The power bank's overcharge and over-discharge protection ensures safe charging. Its core function is a coordinated mechanism of "real-time monitoring - precise intervention - multiple protections." This mechanism tracks voltage and current changes during charging and discharging, quickly shutting down the circuit when parameters exceed safe ranges. This not only protects the power bank's own cells from damage due to overcharge and over-discharge, but also prevents external devices from malfunctioning due to abnormal power supply, eliminating safety risks such as overheating, bulging, and short circuits at the source. In an overcharge state, if a cell continuously receives a charge exceeding its capacity, excessive internal chemical reactions can cause heat buildup, leading to bulging or even more serious problems. In an over-discharge state, excessively low cell voltage can damage the internal electrode structure, causing permanent capacity degradation and even the risk of leakage during subsequent charging. Therefore, the protection function must address both scenarios, providing full-cycle safety protection.
The overcharge protection function uses dual voltage and current monitoring to precisely control the charge termination point, preventing overcharging of the cell. The power bank's internal protection module monitors the battery cell's voltage in real time. When a cell reaches saturation (i.e., the voltage reaches the safe upper limit), the module immediately triggers a switch (such as a MOSFET) to cut off the charging path, preventing further external power supply to the cell. The protection module also monitors the charging current. If the charging current suddenly increases due to an external power anomaly (such as a voltage surge), overcurrent protection is activated, even if the cell is not fully saturated, to prevent overcurrent surges and overheating. To protect against overcharging of external devices, the power bank communicates with the device via a charging protocol to identify its rated charging voltage and current, dynamically adjusting output parameters. When the device's battery reaches saturation, the power bank proactively reduces output current until it ceases supplying power, preventing damage to the battery or overloading the motherboard due to continuous power consumption.
Over-discharge protection monitors voltage and load changes during discharge to prevent damage to the battery cell due to excessive discharge and ensure stable power supply. During discharge, the protection module continuously tracks the cell voltage. When the voltage drops to a safe lower limit (i.e., the remaining charge in the cell is nearly depleted), the module shuts off the discharge path and stops supplying power to external devices. This prevents irreversible damage to the cell, such as electrode polarization and electrolyte decomposition, caused by low voltage, thereby extending the cell's lifespan. Furthermore, over-discharge protection monitors the discharge current. If the external device experiences a short circuit or an abnormally high load (such as a sudden current surge caused by an internal circuit fault), the protection module quickly triggers overcurrent protection, shutting off the output to prevent continued high current flow through the cell and device. This prevents overload heating of the power bank and damage to the motherboard, connectors, and other components.
The hardware core of the protection function is a dedicated protection board, whose integrated precision components provide rapid response for safety measures. The voltage detection chip on the protection board samples the cell voltage at an extremely high frequency, ensuring immediate detection of parameter anomalies. Switching elements (such as MOSFETs) feature rapid on/off switching. Upon receiving a protection command, they quickly disconnect the charge/discharge circuit, preventing the abnormal condition from persisting. Some power banks also feature integrated temperature monitoring components on their protection boards. When the battery cell or protection board temperature rises to a safe threshold due to charging or discharging, overtemperature protection is activated. This complements overcharge and over-discharge protection, preventing escalation by shutting down the circuit even in extreme temperature conditions. Furthermore, the protection board's fuse serves as a last resort. If other protection mechanisms fail and excessive current is drawn, the fuse will blow and permanently disconnect the circuit, completely eliminating any potential safety hazards.
Dynamic software algorithm adjustments make overcharge and over-discharge protection more adaptable, meeting the charging and discharging requirements of diverse scenarios. For different cell types (such as lithium polymer and cylindrical cells), the software presets corresponding safe voltage ranges to ensure that protection thresholds precisely match cell characteristics, preventing protection failure or frequent false triggering due to improper threshold settings. When charging multiple devices simultaneously, the software dynamically distributes output current, monitoring the voltage and current of each output channel. If a device shows signs of overcharging (such as a sudden current drop), it will shut down that output channel independently, without affecting the normal charging of other devices. The software also records charge and discharge cycle data. If it detects repeated abnormal voltage fluctuations in a battery cell, it will notify the user of the cell status via an indicator light or the app, helping to proactively mitigate potential risks.
The overcharge and over-discharge protection function also uses a "pre-emptive protection" mechanism to proactively mitigate risks approaching safety thresholds. When charging nears saturation, the protection module gradually reduces the charging current, switching from fast charging mode to trickle charging. This ensures full charging of the battery while preventing continuous high current surges. When the cell voltage approaches the over-discharge threshold, the power bank will flash an indicator light or display the battery level to alert the user of low battery. It will also appropriately reduce output power to prevent sudden power outages and allow the user time to replace the power supply. This progressive protection design avoids the inconvenience of sudden power outages and further reduces the possibility of parameters exceeding the safe range, enhancing the user experience while strengthening safety protection.
The redundant design of multiple protection mechanisms ensures the reliability of the protection function and prevents risks caused by the failure of a single mechanism. In addition to core voltage and current monitoring, some power banks also utilize a dual protection board design. These two protection modules operate independently and cross-check with each other. If one module fails, the other module can still trigger protection normally. Furthermore, the battery cell's inherent safety features (such as explosion-proof valves and high-temperature-resistant casings) also cooperate with the protection function. Even if the protection module fails to respond in a timely manner due to extreme conditions, the cell's physical protection structure can delay or prevent the spread of risk. This multi-layered "software + hardware + physical structure" protection system provides a higher level of fault tolerance for overcharge and over-discharge protection, ensuring the long-term safety of the power bank itself and stable and reliable power supply to external devices in complex usage environments.
