BATTERY PACK FOR ELECTRIC TOOL, AND BATTERY CONNECTION DEVICE

A battery connection device is provided with an authentication data creating unit that creates authentication data, a conversion unit that performs a first conversion of the authentication data, a transmission unit that transmits the authentication data to a battery pack, a receiving unit that receives from the battery pack a battery-side conversion result that is data obtained after the authentication data is converted by the battery pack, a reverse conversion unit that, on an assumption that the battery pack creates the battery-side conversion result by performing the first conversion and a second conversion on the authentication data, performs a reverse conversion of the second conversion on the battery-side conversion result, and a determination unit that determines whether or not the battery pack is an authentic product by comparing a result of the reverse conversion with a result of the first conversion.