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Question on small off grid cabin solar setup

DyslexicDancer

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I'm in the process of building a small 300 sq/ft off grid cabin in Texas and had a question for you guys on going full DC vs going AC/DC

My situation is that I have already purchased 24 CATL 302AH batteries for this project and approximately 4kw of used solar panels I purchased off Craigslist. and I'm not sure which direction I should go with the the solar power system

The original plan was to assemble the battery into a 8S3P 24V 24Kwh battery and power everything off DC. That means buying a more expensive DC refrigerator and a more expensive 24V DC 9000 BTU Mini Split Heat Pump. I can get a 24V R134A Mini Split from China for about $1500 , for a Fridge/Freezer I was planning on buying a 24V R134A Compressor from China to modify a used Fridge I already have. Changing out the compressor and re-charging the unit shouldn't be too much of a problem, but there is the extra cost of the new DC compressor to consider. Lighting will be 24V LED, they are not really a factor in my decision as they are pretty inexpensive. If I go this route I'll also need to purchase charge controllers for the system. I was looking at using two 100amp EPEVER charge Controllers ($900) or possibly two 100 Amp Victron charge Controllers ($1600)

I have been thinking lately that it might be better to assemble the battery into a 16S1P 48V 16Kwh battery paired with a growatt 3000TL inverter. I have the SPF3000TL inverter already, so there's no additional cost for the Inverter if I go this route. This simplifies the system as I can use the Growatt Inverter for charging the battery and for powering the fridge I already have , I can purchase a Pioneer 110V 9000BTU Mini Split for a lot less than the 48V DC Mini Split from China and I have more faith in the Pioneer Mini Split than an Unknown quality 48V Mini Split that I've found on Alibaba. For lighting I'd use a DC/DC converter to power the 24V DC lighting

What do you guys think? Is it better to lower the battery capacity to 16KW and go with a 16S1P 48V battery, the Growatt Inverter/Charger, and AC Appliances, or is it better to keep everything DC and go with a bigger 8S3P 24Kwh 24V battery?

Also I currently plan to use an Overkill BMS, but wanted to know if you guys think the JK BMS would be a better choice since it has 2A of active balancing and 200Amps of output?

Thanks in advance for the advise, I appreciate it
 
Just a thought. Instead of losing the battery capacity you could go with both a 24vdc and a 48vdc setup. 16 cells for 48vdc leaves 8 for 24vdc.
Simply divide up what you want to power and how much solar panels you dedicate to each battery bank.
 
I'm with @jtvt When I did my trailer, I went all-in-one MPP Solar 3048LV and did AC. I did a120vac -> 12vdc @ 80a converter for a few things the trailer needed at 12vdc such as the water pump and the powered tongue jack but othewise all is 120v including the refrigerator and toaster (mentioned above) etc etc.

I'm aware there are enthusiasts for 12v - and there is some loss form DC -> AC -> load conversions but that's really an issue of charging rather than consumption. You might have to charge 10% more to get the same consumption out. But since I want all-in-one anyway - why not use it's AC output.

I don't think there's any right answer here :)
 
I wouldn't bother with DC. Everything is just so much simpler with AC. Like for example if you want to use a toaster in the future.
Very true, I have thought a Microwave might be in the future for the cabin,. I appreciate the comment
 
Just a thought. Instead of losing the battery capacity you could go with both a 24vdc and a 48vdc setup. 16 cells for 48vdc leaves 8 for 24vdc.
Simply divide up what you want to power and how much solar panels you dedicate to each battery bank.
That's a very good Idea. I was thinking if I go with the 48V system I'd just keep 8 batteries in storage for any potential bad cells in the future, but it makes more sense to use them for a 24V system for all the DC loads
 
Being without AC would be a issue for me. Too many things that might come up needing AC. 24v Growatt is an option if you really need those 8 odd cells. You would of course have to buy the 24v AIO. Or buy 8 more cells to have 2p16s.
 
Being without AC would be a issue for me. Too many things that might come up needing AC. 24v Growatt is an option if you really need those 8 odd cells. You would of course have to buy the 24v AIO. Or buy 8 more cells to have 2p16s.

Yeah that's how I see the question. DC just would not be one of the options. It's "do I buy a 24v inverter and use all the cells, or use the 48v inverter that I already have with only 16 cells". My answer would be use the 48v inverter and save up for another 8 cells.
 
Yeah that's how I see the question. DC just would not be one of the options. It's "do I buy a 24v inverter and use all the cells, or use the 48v inverter that I already have with only 16 cells". My answer would be use the 48v inverter and save up for another 8 cells.
I have a fairly large 24v system (2, 3000w Growatts) and I wish I had went 48v.
 
Yeah that's how I see the question. DC just would not be one of the options. It's "do I buy a 24v inverter and use all the cells, or use the 48v inverter that I already have with only 16 cells". My answer would be use the 48v inverter and save up for another 8 cells.
I don't think going the 24V route with a 24V inverter would work for me, I already have a 48V Growatt I can use, and the 24V Growatt only supports 2KW of solar panels, so I'd need 2 of them, but I agree that DC only will probably not be the route I take, even though DC only was my original plan I've been thinking that going 48V with the inverter will just be easier and better for the cabin. I guess the question is buy 8 more batteries for a 32kwh 48V battery or build a 16kwh 48V battery for the 120V AC loads and an 8kwh 24V battery for the DC loads
 
I have a fairly large 24v system (2, 3000w Growatts) and I wish I had went 48v.
I appreciate the comment, I'm pretty set on 48V and I already have the 48V inverter. I have had a few people tell me in person to keep everything DC and do away with the inverter losses and wanted to know if going DC only made more sense.

What about your 24V system has you wishing you went 48V instead?
 
I appreciate the comment, I'm pretty set on 48V and I already have the 48V inverter. I have had a few people tell me in person to keep everything DC and do away with the inverter losses and wanted to know if going DC only made more sense.

What about your 24V system has you wishing you went 48V instead?
I have my eye on some of the newer AIO units and they are 48v. That is the real reason. The type that don't require a battery, have a completely different internal design which leads itself to using the solar PV energy first.
 
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