The batteries in my data logger died while in use. Did I lose all of my data?

No. The data is stored on non-volatile EEPROM. For data loggers with external batteries: change batteries and offload data, then relaunch normally. For data loggers with internal batteries: as long as the EEPROM has not been damaged, the data can be retrieved by Onset Computer Corp. Please contact the place of purchase for a return authorization number and request data back service.