Electric Forklifts Operating in Low-temperature Environments: Battery Capacity Degradation Rate and Thermal Insulation Protection Measures

Low-temperature environments directly affect the chemical reaction rate of electric forklift batteries and the utilization rate of active materials, leading to battery capacity degradation and shortened endurance. Different types of batteries show significant differences in degradation rates, and corresponding thermal insulation protection measures need to be formulated in a targeted manner.

I. Low-temperature Capacity Degradation Rates of Different Battery Types

1. Lead-acid Batteries (Flooded/Maintenance-free Type)

Lead-acid batteries are highly sensitive to low temperatures, with capacity degradation increasing linearly as the temperature drops:

• When the temperature drops to 0℃, the battery capacity is about 70%–80% of the capacity at room temperature (25℃). The continuous operation time of a 2-ton electric forklift is reduced from 4–6 hours at room temperature to 3–4.5 hours.

• When the temperature drops to -10℃, the capacity decreases to 50%–60% of that at room temperature, and the operation time is further shortened to 2–3.5 hours.

• When the temperature is below -20℃, the capacity is only 30%–40% of the room temperature capacity. The internal resistance of the battery increases significantly, and the forklift may even fail to start. Forced discharge will cause irreversible damage to the electrode plates.

2. Lithium-ion Batteries (Lithium Iron Phosphate/Ternary Lithium)

Lithium-ion batteries have better low-temperature performance than lead-acid batteries, mainly due to the chemical stability of their electrode materials:

• For lithium iron phosphate batteries, at 0℃, the capacity retention rate is about 85%–90% of that at room temperature, with only a slight reduction in operation time.

• At -10℃, the capacity decreases to 70%–80% of the room temperature capacity, which can still meet most operational requirements.

• At -20℃, the capacity retention rate is about 60%–70%, much higher than that of lead-acid batteries at the same temperature.

Ternary lithium batteries have slightly better low-temperature performance than lithium iron phosphate batteries, with a further 5%–10% reduction in capacity degradation rate at the same temperature. However, due to safety limitations, they are rarely used in the industrial forklift field.

II. Thermal Insulation Protection Measures for Electric Forklift Batteries in Low Temperatures

The core principle of low-temperature protection is to increase the battery operating temperature, reduce battery internal resistance, and maintain chemical reaction activity. Measures can be implemented in three aspects: charging, operation, and storage.

1. Thermal Insulation During Charging: Ensure Charging Efficiency and Avoid Low-temperature Charging Damage

• Prioritize charging in room temperature environments: Set up charging areas in indoor warehouses or build insulated charging sheds, with the ambient temperature controlled between 10℃ and 25℃. Avoid direct charging in open low-temperature environments. Low-temperature charging is prone to cause plate sulfation in lead-acid batteries and lithium plating in lithium batteries, resulting in permanent capacity loss.

• Adopt intelligent temperature-controlled chargers: Equip with special chargers with heating functions. The chargers automatically preheat the battery pack before charging, and start the charging process only when the battery temperature rises above 5℃. Real-time monitor the battery temperature during charging and dynamically adjust the charging current to prevent battery damage caused by high-current charging at low temperatures.

• Extend the charging standing time: The battery’s charge acceptance ability decreases in low temperatures. Do not disconnect the power immediately after charging is completed; maintain a floating charge state for 1–2 hours. Use the heat generated by the floating charge current to further increase the battery temperature and enhance the endurance at the initial stage of operation.

2. Thermal Insulation During Operation: Reduce Battery Heat Loss and Maintain Working Temperature

• Install battery insulation covers/boxes: Customize sealed insulation covers for battery packs using flame-retardant insulation cotton or polyurethane foam materials to isolate external cold air. For medium and heavy-duty electric forklifts, install battery insulation boxes with heating functions, equipped with low-power heating sheets powered by the forklift’s power supply, to maintain the battery operating temperature above 10℃.

• Optimize operation rhythm and avoid frequent high-current discharge: High-current discharge of batteries at low temperatures will intensify capacity degradation and heat consumption. During operation, maintain a uniform speed as much as possible, reduce sudden acceleration, sudden braking, and frequent lifting actions. During long-term heavy-load operations, stop the forklift for 10–15 minutes every 1–2 hours to allow the battery to naturally recover its temperature and avoid over-discharge.

• Equip with spare batteries for rotation operation: For multi-shift continuous operation scenarios, prepare 2–3 sets of spare batteries, store and preheat them in room temperature environments. Replace the used battery immediately after it runs out of power. This not only ensures operation efficiency but also prevents over-discharge of the battery in low temperatures.

3. Thermal Insulation During Storage: Prevent Long-term Low-temperature Battery Depletion

• Store idle batteries in warehouses: When an electric forklift is out of service for a long time (more than 2 days), remove the battery and store it indoors, with the storage ambient temperature controlled above 0℃. Avoid storing the battery in an outdoor low-temperature environment with insufficient power.

• Regularly recharge to maintain a full-charge state: The self-discharge rate of batteries accelerates during low-temperature storage. Recharge lead-acid batteries every 15 days and lithium batteries every 30 days to ensure the battery power remains above 80%, preventing plate sulfation or triggering of the protection mechanism due to excessively low voltage in lithium batteries.

• Avoid direct contact between batteries and the ground: Place wooden boards or insulation pads under the batteries during storage to isolate cold conduction from the ground and reduce temperature loss at the bottom of the batteries.

III. Supplementary Notes

• The shortened battery endurance in low-temperature environments is a normal phenomenon. Plan the operation route and workload in advance before operation to avoid power outages midway.

• It is strictly prohibited to charge or heat frozen batteries. Transfer the batteries to a room temperature environment to thaw before operation; otherwise, it may cause battery bulging, leakage, or even explosion.

• Regularly inspect the battery thermal insulation protection devices, replace damaged insulation covers in a timely manner, and ensure that components such as heating sheets and temperature control sensors work normally.