Introduction
One of the most common mistakes in home solar installations is incorrect battery bank sizing. A poorly designed battery system leads to frequent deep discharge, reduced efficiency, and early battery replacement.
This guide explains how to correctly size a lead-acid battery bank for household solar energy storage.
1. Understand Daily Energy Consumption
Start with a detailed load assessment:
- Lighting
- Appliances
- Refrigerators
- Internet equipment
- Emergency loads
Daily energy usage = Power (W) × Time (h)
2. Determine Required Backup Days
For residential solar systems:
- Grid-connected backup: 0.5–1 day
- Off-grid systems: 2–3 days
More backup days = larger battery bank.
3. Adjust for Depth of Discharge
Since lead-acid batteries should not exceed 50% DOD:
Required battery capacity = Daily consumption × Backup days ÷ 0.5
4. Series and Parallel Configuration
- Series connection increases voltage
- Parallel connection increases capacity
Ensure balanced wiring to avoid uneven charging.
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Conclusion
Accurate battery sizing ensures long service life, stable power output, and optimized solar system performance.
