Winter Electric Forklift Battery Freeze Damage Symptoms

The symptoms of freeze damage in winter electric forklift batteries (lead-acid/lithium-ion) can be categorized into three types: intuitive external characteristics, electrical performance abnormalities, and starting/operation failures. Based on structural differences between the two battery types, the following are specific identifiable symptoms (including quantitative judgment criteria) to facilitate rapid troubleshooting:

I. Intuitive External Characteristics (Tool-Free, Visible/Tactile Judgment)

(I) Lead-Acid Batteries (Flooded/Maintenance-Free)

1. Case Deformation or Bulging

• Symptoms: ABS battery case exhibits protrusions or bulges, with potential cracks at corners; severe cases involve electrolyte leakage (pale yellow liquid with an irritating odor).
• Cause: Electrolyte expands by ~9% when frozen at low temperatures, rupturing the case; or internal short circuits after freezing cause gas generation, leading to case bulging.

2. Signs of Electrolyte Freezing

• Symptoms:
  • Flooded lead-acid: Open the filling cap to observe solidified electrolyte or ice crystals; no liquid flow sound when shaking the battery.
  • Maintenance-free lead-acid: Check the indicator window—black color without liquid reflection indicates potential freezing.
• Environmental Correlation: High probability when ambient temperature ≤ -10℃ (in a discharged state).

3. Abnormal Terminal Corrosion

• Symptoms: Thick white/green corrosion on terminals and lugs, spreading to cable connectors with a corrosion rate significantly higher than normal.
• Cause: Reduced battery sealing after freezing allows electrolyte leakage or moisture ingress, accelerating metal corrosion.

(II) Lithium-Ion Batteries (LFP/NCM)

1. Housing Seal Failure

• Symptoms: Frost, water droplets, or electrolyte leakage (colorless, transparent liquid with a slight sweet odor) at housing gaps; protrusion or rupture of explosion-proof valves on some battery packs.
• Cause: Low-temperature freezing deforms internal structures, damaging sealing gaskets or housing welds.

2. Abnormal Temperature

• Symptoms: Battery pack remains persistently cold (no normal heat dissipation) when ambient temperature ≥ 0℃, or local overheating spots occur (caused by internal short circuits after freezing).
• Comparison: Normal lithium-ion batteries gradually warm to above 5℃ after startup/charging even when parked in low temperatures.

II. Electrical Performance Abnormalities (Simple Tools Required, Core Judgment Basis)

(I) Voltage Abnormalities (Measured with Multimeter, Key Quantitative Indicators)

1. Low Static Voltage

• Lead-Acid Batteries:
  • 12V cell static voltage < 12.0V (normal ≥ 12.6V); 48V total voltage < 48.0V (normal ≥ 50.4V).
  • Cell voltage deviation > 0.3V (e.g., 1 cell < 2.0V among 6 cells, others ≥ 2.1V).
• Lithium-Ion Batteries:
  • Cell voltage < 3.0V (normal ≥ 3.2V); total voltage > 10% lower than rated voltage (e.g., 48V battery < 43.2V).
  • Voltage drops rapidly after charging (≥ 2V ｄｒｏｐ within 1 hour).

2. Abnormal Charging

• Symptoms:
  • Charger shows "fault" or "disconnected" with no charging current.
  • Charger indicates "full" immediately after 1-2 hours, but voltage drops sharply when disconnected.
• Cause: Severe internal polarization or cell damage after freezing prevents current acceptance; some chargers trigger protection due to extremely low battery voltage.

(II) Significant Internal Resistance Increase

• Symptoms: Measured with a resistance meter:
  • Lead-acid: Cell internal resistance > 30mΩ (normal ≤ 15mΩ).
  • Lithium-ion: Cell internal resistance > 100mΩ (normal ≤ 50mΩ).
  • Resistance deviation > 50mΩ between cells in the same pack.
• Impact: Near-zero charging efficiency, inability to store power, and instant voltage ｄｒｏｐ during startup.

III. Starting & Operation Failures (Directly Observed During Forklift Use)

1. Failure to Start or Instant Power Cut After Startup

• Symptoms:
  • No instrument display or "battery undervoltage" alarm when power is turned on.
  • No response when accelerating, or power cuts off within 1-2 seconds (controller protection triggered by low voltage).
• Comparison: Normal low-temperature startup shows temporary low-voltage display but stabilizes after preheating.

2. Severe Power Loss (Early Freeze Damage Symptom)

• Symptoms:
  • Forklift moves slowly but cannot lift loads or climb slopes.
  • Instrument voltage drops rapidly during operation (e.g., 48V battery < 45V after 5 minutes), leading to power cut.
• Cause: Permanent capacity loss (≥ 50% typically) after freezing, preventing normal current supply.

3. Charging Protection Faults

• Symptoms:
  • Charger frequently shuts down with "overtemperature protection", "overcurrent protection", or "battery abnormal" alerts.
  • Some smart chargers lock permanently and cannot restart charging.
• Difference: Normal low-temperature charging involves gradual current increase without frequent shutdowns.

IV. Key Criteria for Irreversible Damage (Avoid Misjudgment: Freeze Damage vs. Normal Low-Temperature Effects)

Summary: Rapid Judgment Process

1. External Observation: Check for case deformation, leakage, or freezing → Initial judgment.
2. Voltage Measurement: Verify if static voltage is below the thresholds above → Core confirmation.
3. Charging Test: Check for abnormal charging or irreversible voltage ｄｒｏｐ → Final determination.

Conclusion: If any 1 external characteristic + 1 electrical performance abnormality occur, the battery is almost certainly freeze-damaged. Immediately stop use to avoid short circuits or fire risks from continued charging/starting. ｒｅｐｌａｃｅ the battery directly (freeze damage is irreversible and uneconomical to repair).