The lenovo thinkpad battery 68 is compatible with the w550 t440 t440s l450 t450s t450 t550 x250 and x240 systems this 6 cell battery utilises lithium ion technology and allows you to stay unplugged for longer providing the longest possible battery life the battery can provide power for approximately 72 watt hours and is rechargeable a safe flow of power is ensured by the over discharge protection which prevents damage due to incorrect voltage each one is safeguarded with a chip tha