The DS1402D-DR8 is a 1-Wire network cable and does not have a battery built into it. Many iButton devices, such as the iButton data loggers that log temperature and/or humidity readings, have an integrated battery. These are commonly used in conjunction with 1-Wire network cables. Keep in mind that several iButton devices do not require batteries to function. They are parasitically powered by the actual 1-Wire I/O line, and the power for this comes from the 1-Wire master (which, for the case of a PC, is either the DS9490R# USB or DS9481R-3C7 serial 1-Wire adapters).
