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445 sats \ 8 comments \ @Solomonsatoshi 7 Mar tech

I live most of the time offgrid on a block of land outside the city.

It was a priority to set up a basic system of electric supply enough to power a fridge freezer, lights, electric jug, toaster and internet plus power tools up to circular saw. No power bills.

The system started with 2x 300 watt solar panels and a 100ah 24v lead acid deep cycle battery feeding a 2500 watt inverter. This basic system cost around NZD$2200.

Have since added two more 300w solar panels and 2x 100ah Lifepo4 batteries and a 3500 w inverter. This second system cost about NZD$3500- mostly the batteries at NZD$1100 each.

So now have two independent solar power systems each with its own batteries and inverter. The most essential requirement of the system is to keep the fridge freezer running all year- if it is cloudy for a week you still want the fridge freezer working. Do have a small old and noisy 2 stroke 800watt petrol back up generator but it is not something you want to have to use often.

So the 2x 300 watt PVs with the 100 watt lead acid deep cycle battery were enough to power the fridge freezer most of the time- only occasionally needing to use the petrol generator. With the new additional 2 x 300watt PVs and 2x 100ah/24v Lifepo4 batteries I have not yet ever had to use the petrol generator and expect it is unlikely unless there is a nuclear winter style event!

The second Lifepo4 100ah was more to try to enable more bItcoin mining but even with that extra capacity it is hard to run more than 2TB/sec on Nano3 and in winter I think it will be back down to running my Lucky Miner at 700 GH/s. Maybe need more PV panels but at some point you must draw the line of cost benefit. The fridge freezer is the crucial load factor as you cannot turn it off and it requires power 24/7 so buying an efficient one that only uses about 280 kw/year makes the system overall more viable.

Am still not sure I trust the Lifepo4 batteries as they are high tech and full of complex circuitry but they do hold charge much longer than lead acid and they supposedly last much longer- claims of up to 20 years- will believe when it is an observed fact rather than claim by merchants selling them.

Good quality deep cycle lead acid batteries are still a viable choice and their simplicity make them feel more reliable - I still use them on the original system for heavy demand power applications in the workshop like running circular saw. where you might be drawing up to ~ 2400watts ~ 100amp at 24 volts. But because the Lifepo4 have much better holding capacity of power they now supply the fridge freezer and most other small household appliances.

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21 sats \ 1 reply \ @itsrealfake 7 Mar

I have a buddy who builds his own LiFePO4 batteries from stock components, and then connects them with management circuits, and if you're doing that... you're pretty close to bare metal (like with the deep cycle lead acid). it's still expensive to do that, but I would recommend it's a good thing to know how to do.

Sweet setup. Similar to mine, but I'm not running a fridge.

20 sats \ 0 replies \ @Solomonsatoshi OP 8 Mar

Yes looked at that but wasn't confident I could get it right technically - but definitely would be a great thing to learn how to do. When you buy a prepackaged Lifepo4 battery pack it's difficult to know how well its been assembled so important to try to discover how reliable the merchant is.

21 sats \ 3 replies \ @User21000000 7 Mar

How big a block have you got? Are you running any animals like sheep or cows at all?

Did you build your house? Very cool

0 sats \ 2 replies \ @Solomonsatoshi OP 8 Mar

Just over 20 acres but its not great soil- stony and harsh climate and strong winds- it was a forest block before but the trees got blown down before they could be harvested. Yes built cabin from some of the wood I salvaged and chainsaw milled from the windblown forest...the rest got sold mostly for making pulp for making paper. Neighbouring farmer has been grazing his sheep on most of the block but I am planning to get my own stock in the next year or two. Planning on a few pigs (Kunekune which can survive on grass) and maybe a few cattle and sheep. Have been planting trees to see what grows and get some shelter...the winds can be brutal.

14 sats \ 1 reply \ @User21000000 8 Mar

Do you get snow there as well or just big winds

0 sats \ 0 replies \ @Solomonsatoshi OP 8 Mar

Most years it snows a few times but doesn't stay on the ground more than a few days...but there is snow on the Southern Alps 10-15 miles to the west all winter and the cold air flows down from that snow most of the winter and into late spring when it melts. The worst wind is the Norwester in summer and is hot and dry.

21 sats \ 1 reply \ @Signal312 7 Mar

Thanks for the interesting write-up! Looks like you have a pretty large freezer. How big are the solar panels, and how much sun exposure do you get?

Would you like to share any info about costs?

68 sats \ 0 replies \ @Solomonsatoshi OP 8 Mar

From memory lifepo4 100ah/24v batteries were about NZD$1100 each...they can cost more or less depending on quality. Pair of 100ah 12volt deep cycle lead acid batteries to make a 24volt system were about NZD$600. 300watt PVs were only NZD$200 each but that was about 2021. Inverters were ~NZD$250 for the 2500watt and about ~NZD$400 for the 3500watt...again price probably gone up since these were bought around 2022-23. For cable I used mostly TPS cable from metal salvage yard- they sometimes have new cable but its sold at scrap metal price.

The sun in summer is plenty with a southern hemisphere latitude about 44 degrees but in winter the energy from solar I estimate to be only about 1/3 that of summer- so that is when the batteries and the whole set up are tested...fortunately with the fridge freezer located in the shipping container it also works less hard in winter with the temperature in the container sometimes colder than the fridge!

I have one set of panels tilted slightly to face the winter sun better and making them adjustable would be worthwhile - if I get around to it...as the mid winter sun gets pretty low and weak. The freezer is about 100 litres and the fridge (top part) is about 220 litres. It's a very efficient unit and cost about NZD$700.