1. What is the Battery Size Calculation?

The battery size calculation determines the appropriate battery capacity (in kWh) needed to store energy generated by solar panels, accounting for daily sunlight hours and desired depth of discharge (DoD).

2. How Does the Calculator Work?

The calculator uses the following equation:

Where:

• \( \text{Panel Capacity} \) — Rated capacity of solar panel system in kilowatts (kW)
• \( \text{Daily Sun} \) — Average daily sunlight hours at your location
• \( \text{DoD} \) — Depth of Discharge (decimal from 0 to 1, typically 0.5 for lead-acid or 0.8 for lithium)

Explanation: The equation calculates the energy production (kWh) and divides by the DoD to account for not fully discharging the battery.

3. Importance of Proper Battery Sizing

Details: Correct battery sizing ensures you have enough stored energy for periods without sunlight while avoiding overspending on unnecessary battery capacity.

4. Using the Calculator

Tips: Enter panel capacity in kW, average daily sun hours, and your desired depth of discharge (0.5 for 50% DoD). All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is Depth of Discharge (DoD)?
A: DoD is the percentage of battery capacity that can be used (e.g., 0.8 means you can use 80% of the battery's capacity).

Q2: How do I estimate daily sun hours?
A: Check solar insolation maps for your location or use historical weather data (typically 3-6 hours depending on location).

Q3: What's the difference between lead-acid and lithium DoD?
A: Lead-acid batteries typically use 50% DoD (0.5) for longevity, while lithium can often use 80% DoD (0.8).

Q4: Should I add a safety margin?
A: Yes, consider multiplying the result by 1.2-1.3 to account for system inefficiencies and unexpected usage.

Q5: How does this relate to days of autonomy?
A: For multiple days of backup, multiply the result by your desired days of autonomy (e.g., 2 days = 2× the calculated size).