As a result of a faulty protection circuit or a malfunctioning detecting cabinet, the charging voltage will exceed 5V, resulting in electrolyte dissolution, a violent reaction within the battery, and a quick rise in battery internal pressure. When the battery reaches a certain point, it will explode. During ultrasonic welding, intense energy is used to melt the inside diaphragm of the battery, causing the positive and negative electrodes to short-circuit and explode.