brand new CR2016 rtc battery HEWLETT PACKARD Real Time Clock Battery  P/N 378236-001  for HEWLETT PACKARD / COMPAQ    New cmos bios battery for HP Notebooks. The peformance of a new cmos battery will bring back the power computing to your notebook that has lost it's date/time sequence. This item is the same battery type as the one that's in connected to your HP Notebook where it will be inserted into a small connector that's on the motherboard. This is not the main battery that subs for the AC/DC adapter brick, rather the purpose of this battery is solely for the firmware of the bios chip to maintain date/time clock functions while the notebook is not in use. The cells inside is a new CR2016 so they will provide ample longevity to your notebook