Battery Cap

Sealing function

Prevent the leakage of electrolyte inside the battery and prevent external elements (such as moisture, oxygen) from entering the battery interior, ensuring stable battery performance.

In cylindrical batteries (such as 18650, 21700), the cap and the battery housing are sealed through laser welding or rolling edge processes, forming a closed space.

Safety protection

Explosion-proof valve function: When the internal pressure of the battery is too high (such as overcharging or short circuit causing gas generation), the explosion-proof valve in the cap will rupture, releasing gas to prevent battery explosion.

Overcurrent protection: Some caps are equipped with PTC (positive temperature coefficient thermistor), which causes the resistance to sharply increase when the current is too high, cutting off the circuit to avoid overheating.

Short circuit protection: Through insulation design or additional fuses, prevent direct contact between the positive and negative electrodes of the battery to avoid short circuit.