Solar Battery Calculator

Battery Capacity Formula:

\[ \text{Battery Capacity (Ah)} = \frac{\text{Solar Energy Production (Wh)} \times \text{Autonomy Days}}{\text{Battery Voltage (V)} \times \text{Depth of Discharge}} \]

Solar Energy Production:

watt-hours

Autonomy Days:

days

Battery Voltage:

volts

Depth of Discharge:

decimal (0-1)

Battery Capacity:

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1. What is Battery Capacity Calculation?

The battery capacity calculation determines the required battery size (in amp-hours) for a solar power system based on your energy needs, desired autonomy days, battery voltage, and acceptable depth of discharge.

2. How Does the Calculator Work?

The calculator uses the battery capacity formula:

\[ \text{Battery Capacity (Ah)} = \frac{\text{Solar Energy Production (Wh)} \times \text{Autonomy Days}}{\text{Battery Voltage (V)} \times \text{Depth of Discharge}} \]

Where:

Solar Energy Production — Your daily energy consumption in watt-hours
Autonomy Days — Number of days you want the system to run without sun
Battery Voltage — Voltage of your battery bank (typically 12V, 24V, or 48V)
Depth of Discharge — Fraction of battery capacity you can safely use (typically 0.5-0.8)

Explanation: The formula calculates how many amp-hours your battery bank needs to store to meet your energy requirements for the specified number of days, accounting for how deeply you can discharge the batteries.

3. Importance of Proper Battery Sizing

Details: Correct battery sizing ensures your solar system can meet your power needs during periods of low sunlight while maximizing battery life by not over-discharging.

4. Using the Calculator

Tips: Enter your daily energy production/consumption in watt-hours, desired autonomy days (typically 2-5), battery bank voltage, and depth of discharge (0.5 for 50% recommended for lead-acid, 0.8 for lithium). All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What's a typical depth of discharge for different batteries?
A: Lead-acid: 50%, AGM: 70-80%, Lithium-ion: 80-90%. Deeper discharge reduces battery lifespan.

Q2: How do I calculate my daily energy needs?
A: Sum the watt-hours of all devices you'll power (watts × hours used per day).

Q3: What's a reasonable number of autonomy days?
A: 2-5 days is typical. More days require larger batteries but provide more backup.

Q4: Should I oversize my battery bank?
A: 10-20% extra capacity is recommended to account for battery aging and unexpected loads.

Q5: How does temperature affect battery capacity?
A: Cold temperatures reduce available capacity. In cold climates, you may need 20-30% more capacity.