The thinkpad battery 44 uses advanced lithium ion technology to create an efficient power source for the x230 and x220 systems these are compatible with the x220 and x230 systems and are ideal for use as a replacement or spare the 6 cell batteries are rechargeable and allow you to stay unplugged for longer lasting an average of 63 watt hours however they are not compatible with the thinkpad external battery charger 40y7625 many factors cause battery life to differ these include po