https://purengom.com/2010/07/09/iphone-battery-%ea%b5%90%ec%b2%b4-%ed%94%84%eb%a1%9c%ea%b7%b8%eb%9e%a8%ec%97%90-%eb%8c%80%ed%95%b4-kt%ec%99%80-%ed%86%b5%ed%99%94/