As the core transportation equipment for urban and rural freight, field operations and short-distance travel, electric tricycles have long been operating under complex working conditions such as heavy-load start-up, slope climbing operation, frequent start-stop and all-weather outdoor use, which put forward higher requirements for the stability and durability of energy storage systems. Lithium batteries have become the mainstream energy storage configuration for tricycles due to their advantages of high energy density, strong power output and long cycle life. The working state of battery cells is the core basis that directly determines the vehicle’s dynamic performance, cruising capability, operation safety and battery service life. The cell working state covers the ion activity, voltage stability, internal resistance change and overall balance of the battery during charging, discharging, standing and working in high and low temperature environments. Most common problems encountered by users, such as weak load-bearing power, sudden cruising range drop, abnormal charging, random power failure and power attenuation in winter, are essentially performance failures caused by unbalanced cell working state. In-depth mastery of cell working rules in different scenarios, accurate identification of abnormal states, and maintenance of stable cell operation through scientific maintenance are the keys to extending battery service life, reducing operation and maintenance costs and ensuring stable vehicle operation.

　　The steady working state under standard normal working conditions is the optimal operation mode of lithium batteries and the foundation for long-term equipment use. Under normal temperature, light load and standardized charge and discharge conditions, the lithium iron phosphate cells equipped in electric tricycles can complete stable and reversible deintercalation and migration of lithium ions between positive and negative electrodes. During charging, lithium ions are evenly precipitated from the positive electrode, smoothly migrate through electrolyte and diaphragm channels and embed into the negative electrode graphite layer structure. The internal internal resistance remains stable at a low level, the voltage rises uniformly without sudden fluctuations. During discharging, lithium ions move in reverse to release electric energy with stable current output and voltage platform, which can continuously match the power demand of vehicle uniform driving and light-load commuting. In the steady working state, the voltage difference between single cells of the entire battery pack is extremely small, and the capacity, internal resistance and temperature parameters of each cell are highly unified. The battery management system does not need frequent current limiting protection, the power statistics are accurate, the cruising range is consistent with the actual situation, and there is no virtual power or power jump problem, which is the working mode with the longest battery cycle life and the lowest loss.

　　The heavy-load dynamic imbalance state is the most common non-standard working state of electric tricycles and the main inducement of premature cell aging. As the core function of tricycles is cargo transportation, frequent full-load start-up, steep slope climbing and continuous heavy-load driving will make the instantaneous discharge current far exceed the standard value, completely breaking the steady operation balance of cells. During high-intensity discharge, the migration rate of internal lithium ions increases sharply, the electrolyte flow is disordered, the local temperature rises rapidly, and the load of single cells is uneven. Some weak cells enter the voltage drop state in advance, leading to the collapse of the overall voltage platform of the battery pack. Long-term repeated heavy-load imbalance will cause continuous increase of cell internal resistance, continuous thickening of the negative electrode passivation layer, reduction of effective active ions, and gradual expansion of voltage difference between cells. The intuitive manifestations include weak vehicle start-up power, insufficient climbing power, greatly reduced cruising range under the same power and falsely high full power state. Without timely intervention and correction, it will cause irreversible capacity attenuation, completely damage the normal working state of cells.

　　The temperature-induced abnormal state is an invisible and easily overlooked failure inducement. Ambient temperature directly reshapes the working state of cells. Lithium battery cells are highly sensitive to temperature changes, and extreme temperatures will completely change the internal chemical reaction rate and ion migration efficiency, leading to distorted working state. Working or charging immediately after outdoor exposure and high temperature in summer will cause continuous rise of internal cell temperature, accelerated electrolyte decomposition and aging, intensified internal side reactions. The cells work in a high-temperature overload state, which not only accelerates capacity loss, but also greatly increases the risk of battery bulging and thermal runaway. In low-temperature winter environments, the electrolyte viscosity increases, the resistance of lithium ion migration rises sharply, and cell activity is greatly reduced, entering a low-temperature and low-energy working state, manifested as reduced vehicle cruising range and weak power. Forcing heavy-load discharge or low-temperature fast charging at this time will cause lithium precipitation and lattice damage on the negative electrode, resulting in permanent cell damage. Even if the temperature returns to normal later, the working state cannot be fully recovered, forming permanent performance defects.

　　The static dormancy and power deficit failure state are common abnormal cell working conditions during vehicle idling. Electric tricycles have obvious seasonal idle characteristics. When left idle for a long time in off-seasons such as autumn and winter, the cell state will gradually decay with the standing time. Batteries have a slight self-discharge characteristic. Long-term static storage with full power keeps cells in a long-term high-pressure saturated working state, and internal side reactions slowly consume active substances, leading to gradual decline of cell activity. Long-term storage with insufficient power will make the cells enter a deep dormant state after the residual power is exhausted, with nearly stagnant ion movement and passivated negative electrode materials, resulting in sharp increase of internal resistance. Mild dormancy can be recovered through standard charge and discharge cycle activation, while long-term deep power deficit dormancy will lead to permanent deactivation of some cells and scrap of single cells, destroying the working balance of the entire battery pack, causing faults such as incomplete charging, rapid power discharge and frequent protective power failure of equipment, and directly leading to premature battery scrapping.

　　The disordered working state caused by improper charge and discharge operation is the most common loss source in daily use. Irregular charging will completely disrupt the cell working rhythm. Using non-original fast chargers and high-current charging will cause sudden rise of cell voltage and local overheating, unbalanced charging of single cells, overcharging of some cells and undercharging of others, resulting in disordered working state of the entire battery pack. Overnight floating charging and long-term overcharging keep cells in a long-term high-pressure overload state, continuously consuming active substances and accelerating aging and attenuation. The daily habit of deep discharge and charging after power exhaustion will make cells work in a long-term power deficit stress state, repeatedly damaging the electrode structure and aggravating internal resistance deterioration. Batteries that work in a disordered state for a long time will have continuously expanding cell voltage difference, declining capacity and lost working stability, resulting in various faults such as abnormal heating during charging, power jump and intermittent power, seriously shortening the battery service life.

　　Accurate judgment of cell working state can be quickly completed through vehicle performance and basic operation and maintenance observation. In the normal steady state, the battery charges uniformly with slight temperature rise, stable cruising range and linear power output; the heavy-load imbalance state is manifested as obvious voltage drop under heavy load, weak climbing power and fluctuating cruising range; the temperature abnormal state is manifested as fast heating during high-temperature charging and sharp power drop at low temperature; the dormant failure state is manifested as slow charging, serious virtual power and fast power loss after long-term idling. The core of daily maintenance is to maintain a stable cell working environment and avoid various abnormal working conditions. Try to start smoothly and drive uniformly in daily operation to reduce instantaneous heavy-load impact; avoid deep power deficit and long-term full power storage, and maintain the optimal power range of 20% to 80%; avoid high-intensity operation and immediate charge and discharge in extreme temperature environments; keep medium power of about 50% for idle vehicles, and complete a standard charge and discharge cycle every two to three months to activate cell activity and balance cell voltage difference.

　　Relying on the intelligent protection function of the battery management system can timely correct abnormal cell working states and ensure synchronous steady operation of the entire cell pack. The system can collect the real-time voltage, current and temperature data of each cell. Once abnormal working conditions such as excessive single-cell voltage difference, over-temperature, over-current and over-voltage are detected, it will automatically limit current and cut off power for protection to avoid continuous cell damage. Regular cell balance maintenance should be carried out to correct single-cell parameter deviations, narrow the voltage difference gap, and keep the entire cell pack in a synchronous working state. Standardizing working conditions, avoiding abnormal losses and adhering to regular calibration maintenance can maintain the optimal working state of cells for a long time, maximize the rated performance and cycle life of batteries, ensure stable power output of electric tricycles in various heavy-load and high-frequency operation scenarios, and greatly reduce equipment operation and maintenance and replacement costs.