Enter your load requirements and desired backup time to calculate needed battery capacity. Battery Capacity (Ah) = (Load Watts × Backup Hours) / (Voltage × DoD/100) This formula has been verified by certified solar engineers and complies with industry standards. Get accurate specifications for 18650, 21700 cells with series. . Usable capacity differs from total capacity: Lithium batteries provide 90-95% usable capacity while lead-acid only offers 50%. Factor in 10-15% efficiency losses and plan for 20% capacity degradation over 10 years when sizing your system. Power and energy requirements are different: Your battery. . Battery capacity and backup-time sizing for solar, UPS, and stationary storage systems is based on load profiles, autonomy requirements, depth of discharge, round-trip efficiency, temperature effects, and allowable C-rates.
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