I have one 60-cell 260Wc ~30V ~8.5A panel left over after a solar installation.
I did record consistent and factual 1400Wh per day and per panel in winter.
I want to use the energy of this extra panel for a home-made low-voltage ventilation in our house (12V ideally, or 24V more realistically(?)).
- In winter I can use the "real time" production and use any surplus to heat the vented air itself.
- But in summer, I would like to draw the maximum of daily-stored energy to vent the house with cool air during the night.
I have no need for cycles larger than 24h... but I still need a battery.
So here is the question: I want to store the best of a 1400Wh daily solar production into a battery. Which capacity should I get?
As you see I am not driven by my power requirement, but by what I can already produce with this panel. It stands out from what is usually talked about and what solar calculators do (namely: assessing needs to know the hardware to buy).
Given "rules of thumbs" like "15 watts delivers about 3,600 coulombs per hour of direct sunlight (i.e. 1 Ah)":
1400Wh in a 12V battery = 116Ah 1400Wh in a 24V battery = 60Ah
I was to get a 60Ah, 24V battery setup (e.g. 8 LiFePo cells) but I realized I am probably oversizing it given losses in the changer, BMS (battery management system) and battery charging chemistry itself?
I am unsure that the above "rule of thumb" takes these issues into account. Can someone help me?