Capacity & Discharge Testing

Overview

Capacity and discharge testing verifies that every battery delivers its rated energy output under real-world conditions. We conduct comprehensive discharge curve analysis, rate capability testing, and self-discharge measurement to ensure our solar lighting systems perform as specified.

Test Methodology

1. Full Capacity Verification

• Charge to 3.65V/cell at 0.5C, hold until current <0.05C
• Rest period: 1 hour
• Discharge to 2.5V/cell at 0.2C (5-hour rate)
• Record actual capacity (Ah) and energy (Wh)
• Acceptance: ≥98% of rated capacity for new cells

2. Rate Capability Testing

Discharge at various rates to evaluate performance under different load conditions:

3. Self-Discharge Measurement

• Fully charge battery, then store at 25°C
• Measure capacity at 7, 14, 30, 60, and 90 days
• Acceptance: <3% per month for LiFePO4
• This ensures batteries maintain charge during extended cloudy periods

4. Discharge Curve Analysis

We analyze the complete voltage-vs-capacity discharge curve to verify:

• Flat voltage plateau (>90% of capacity delivered within 0.2V range)
• Knee point location (sharp voltage drop indicates end of useful capacity)
• Consistency across cells in a pack (ΔV < 50mV)
• Temperature rise during discharge (ΔT < 15°C at 1C rate)

Battery Pack Quality Checks

• Cell matching: capacity difference <2% within a pack
• Internal resistance matching: ΔR < 2mΩ
• Voltage matching: ΔV < 20mV at 50% SOC
• BMS calibration: voltage measurement accuracy ±10mV