I'm looking to build my second
solar station iteration. I'm looking at all of the
online guidance for building a system and they, being mostly geared toward people with a deathgrip on late 20th century
energy usage habits, are often more confuzing than helpful for someone looking to optimize their use of electrical appliances in line with appropriate tech thinking. Hoping some
permie brains here are willing to help think outside the boxgrid.
I currently have a 12V FLA (Flooded Lead Acid) 225Ah system connected to a single 350W panel by way of a 30A MPPT (the better kind) charger controller. It has been plenty for my basic startup needs, although when I tried to do Starlink last fall the router would run down the batteries below 50% if left on over night. Also I'm using a car cooler for refrigeration and the 'cigarette' lighter connection is outside the protection offered by the charge controller. I've left it plugged in by mistake a few times and run the batteries down to 0. The FLA has been surprisingly resilient to abuse, but is just over a year old so time will tell. I'd like to go larger and give LFP (Lithium Iron Phosphate) a try, keeping the older system as a backup/second location option.
To start I found some used panels at a good price. I picked up 6 "327W" panels, the seller said they were 3-5 years old and
should be working above 95% at least, I believe. It wouldn't be too difficult to pick up more if needed, but mounting 6 panels with little infrastructure is already proving to be a task.
Looking at likely appliances, I'm guessing my daily power demand would be around 1-1.5kWh. I have no set habits and will adjust as needed, so the primary concern is to find a 'sweet spot' in available materials to move forward with. Refrigeration is the primary anticipated need, but given the fact that days with greater need for power will coincide with higher
solar input, the usual warnings I see about 'buffer' calculations seem overly alarmist. I'm picking 1.5kWh/day and 3 days reserve along with 2 hours of daily
solar insolation as arbitrary points to move forward with.
Given lead times on LFP battery orders, I'd like to place an order for some soon. Seems to me a DIY bank with prismatic cells would be worth it to save a bit of money over prefabricated rack systems. I would like to have a reliable system and just focus on other things, but this is essentially paying myself to learn more about solar charging and know how to handle problems/expansions in the future.
I have a pretty good EPEver 30A MPPT charger, but it only does 12/24V systems. I was thinking a 48V system would be the next step up from the 12V to allow for affordable cables to cover moderate distances. However, I'm also calculating that the battery bank should be about 5kWh total. Pricing out prismatic cells, 16 100A cells would cost around $1000 and require a new charger purchase to use with the 48V system. OTOH, 8 300A cells would cost about the same, store 50% more power, and allow the use of my current charge controller as a 24V system. I think. I've gone in circles so many times trying to follow instructions coming from the 'consumer first' camp, I haven't grokked the charge rate info. Hopefully my brain fog will be gone long
enough to work that out soon, or someone here has followed all that an can fill in the blanks...?
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