To determine the suitable capacity of a lithium battery for a two 225-watt solar panel, you need to consider several factors, including the desired backup time and the average daily energy consumption.
Average Daily Energy Production: For two 225-watt solar panels, the total capacity is 225 watts + 225 watts = 450 watts. Assuming an average of 5 hours of full sun per day, the daily energy production would be:
Daily Energy Production = 450 watts (total solar panel capacity) x 5 hours ≈ 2250 watt-hours or 2.25 kilowatt-hours (kWh).
Desired Backup Time: Determine how many days of backup power you want the lithium battery to provide. Let's assume you want the battery to support your energy needs for one day without solar input (e.g., during cloudy days or at night). The desired backup capacity is 2.25 kWh.
Battery Efficiency and Depth of Discharge: Consider a battery efficiency of 90% (0.9) and a depth of discharge of 80% (0.8):
Suitable Battery Capacity = Desired Backup Capacity / (Battery Efficiency x Depth of Discharge)
Suitable Battery Capacity = 2.25 kWh / (0.9 x 0.8) ≈ 3.13 kWh.
In this example, a lithium battery with a capacity of approximately 3.13 kilowatt-hours (kWh) would be suitable for two 225-watt solar panels if you want one day of backup power.
As always, these are rough estimates, and the actual requirements may vary based on your specific energy consumption patterns and location. To get a more accurate assessment, it's advisable to consult with a solar energy system installer or an expert who can design a solution tailored to your individual needs.