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Battery Capacity Formula:
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The battery capacity calculation determines the required amp-hour (Ah) capacity for a 12V solar battery bank based on your daily energy needs and desired depth of discharge. This helps ensure your solar system can meet your power requirements.
The calculator uses the following equation:
Where:
Explanation: The equation converts your energy needs from watt-hours to amp-hours at 12V, then accounts for how much of the battery's capacity you plan to use regularly.
Details: Correct battery sizing is crucial for solar systems to ensure reliable power availability, prevent over-discharge (which shortens battery life), and optimize system cost.
Tips: Enter your total daily energy consumption in watt-hours and your desired depth of discharge (typically 0.5 for lead-acid batteries). The calculator will determine the required battery capacity in amp-hours.
Q1: What is a typical depth of discharge for solar batteries?
A: For lead-acid batteries, 50% (0.5) is common. Lithium batteries can often handle 80-90% (0.8-0.9).
Q2: How do I determine my daily energy needs?
A: Multiply each appliance's wattage by hours used per day, then sum all values. Energy monitors can provide accurate measurements.
Q3: Should I add extra capacity?
A: It's recommended to add 20-25% extra capacity to account for inefficiencies and unexpected loads.
Q4: What about days without sun?
A: For autonomy days (no sun), multiply your daily needs by the number of days you want coverage, then calculate capacity.
Q5: Does temperature affect battery capacity?
A: Yes, cold temperatures reduce available capacity. In cold climates, you may need to increase capacity by 20-30%.