48V Cabin System

[Blumbergh]

Good afternoon all,

I have a smallish cabin in Missouri 640 sqft, it is hot here and the humidity sucks to say the least in the summer. In the winter we can get to negative temps. I run a wood stove for heat so I am good and warm for the deer season and beyond. The cabin is very well insulated from the outside as long as you keep it closed up. I built the cabin to be as efficient as possible. Propane for the stove and tank less water heater. All of my lights are 9w LED x10 (4 -8 hours a day max) but they are never all on at the same time (unless the kids are there). My water pump pulls about 1200w when on and maybe runs a total of 45 mins a day max, the stove hood fan is 40w when on high (maybe an hour a day) the ceiling fans are AC to DC so they pull 39w each when on high x3, 4 -8 hours a day max. I have an exhaust fan in the bathroom which pulls 38w, one hour a day max. A Keurig for a morning cup of Joe and if the kids are there I end up with what seems like 6 or 8 apple devices charging for whatever reason, maybe 3 hours a day on each of those.

Now here is the kicker, I have a full septic, water catchment and filtering system, full bath and kitchen all to make life nice and homey and keep the wife happy, but she will not go stay with me in the summer because it is just too hot, and I tend to agree.

So I would like to install a Mini Split AC unit and be able to run it off of Solar during the day and battery at night an AC unit will not run all the time but I am estimating about 900W on average about 12 hours a day.

Now I’ll say I understand very little about how much battery I’ll need to power this and have a day in reserve. For some reason I just can’t get that part through my head. What I had in mind so far is the following:

2 x mpp solar LV 5048 5kwh all in one systems

https://www.mppsolar.com/v3/split-phase-lv-series/

2 x Big Battery 48v LiFePO4 power walls (5kWh 104AH) each running in parallel 5kWh, 208 AH.

https://bigbattery.com/product/48v-lifepo4-powerwall/

20 x Trina solar 400w mono solar panels (8000w total)

https://www.ecodirect.com/Trina-Solar-400-Watt-Mono-Solar-Panel-p/trina-tsm-400-de15h.htm

So my question for whomever is:
1. Will this system do what I am asking it to do? or am i way off?
2. Will the LV 5048’s handle half of the panels coming into them, 10 to each? or am i way off?

Sorry this is so long, I just wanted to try to answer all of the questions I could think of you all asking up front.

Am I just dreaming here folks or am I going to need like 10x the battery storage to make this happen?



Thank you,

 

[MisterSandals]

Can you come up with a daily usage in watt hours? You have a lot going on.
And your estimate for a split mini of 900w for 12 hours should take into consideration the cooling cycle length if not 100%.
Running this for 12 hours will be a big number so any accuracy in estimating that will get you closer to your system requirements.
Sounds like you are in the ballpark if i were to guess.

 

[Blumbergh]

understood. I'm estimating 12hours because the thing could be running up to 12 hours a day on a hot weekend with the unit cycling on and off.
the rest of it im looking at about 13500w per day with a total peak load of 3372. that AC unit is really killing me.

 

[MisterSandals]

that AC unit is really killing me.

Yea, thats a common thing.

It beats the heat killing you, either directly or acting thru the hands of your wife.

 

[schmism]

I think you have overspec your inverter need and have under spec your battery.

I think you could do 2x 3000w 48v Growatts in parallel single phase. And for the same $1600 buy into the 280ah group buy cells on the forum. That would give you 560ah which would be more in line with makeing it through the night if you had to run the AC.

 

[Blumbergh]

Ok so let’s recap if I went with the same number of panels (20) dropped down to 2, 3000w all in one inverters. Then 2 higher ah batteries that should do the trick.

if I wanted to go up to 4 batteries for 1120ah would the system be able to recover in a day based on what is there from a panel perspective. At this point I am only able to go up to 24 panels total based on the roof space I have available.

 

[MisterSandals]

13500w per day

13500wh / (24 x 400w) = 1.4h to recharge (assuming 100% efficiency)

1120ah x 48v = 53,760wh storage. Looks to be about 4 days of storage at your stated rate.

Full recharge cycle:
53,760wh / (24 x 400w) = 5.6h

 

[Blumbergh]

13500wh / (24 x 400w) = 1.4h to recharge (assuming 100% efficiency)

1120ah x 48v = 53,760wh storage. Looks to be about 4 days of storage at your stated rate.

Full recharge cycle:
53,760wh / (24 x 400w) = 5.6h

Ok well I can dig on that. Even if I have to build it in pieces. All in on the panels then add the inverters and batteries to support the full load. Honestly this whole aspect would be a great solution and I would be able to utilize my place with the family so much more.