1.COMPATIBLE MODELS: Li ion battery replacement parts, fit for V7 V8 vacuum cleaners, easy installation and removal, long service life. 2.BATTERY PROTECTION: It adopts integrated microchip, which has the function of preventing overcharge, overdischarge and overcurrent. 3.HIGH SAFETY: Provide short circuit protection and voltage stabilization circuit, effectively prolong battery life, safer and more reliable. 4.BATTERY CHARACTERISTICS: 4000mah polymer li ion battery, voltage is 21.6V, high capacity battery provides long lasting performance and durability. 5.PERFECT REPLACEMENT: Just take out the internal power battery of the vacuum cleaner and install a new power source to improve work efficiency.