Coydon
New Member
I'm looking to build my second solar station iteration. I currently have a 12V FLA 225Ah system connected to a single 350W panel by way of a 30A MPPT charger controller. It has been plenty for my basic startup needs, although I am looking to add some refrigeration to my campstead this year. I'd like to go larger and give LFP a try, keeping the older system as a backup/second location option. As I build a more permanent structure, I will not be moving toward a conventional "grid-style" power system, but will continue to use various 12V appliances with a chest freezer on an inverter, with other 120 devices only occasionally.
I found some used panels at a good price. I picked up 6 Sunpower "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 the shed and the spot I have planned for it would not support more than 6, I'd have to relocate and run much longer wires.
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 for my instance. I'm picking 1.5kWh/day demand and 3 days reserve along with 2 hours of daily solar insolation in my northern clime as arbitrary points to move forward with. This will be much greater most of the year but anticipating our short, cloudy fall and winter days (including a 60* mounting angle for the panels). Keeping a healthy battery bank is more important than having a suplus of energy stored at any given time.
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/changes in the future.
I currently have an EPEver Tracer 3215BN 30A charger, but it only does 12/24V systems. I was ready to move to a 48V system. 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. If I run the panels in 2 strings of 3, it would be 18A @ 130V (Sunpower mono panels w/Max Voc of 64.9, Max A 5.98). Is that a good idea? Will the EPEver Tracer (max W 780) manage over-paneling?
What other calculations/considerations am I missing? I'm not clear on the whole C calculation thing yet, trying to digest everything in small bites. It seems to me the 1.5kWh input per day would replace my fallback draw amount, but is that enough to keep the LFP bank happy?
I found some used panels at a good price. I picked up 6 Sunpower "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 the shed and the spot I have planned for it would not support more than 6, I'd have to relocate and run much longer wires.
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 for my instance. I'm picking 1.5kWh/day demand and 3 days reserve along with 2 hours of daily solar insolation in my northern clime as arbitrary points to move forward with. This will be much greater most of the year but anticipating our short, cloudy fall and winter days (including a 60* mounting angle for the panels). Keeping a healthy battery bank is more important than having a suplus of energy stored at any given time.
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/changes in the future.
I currently have an EPEver Tracer 3215BN 30A charger, but it only does 12/24V systems. I was ready to move to a 48V system. 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. If I run the panels in 2 strings of 3, it would be 18A @ 130V (Sunpower mono panels w/Max Voc of 64.9, Max A 5.98). Is that a good idea? Will the EPEver Tracer (max W 780) manage over-paneling?
What other calculations/considerations am I missing? I'm not clear on the whole C calculation thing yet, trying to digest everything in small bites. It seems to me the 1.5kWh input per day would replace my fallback draw amount, but is that enough to keep the LFP bank happy?
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