Off Grid 10kW Solar System - Sizing The Battery Bank

Off Grid 10kW Solar System – Sizing The Battery Bank

Our off grid solar system is ready to go online. This video shows how we sized our battery bank to meet our needs. We used the Rolls s-1450 batteries for our system.

Here is the formula to calculate the proper size for the system. Our goal was to not notice a huge difference in available power when the house is built. We wanted to not have to always worry about power.

This formula is based on using 28kW a day. (We use about 21kW to 24kW)

Load requirement:
28kW per day (about 840kW per month)
DC input voltage = 48v
28000 / 48 = 583 amp h/day
583 * 1.25 (for inverter loss and battery efficiency) = 728 AH/day

Battery sizing:
728 amp hr/day * 1 day of autonomy = 1456 amp hr
1456/0.8 (battery discharge) = 1820 amp hr
1820*1.59 lead acid battery temperature multiplier = 2894 optimum battery size in amp/hours
2894/1124 amp/hours (for the S-1450s) = 2.6
2 (number of parallel strings required)* 24 (2v*24=48v)= 48 x S-1450

Here is a link to the batteries: http://www.rollsbattery.com/wp-content/uploads/batteries/S-1450.pdf

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