $550 for a inverter that does 8kw. That's pretty impressive. And I bought it before the pandemic.

I know it will run, I am looking long term.
A motor will run but it will get hot, and long term could degrade an burn out.
It definitely will shorten it's life.
I also have other appliances and specifically a grain mill, and it's an expensive piece that I paid $300 for and now they are $800-900.
If they last 5-8 years it's fine, but if I burn it out in a couple of years then I will spend a couple of hundred dollars more and get sinewave

 

[dyeager535]

I ran the fridge for about three days. It is a 2000w true sine wave inverter, at least according to the specs and tests done on YouTube.

One thing I hadn't considered is what if the inverter faults? With your home electric you know if power goes out if you are home. Even if it comes back on microwave clock will be flashing etc., so at least you know power was lost.

This is what happened. Not really sure why it faulted, but I happened to look at the inverter and saw the light was red, not green. Shut it off, started it, worked fine, but not interested in having it fail while I'm sleeping and the whole fridge/freezer spoils.

I got at best 350W peak out of the panels on a singular good day, and with crummy days, solar definitely wasn't keeping up. Pretty slow discharge as it was maybe 0 loss for the daytime, but you've got to account for night. Why I think maybe 800W would be the minimum. It's so dark in winter though, I question if even that would be enough.

I noticed ~500w consumption at times, probably freezer cycling? Not sure, as when I normally checked and the fridge was running, it was maybe 150W. It didn't seem to be the compressor coming on, as when I caught it, it didn't seem to really ramp down, but I didn't have a way of checking its history to see if that was a constant occurrence. Of course the inverter efficiency comes into play, so it's not 150-500W for the fridge itself, but that doesn't matter, that's what the battery is feeding.

Done with that experiment. Without going whole hog with significant storage and panels, I don't think just a battery and inverter with small solar array is practical for a home appliance like the fridge. It could work pretty easily in an RV/trailer where the whole roof could be panelled and most everything will run off 12V, but without a transfer panel or whatever they are called to run dedicated circuits off of, it's a mess of wires everywhere in a house.

 

[imiceman44]

I ran the fridge for about three days. It is a 2000w true sine wave inverter, at least according to the specs and tests done on YouTube.

One thing I hadn't considered is what if the inverter faults? With your home electric you know if power goes out if you are home. Even if it comes back on microwave clock will be flashing etc., so at least you know power was lost.

This is what happened. Not really sure why it faulted, but I happened to look at the inverter and saw the light was red, not green. Shut it off, started it, worked fine, but not interested in having it fail while I'm sleeping and the whole fridge/freezer spoils.

I got at best 350W peak out of the panels on a singular good day, and with crummy days, solar definitely wasn't keeping up. Pretty slow discharge as it was maybe 0 loss for the daytime, but you've got to account for night. Why I think maybe 800W would be the minimum. It's so dark in winter though, I question if even that would be enough.

I noticed ~500w consumption at times, probably freezer cycling? Not sure, as when I normally checked and the fridge was running, it was maybe 150W. It didn't seem to be the compressor coming on, as when I caught it, it didn't seem to really ramp down, but I didn't have a way of checking its history to see if that was a constant occurrence. Of course the inverter efficiency comes into play, so it's not 150-500W for the fridge itself, but that doesn't matter, that's what the battery is feeding.

Done with that experiment. Without going whole hog with significant storage and panels, I don't think just a battery and inverter with small solar array is practical for a home appliance like the fridge. It could work pretty easily in an RV/trailer where the whole roof could be panelled and most everything will run off 12V, but without a transfer panel or whatever they are called to run dedicated circuits off of, it's a mess of wires everywhere in a house.

I am working on a sub panel that will be necessities kind of, water heater, fridge, some lights, and chargers for phones and computers.
My plan is to put it on an automatic switch where the solar is primary so I am constantly using it and saving money on electricity and testing while I have a backup, the power company.

 

[Blue85]

It may have been running a defrost cycle. I don't know how much that draws, but it's electric heat strips in the freezer. If you were in a pinch and needing to use the inverter, you could unplug the element for that duration. AFAIK it will catch up later, but during a power outage you probably won't open the door much anyway. Maybe the compressor kicking on while the defrost is running puts it over the limit. It could also mean the battery voltage got low. Some inverters are super fussy about input voltage.