Shimano di2 battery charger usb connection sm bcr2 di2 charger for the internal battery that will keep your di2 system shifting di2 uses a powerful long life 74v li ion battery keep it in top condition and ready for shifting with this specific shimano di2 charger 15 hour charge time plugs in directly to the sm ew90 handlebar junction a can also be used for completing firmware updates when linked to e tube software on your pc