How does the lithium battery protection board prevent battery voltage from overcharging through overcharge protection?
Publish Time: 2025-09-25
Lithium batteries, as the most common energy carrier in modern electronic devices, are highly sought after for their high energy density and long cycle life. However, they also place extremely high demands on safety during the charging and discharging process. Overcharging is one of the most dangerous conditions in lithium battery use, potentially leading to bulging, leakage, and even fire and explosion. The lithium battery protection board plays a crucial role in effectively addressing this risk.Overcharge protection is a core function of the lithium battery protection board. When the battery voltage gradually rises during charging and exceeds the safety threshold, the protection board immediately activates its protection mechanism. Typically, a lithium battery cell has a rated voltage of 3.7 volts and a charge cutoff voltage of 4.2 volts. If the charging voltage exceeds 4.25 volts, it may enter an overcharge state. The protection board integrates a high-precision voltage detection circuit that monitors the voltage changes of each cell in real time. Once the voltage of a cell reaches the preset overcharge protection point, the control chip responds quickly.Once the protection board's control chip recognizes the overcharge signal, it immediately shuts off the charging circuit. This process is achieved by driving the MOSFET in the protection circuit. During normal charging, the MOSFET is on, allowing current to flow smoothly into the battery. When overcharging occurs, the control chip outputs a signal to shut off the charging MOSFET, thereby blocking the external charging power supply from supplying power to the battery. At this point, even if the charger is still operating, current cannot flow into the battery, effectively preventing further voltage increases.To ensure reliable protection, overcharge protection typically has two thresholds. The first level is the overcharge detection voltage, typically set between 4.25 and 4.35 volts, which, when triggered, shuts off the charging path. The second level is the overcharge release voltage. This means that the protection board will only allow charging to resume when the battery voltage naturally drops to a safe value (such as 4.15 volts) due to self-discharge or load use, thus avoiding frequent false trips. This design ensures both safety and system stability.Furthermore, lithium battery protection boards typically employ multi-cell monitoring. Especially in series-connected battery packs, the voltage of each cell must be independently monitored. Because of slight variations between individual cells in a battery pack, voltage imbalances can occur over time. The protection board not only provides overcharge protection but also integrates a balancing circuit that diverts current to cells with higher voltages during charging, allowing them to charge synchronously with other cells, thus preventing damage to individual cells due to overcharging.It is worth noting that overcharge protection does not operate in isolation; rather, it works in conjunction with over-discharge protection, overcurrent protection, and short-circuit protection to form a complete battery safety management system. These functions are integrated on the protection board, and through sophisticated circuit design and algorithm control, they enable comprehensive, real-time monitoring and protection of the battery.In summary, the lithium battery protection board effectively prevents overvoltages caused by overcharging through precise voltage detection, fast MOSFET switching control, and a multi-level protection mechanism. This not only extends the battery life but also fundamentally ensures user safety.
