The 6 cell thinkpad battery 75 will greatly extend your devices run time compatible with the e430 e431 e435 e440 e445 e530 e531 e535 e540 and e545 systems it can be used as a replacement or a convenient spare on average the battery lasts for 62 watt hours and can be recharged with the thinkpad battery charger each one utilises efficient lithium ion li ion technology and ensures a safe flow of power with over discharge protection the battery life is affected by many factors