Non-Bluetooth Lithium Battery Diagnostic SOP - Delayed charging

Purpose: Diagnose lithium battery failures (e.g., LiFePO₄) without Bluetooth or cell monitoring, to identify delayed charging or improper maintenance issues.

1. Measure Total Pack Voltage

Use a multimeter across terminals.
- 0–1V → BMS cutoff or fuse open.
- 5–10V → Deep discharge from long-term idle storage.
- 12.8–13.4V → Normal voltage, proceed to load test.
 → <10V is a typical sign of neglect (not charged for months).

2. Check Charger Reaction

Connect LiFePO₄ charger:
- No current flow → BMS undervoltage lock.
- Shuts off early → High internal resistance from deep discharge.
 - Slow voltage recovery → Damaged cells from sitting discharged.

3. Controlled Trickle Charge Test

Use bench supply (≤1A, 13.8V limit):
- Voltage jumps to ~13V, current <0.1A → Cells chemically inactive.
- Charging cuts repeatedly → BMS retrying due to imbalance.
 → Both patterns confirm prolonged undervoltage damage.

4. Open-Circuit Voltage Drop Test

After short charge, rest 1 hour and recheck voltage.
- Drop >0.5V → internal leakage from lithium plating.
 → Confirms storage neglect.

5. Load Test (if revived)

Apply ~0.2C discharge:
- Voltage collapses fast → high internal resistance (aging/neglect).
 - Stable voltage → likely short-term discharge only.

6. Physical and Contextual Evidence

- No swelling, burn marks, or corrosion → not shorted.
- Customer reports long storage or low cycle count → neglect.
 - Sale date >6 months ago, no recharge history → improper maintenance.

Summary Table:

Conclusion: If the pack shows low voltage, locked BMS, and no physical damage, the root cause is delayed charging or long-term idle storage, not a factory defect. Such cases fall under improper maintenance classification.