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Buying LiFePO4 cells or packs? Don’t trust the label — verify. This guide shows you how to test actual capacity and internal resistance with methods ranging from a basic multimeter to professional grading equipment.
Why Test? The Label Isn’t Enough
Capacity fraud is common: rewrapped B-grade cells sold as A-grade, inflated Ah ratings, missing test data. Testing protects your purchase. See our Grade A/B verification guide and fake capacity guide.
Capacity Testing: The Gold Standard
What You Need
- LiFePO4-compatible charger
- Electronic load or capacity tester
- Multimeter
- Temperature-stable environment (15–30°C)
Test Protocol
- Charge to 3.65V per cell (current tapering to 0.05C)
- Rest 30+ minutes
- Discharge at 0.2C (or datasheet rate) to 2.5V
- Record delivered amp-hours
Compare against rated capacity. Grade A should deliver ≥95% of rated Ah.
Internal Resistance Testing
AC 1kHz Method (Preferred)
Use a dedicated IR tester. Measure all cells at the same SoC and temperature. Typical values: 280Ah-class ~0.15–0.3mΩ; 100Ah-class ~0.3–0.5mΩ.
Critical Rules
- Same SoC for every cell
- Same temperature
- Never mix AC and DC readings
Three Tiers of Testing
| Tier | Equipment | Best For |
|---|---|---|
| Basic | Multimeter + charger | Spot checks |
| Intermediate | + IR tester | Small batches |
| Professional | + grading cabinet | Volume purchasing |
Self-Discharge Test
Fully charge, record voltage, store 15–30 days at stable temperature. Fast-decay outliers indicate high self-discharge — reject them. See our cell selection guide for matching criteria.
Frequently Asked Questions
Can I test with just a multimeter?
For voltage and basic screening, yes. For real capacity verification, you need a controlled discharge.
What’s an acceptable capacity variance?
±2–5% within a pack, depending on application criticality.
How do I know if my tester is accurate?
Calibrate against a known-good cell; verify at stable temperature.
Contact LJY Energy for cells with documented test reports.
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