The depth of discharge (DoD?) and estimated/"promised" cycles of various batteries is a bit confusing to me, including the 12/24/48v to inverter conversion of amp hours when sizing a system.
For example, https://www.altestore.com/blog/2017/02/simpliphi-lithium-batteries/
shows 10,000 cycles at 80% DoD (with "that's 27 years!" next to it). So I read that to mean I can use up to 20% of the available power on a given night or cloudy day, and the next sunny day when it recharges to full, I have used up one of those cycles? I see other batteries like https://www.wholesalesolar.com/1898601/fullriver/battery-banks/fullriver-agm-415-ah-48-vdc-19-920-wh-8-battery-bank
which promise "hundreds" of deep cycles and a 7 year warranty.
The property I bought is at 48 degrees latitude, and averages 1.2 sun hours a day around the winter solstice. Tying into the grid will start at $25,000 plus permits and monthly bills, so I'm not going down that road if I can avoid it! But I will need to plan a system size for having a cloudy winter week. I am buying a kill-a-watt to see what my current power use is, and have a chest freezer that will be converted to fridge temps to save some power. I currently average 3kwh a day when the window AC is off (12/23/17 it was 12kwh, as it was 102 degrees F that day! It was 95F on Christmas day, I miss regular seasons of the midwest USA!).
So let's say 3kwh per day is the norm in the future even though I doubt I will have a big screen TV and inefficient fridge in a Wofati/Oehler-planned home, but I will have a well pump for example. The assumed 30% conversion losses are added in to say I would need 3900 watt-hours of generation. Hopefully panels that can still partially charge on cloudy days can save me, since some solar calculators say I need 13 panels at 300 watts each for those 1.2 sun hours...
So here's the battery portion that has been a bit confusing to me in the past
: the battery linked above offers 415AH at 48v which becomes (A*V=W) 19,920 watt hours? On a cloudy winter day, using panels which still generate a charge, I'm getting that 1.2 sun hours on average over the 10 hours that the sun is out(barring obstructions like trees or 3 feet of snow drift)? If that battery should not be drained below 80% of capacity to extend it's lifespan, then that's about 4000 watt hours in a given day, and I'm at 3900 watt hours of generation including system loss. So I need to have enough panels to charge that 3900/4000 watt hours back each day, say 13 panels at 300 watts each? This is what is getting me confused, as some folks on here talk about having 440AH, 24v off grid systems with no backup generator in northern areas with cloudy winter days and they have 1000 watts in panels or less.
Is 3kwh of consumption the issue here? I expect the converted chest freezer will lower my power use, and downsizing the space with fewer gadgets like the TV will help as well. I typically use 1-2 LED lights @ 12watts/120v, the fridge, and my laptop regularly. The latter will likely be just a tablet down the road, or Linux-converted Chromebook for something a little more secure. Finally a cell phone that's kept charging as I would tether it for WiFi internet access. Converted chest fridges typically take less than 0.25kwh a day, so unless I add in a toaster oven to compensate for poor iron skillet/rocket stove cooking, I would expect my electrical use would be about as low as it can be without giving up all electronics. So the size of system recommended seems massive, despite it being in a northern climate.
Am I missing something obvious?
Edit: and is there a time when wiring the panels and batteries as 12v is better than 24v or 48v? Isn't there less line loss at higher voltage, and smaller gage wires can be used? I don't expect a long run with a house-mount being possible, maybe 30-50 feet to reach the batteries inside.