Judgment Criteria for Undervoltage Protection Status of Electric Forklift Batteries

To determine whether a battery is in the undervoltage protection state, it is necessary to combine three core indicators: dashboard signals, equipment operating status, and measured voltage data, while distinguishing the different protection characteristics of lead-acid batteries and lithium batteries. The specific judgment methods are as follows:

1. Intuitive Judgment: Dashboard and Audio-Visual Alarm Signals

This is the most direct basis for judgment, requiring no professional tools and enabling quick identification by operators.

2. Operating Status Judgment: Equipment Action Characteristics

This method assists in determining the protection state by observing the response of the forklift's power and hydraulic systems, and is applicable for emergency judgment when the dashboard malfunctions.

Action Characteristics of Early-Warning Protection

• Power is significantly reduced during driving, with no response to sudden acceleration; the maximum speed drops to 50%-70% of the rated value.
• The lifting speed of the forks slows down, with jamming during heavy-load lifting; no-load lifting can barely operate.
• The forklift can travel a short distance to the charging area, and continuous operation is prohibited.

Action Characteristics of Power-Limitation Protection

• The drive system is completely locked, with no power output when the accelerator pedal is pressed.
• The hydraulic system only retains the no-load lowering function; it cannot lift goods, and auxiliary functions such as side shifting/ clamping become ineffective.
• The steering assist is weakened (for electric power-assisted models), resulting in increased steering resistance.

Action Characteristics of Shutdown/Lockout Protection

• The entire vehicle has no power, and the key switch cannot start the drive system.
• The hydraulic system completely fails, and the forks cannot be lifted or lowered (for lead-acid batteries in shutdown protection, the forks can be lowered by manual pressure relief).
• When a lithium battery in lockout protection is connected to a charger, there is no charging current, and it needs to be unlocked with special equipment.

3. Precise Judgment: Measured Voltage Data (Responsible Entity: Maintenance Technician)

Use a multimeter or battery internal resistance tester to measure the battery voltage, and determine the protection state in combination with threshold standards. This method is applicable for fault troubleshooting and precise positioning.

3.1 Measured Judgment Standards for Lead-Acid Batteries

Measurement Method: Disconnect the battery load, set the multimeter to DC voltage mode, connect the positive and negative terminals to the battery's total positive and total negative terminals respectively, and measure the voltage value after 5 minutes of standing. Randomly measure the voltage of 3-5 single cells and use the minimum value for judgment.

3.2 Measured Judgment Standards for Lithium Batteries

Measurement Method: Read the voltage of all cells through the BMS diagnostic interface (recommended method). If there is no diagnostic interface, disassemble the battery pack, measure the voltage of each cell string one by one, and record the minimum value.

4. Judgment Correction for Low-Temperature Environment in Winter

Battery capacity decreases at low temperatures, and the protection threshold will be dynamically adjusted upward. The standards need to be corrected during judgment:

• When the ambient temperature is < 5℃, the early-warning judgment threshold for lead-acid batteries is adjusted upward to 92% of the rated voltage, and the early-warning threshold for lithium battery cells is adjusted upward to 3.1V.
• When the temperature is < -10℃, if the forklift experiences power limitation but the voltage value is close to the normal threshold, it should be preferentially judged as low-temperature protection rather than undervoltage protection, and the voltage should be remeasured after moving the forklift to a normal-temperature environment.

5. Judgment Misunderstandings and Precautions

• Mistaking charging protection for undervoltage protection: The protection triggered by excessively high battery voltage during charging will display an "Overvoltage Alarm", which is distinguishable from the undervoltage alarm signal.
• When signal distortion occurs due to dashboard failure, the measured voltage must be taken as the final judgment basis.
• The lockout protection of lithium batteries requires unlocking by professional personnel; it is prohibited to forcibly start the battery by short-circuiting it.