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Battery Size Formula:
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The battery size calculation determines the required battery capacity (in amp-hours) to store energy from solar panels based on power output, duration of use, and battery voltage. It's essential for designing efficient solar power systems.
The calculator uses the following equation:
Where:
Explanation: The equation converts watt-hours of energy needed into amp-hours based on the system voltage, accounting for the fundamental relationship between power, voltage, and current.
Details: Proper battery sizing ensures your solar system can meet energy demands during periods without sunlight, prevents battery damage from over-discharge, and optimizes system cost and performance.
Tips: Enter solar panel output in watts, hours of operation needed, and battery bank voltage. All values must be positive numbers. For lead-acid batteries, multiply result by 1.2-2.0 for proper depth of discharge.
Q1: What's the difference between Ah and Wh?
A: Amp-hours (Ah) measure charge capacity, while watt-hours (Wh) measure energy capacity. Wh = Ah × V. This calculator converts between them.
Q2: How does battery type affect the calculation?
A: Different battery chemistries (lead-acid, lithium) have different depth-of-discharge limits. The calculation gives theoretical capacity - apply appropriate safety margins.
Q3: Should I account for system inefficiencies?
A: Yes, typical solar systems have 70-85% efficiency. Multiply your result by 1.15-1.4 for realistic sizing.
Q4: What about days of autonomy?
A: For multiple days without sun, multiply the "hours" by the number of days needed.
Q5: How does temperature affect battery capacity?
A: Cold temperatures reduce battery capacity. In cold climates, size batteries 20-30% larger than calculated.