Hazards of Undercharged Operation of Electric Forklift Batteries in Winter and Standard Operating Procedures for Consequence Disposal
1. Core Definition
Undercharged operation of batteries in winter refers to a state where the depth of discharge exceeds 70% (i.e., the remaining power is less than 30%) or the battery is in a long-term low-power cycle of "usage before full charge". Low-temperature environments will amplify the hazards of undercharging, causing more severe irreversible damage than under normal temperatures.
2. Specific Hazards by Battery Type
(1) Lead-Acid Batteries (Mainstream Configuration for Electric Forklifts)
Irreversible Damage Caused by Plate Sulfation
In low temperatures, the electrolyte has high viscosity and slow ion migration speed. When the battery is undercharged, hard lead sulfate crystals will form on the surface of the plates, clogging the plate pores.
- Short-term impacts: Sudden drop in battery capacity by 20%–40%, reduced charge acceptance, prolonged charging time and failure to reach full charge.
- Long-term hazards: The crystals cannot be removed by regular charging, and will gradually cover the active materials of the plates, leading to plate softening and shedding. The cycle life of the battery is directly shortened by 30%–50%. A battery that could originally last 2–3 years may be scrapped within 1 year if frequently undercharged in winter.
Exacerbated Plate Polarization and Corrosion
In an undercharged state, the internal voltage of the battery is unstable, resulting in a "polarization phenomenon". The positive plates are prone to oxidative corrosion, and the negative plates suffer from hydrogen embrittlement, which increases the risk of internal short circuits of the battery. In severe cases, liquid leakage, bulging or even fire may occur.
Complete Loss of Low-Temperature Starting Performance
The internal resistance of an undercharged battery increases sharply in environments below -10℃, failing to provide the instantaneous large current required for forklift startup, leading to startup failure and directly affecting operational continuity.
(2) Lithium Batteries (High-End Forklift Configuration)
Safety Risks Caused by Lithium Metal Deposition
In low temperatures and undercharged conditions, lithium ion intercalation and deintercalation are insufficient. Forcing charging or continuing discharge at this time will cause metallic lithium dendrites to deposit inside the battery cells.
- Short-term impacts: Sudden drop in battery voltage, premature termination of discharge, insufficient forklift power and frequent shutdowns.
- Long-term hazards: Lithium dendrites will pierce the battery cell separators, causing internal short circuits, which trigger battery bulging, spontaneous combustion or even explosion, and this damage is completely irreversible.
Risk of BMS System Failure
When the battery voltage is below the protection threshold in an undercharged state, the Battery Management System (BMS) may misjudge or malfunction, failing to monitor temperature and current parameters normally, which further amplifies safety hazards.
Cliff-Like Drop in Cycle Life
The normal cycle life of lithium batteries is about 1,500–2,000 cycles. Frequent undercharging in winter will shorten the cycle life to 500–800 cycles, resulting in premature battery scrapping.
3. Indirect Hazards (Impacts on Equipment and Operations)
Damage to Forklift Power Systems
Unstable output voltage of undercharged batteries will impact core components such as forklift motors and controllers, leading to excessive motor starting current, frequent controller errors and shortened service life of the electronic control system.
Reduced Operational Safety and Efficiency
Undercharged forklifts have insufficient power, with drastically reduced climbing and load-bearing capacity, which are prone to safety accidents such as "sliding downhill and cargo falling".Frequent shutdowns for charging will cause operational interruptions. The single charging time in winter is 1–2 hours longer than that in summer, directly reducing operational efficiency by 20%–30%.
Sharp Increase in Maintenance Costs
Premature battery scrapping and electronic control system maintenance caused by undercharging will increase the winter maintenance cost of a single forklift by 50%–80%.
4. Abnormal Disposal Procedures (Response Measures After Detecting Undercharging)
| Abnormal Condition | Operation Steps | Responsible Party | Execution Time Limit |
|---|
| Power below 30% during operation | Stop operation immediately and turn off the forklift power supply; Drive slowly to the charging area (no sudden acceleration); Record the undercharging time and operating conditions
| Forklift Operator | Within 5 minutes |
| Signs of battery sulfation/lithium deposition | Lead-acid batteries: Perform equalizing charging (increase charging voltage by 0.1–0.2V and extend charging time by 2–3 hours); Lithium batteries: Stop using immediately and contact the manufacturer for testing; Prohibit further use
| Equipment Maintenance Technician | Implement immediately upon detection |
| Battery bulging/liquid leakage | Isolate the faulty battery and set up warning signs; Cover leaked liquid of lead-acid batteries with sand; protect lithium batteries with dry powder fire extinguishers; Contact professional institutions for recycling and disposal
| Safety Administrator | Implement immediately upon detection |
