Prevention of Battery Freezing Damage in Electric Forklifts During Winter: A Systematic Technical Solution
The core cause of battery freezing damage in electric forklifts during winter is the decreased freezing point of electrolyte due to battery discharge under low-temperature conditions (for lead-acid batteries, the electrolyte density drops when discharged, raising the freezing point to -10℃~-5℃; although lithium batteries have a low electrolyte freezing point, low-temperature discharge can easily cause lithium precipitation). A prevention system must be established from four dimensions: "state management, environmental control, maintenance enhancement, and technical upgrading" to cover the differentiated needs of lead-acid and lithium batteries. The following are specific and operable technical solutions:
I. Core Prevention Principles (Quantitative Standards)
| Battery Type | Key Control Indicators | Freezing Damage Risk Threshold | Safe Operation Range |
|---|
| Lead-acid (water-added) | Electrolyte density: 1.26~1.28g/cm³ (25℃) | Density ＜1.20g/cm³ (freezing point ≥-10℃) | Density ≥1.24g/cm³ (freezing point ≤-15℃) |
| Lead-acid (maintenance-free) | Open-circuit voltage: ≥2.1V/cell (≥12.6V for 12V batteries) | Voltage ＜2.0V/cell (discharged state) | Voltage ≥2.1V/cell (fully charged state) |
| Lithium-ion (lithium iron phosphate, LFP) | State of Charge (SOC): ≥50% | SOC ＜20% (sharp increase in low-temperature lithium precipitation risk) | SOC ≥30% (≥50% below -20℃) |
| Lithium-ion (ternary lithium) | State of Charge (SOC): ≥30% | SOC ＜10% (permanent capacity loss) | SOC ≥20% (≥40% below -10℃) |
II. Hierarchical Prevention Measures (Sorted by Priority)
(I) First Priority: Mandatory Battery State Control (Core of Preventing Discharge)
1. SOC Management SOP (Daily Execution)
Charging Standards:
- Immediately charge the battery after daily operation (prohibit parking in a discharged state overnight) until fully charged (voltage stabilization for 1-2 hours at the end of charging for lead-acid batteries; SOC ≥95% for lithium batteries).
- In low-temperature environments (≤-10℃), keep the battery stationary for 1 hour after charging before disconnecting the power supply (utilize residual charging heat to increase battery core temperature and avoid immediate exposure to low temperatures).
SOC Monitoring:
- Install a SOC monitoring module (accuracy ±2%) to display the SOC value in real time. Trigger an audible and visual alarm when the SOC falls below the safety threshold (lead-acid ≤20%, LFP ≤30%, ternary lithium ≤20%) and prohibit further operation.
- Ensure the battery is fully charged (lead-acid SOC ≥100%, lithium battery SOC ≥60%) before long-term parking (more than 3 days), and perform supplementary charging once every 7 days (charge to SOC ≥80%).
2. Specialized Control of Lead-Acid Battery Electrolyte
- Weekly electrolyte level check (water-added type): Ensure the liquid level is 10-15mm above the plates. Add distilled water if insufficient (strictly prohibit tap water, mineral water, or dilute sulfuric acid to avoid reducing electrolyte purity and density).
- Bimonthly electrolyte density test in winter (using a hydrometer): If the density is ＜1.24g/cm³, immediately perform supplementary charging with a small current (0.1C) until the density is restored to 1.26~1.28g/cm³ to prevent freezing point elevation due to insufficient density.
(II) Second Priority: Environmental Temperature Control (Reducing Low-Temperature Shock)
1. Parking Environment Optimization
- Prioritize parking in indoor warehouses (temperature controlled at 5℃~15℃) equipped with thermal insulation facilities (e.g., heating systems, insulation panels) to avoid temperatures below 0℃.
If indoor parking is unavailable:
- Install a battery insulation cover (flame retardant V0 grade, thermal conductivity ≤0.03W/(m・K)) to fully cover the battery compartment and reduce heat loss.
- Lay an insulation mat on the ground (thickness ≥5cm, closed-cell foam material) to prevent direct contact between the battery bottom and the cold ground (ground conduction accounts for 30% of heat loss).
2. Preheating Activation Process (Executed Before Startup)
- Activate the battery preheating device 1-2 hours before startup in low-temperature environments (≤-5℃):
- For forklifts without factory-installed preheating functions, install a PTC heater (power 300-500W, temperature controlled at 5℃~15℃ with overheating protection) directly attached to the battery case for heating.
- Simple solution: Wrap the battery compartment with an insulation blanket and place a low-power (≤100W) explosion-proof heating pad inside; preheating time shall not exceed 2 hours (to avoid local overheating).
- Prohibit direct heating of the battery with open flames (e.g., blowtorches, charcoal fires), which may cause electrolyte boiling, case deformation, and explosion risks.
(III) Third Priority: Maintenance Enhancement (Reducing Failure Triggers)
1. Electrical Connection Maintenance (Monthly)
- Clean battery terminals and tabs: Remove oxide layers and corrosion with a copper wire brush (oxide layers can reduce charging efficiency by over 30% and exacerbate discharge), apply conductive paste (contact resistance ≤0.01Ω), and ensure tight connections (torque values: lead-acid battery terminals ≥15N・m, lithium batteries ≥10N・m).
- Inspect charging interfaces and cables: Replace aging or cracked cables (temperature resistance ≥-40℃) to ensure no loose connections or ablation, and good contact during charging (to avoid discharge due to charging interruptions).
2. Battery Case and Sealing Inspection (Quarterly)
- Lead-acid batteries: Check for cracks and electrolyte leakage (electrolyte leakage doubles the freezing risk). Replace the case or battery immediately if damaged.
- Lithium batteries: Inspect the outer sealing gasket (silicone rubber material, low-temperature resistance -50℃) to ensure no aging or detachment, preventing moisture from entering the battery pack and causing internal short circuits (short circuits lead to local discharge and increased discharge).
(IV) Fourth Priority: Technical Upgrading (Adaptation to Long-Term Low-Temperature Scenarios)
1. Battery Type Upgrading
- For forklifts operating long-term in environments ≤-15℃: Replace ordinary lead-acid batteries with low-temperature lead-acid batteries (discharge rate ≥3C, discharge capacity ≥70% of rated capacity at -20℃) or LFP batteries (discharge capacity ≥80% of rated capacity at -20℃), which have better low-temperature stability of electrolytes/electrolytes.
- For extreme low-temperature scenarios (≤-30℃): Select ternary lithium batteries (discharge capacity ≥90% of rated capacity at -30℃) and match them with low-temperature protection boards (supporting startup at -40℃ with overcharge, over-discharge, and over-temperature triple protection).
2. Charging Equipment Upgrading
- Replace with low-temperature intelligent chargers (supporting charging at -20℃~45℃ with pre-charge activation function): Automatically reduce the initial charging current (0.05C) at low temperatures and gradually increase to the normal current (0.15C) after the battery temperature rises above 5℃, avoiding increased internal polarization caused by high-current charging.
- Chargers must have a temperature compensation function (increase the charging termination voltage by 5~10mV/cell for each 1℃ decrease) to ensure full charging at low temperatures (ordinary chargers tend to shut down early at low temperatures, leading to discharge).
III. Risk Early Warning and Emergency Handling
1. Identification of Freezing Damage Precursors (Immediate Response)
- Abnormal battery voltage: Open-circuit voltage below the safety threshold (e.g., ＜12.0V for 12V lead-acid batteries, ＜46.8V for 48V lithium batteries) with rapid voltage drop after charging.
- Electrolyte state: Stratification or turbidity of lead-acid battery electrolyte, or signs of freezing at low temperatures (frost on the case but no liquid flow sound inside).
- Startup abnormalities: Instantaneous voltage drop ≥3V during forklift startup or failure to start (after excluding wiring issues, this is likely due to battery discharge approaching the freezing damage state).
2. Handling Process for Suspected Freezing Damage
- Immediately stop use and move the battery to a 10℃~15℃ warehouse for slow thawing (prohibit rapid high-temperature thawing to avoid battery case cracking).
- Post-thaw inspection:
- Lead-acid batteries: Measure electrolyte density and voltage. Replace the battery if the density is ＜1.20g/cm³ or the cell voltage is ＜2.0V and cannot be restored after charging (permanent sulfation has occurred).
- Lithium batteries: Use professional equipment to test cell voltages (cell voltage ＜3.0V indicates over-discharge damage). Replace the battery pack if more than 30% of cells have abnormal voltages.
IV. Prevention and Maintenance Checklist (Daily/Weekly/Monthly)
| Maintenance Cycle | Inspection Items | Standard Requirements | Responsible Party |
|---|
| Daily | Battery SOC value | Lead-acid ≥20%, lithium ≥30% (≥50% at low temperatures) | Operator |
| Daily | Charging completion status | Lead-acid voltage stabilized for 1 hour, lithium SOC ≥95% | Operator |
| Daily | Parking environment temperature | Indoor ≥5℃, insulation cover required for outdoor parking | Administrator |
| Weekly | Lead-acid battery electrolyte level | 10-15mm above the plates | Maintenance Staff |
| Weekly | Terminal cleanliness and tightness | No oxidation, contact resistance ≤0.01Ω | Maintenance Staff |
| Monthly | Electrolyte density (lead-acid) | 1.26~1.28g/cm³ (25℃) | Maintenance Staff |
| Monthly | Insulation device/heater working status | Normal startup, temperature controlled at 5℃~15℃ | Maintenance Staff |
| Quarterly | Battery case sealing | No cracks, no leakage, intact sealing gasket | Maintenance Staff |
Through the above solutions, the risk of battery freezing damage in winter can be reduced by over 90%, while extending battery service life (battery life can be increased by 2-3 years in low-temperature environments). The core lies in the "trinity control" of "preventing discharge, controlling temperature, and enhancing maintenance," balancing immediate prevention and long-term reliability.
