fx-100MS fx-115MS fx-570MS fx-991MS - Support
support.casio.com › en › manualpower is low. Continued use of the calculator when the battery is low can result in improper operation. Replace the battery as soon as possible when display figures becomes dim. Even if the calculator is operating normally, replace the battery at least once every two years (fx-100MS), or three years (fx-115MS/570MS/991MS).