钠电池 PACK 的低压保护系统有什么作用？

What are the functions of low-voltage protection systems for sodium-ion battery PACK?

低压保护监控单体最低放电电压，防止深度过放造成负极 SEI 膜破损永久损伤。放电过程单串电压降至一级预警值，BMS 限制输出功率；跌破二级强制阈值完全切断放电回路。硬碳负极深度放空后 SEI 膜开裂，钠离子不可逆损耗激增，容量永久缩水、内阻持续飙升，整套 PACK 寿命腰斩。低压保护设置两级缓冲机制，先提醒设备降载，极端工况强制停机，离网光伏、户用储能容易深度放电场景阈值适度抬高预留安全余量。搭配均衡系统协同作用，避免单串电芯提前放空拖累整组容量，减少储能设备报废更换频次，延长整套电池包服役周期。

Low-voltage protection monitors the minimum discharge voltage of single cells to prevent permanent damage caused by cracked anode SEI films from deep over-discharge. When single string voltage drops to the first-level early warning value during discharge, BMS limits output power; if falling below the second mandatory threshold, the discharge loop is completely cut off. After hard carbon anodes are fully discharged deeply, SEI films crack with sharply increased irreversible sodium loss, permanently shrinking capacity and continuously rising internal resistance, cutting the whole PACK life in half. Low-voltage protection sets two-stage buffer mechanisms: remind equipment to reduce load first and force shutdown under extreme conditions. The threshold is appropriately raised to reserve safety margin for off-grid photovoltaics and household energy storage prone to deep discharge. Cooperating with balancing systems, it avoids premature full discharge of single cells dragging down the whole pack capacity, reduces scrapping and replacement frequency of energy storage equipment and extends the service cycle of the whole battery pack.