Some laptops can contain more than one internal battery to power clock, CMOS, resume and sub-battery functions. Type vary from Lithium coin cells to Nickel Cadmium (NiCd) and Nickel Metal Hydride (NiMh) packs. These can be soldered directly to the system board (or sub-card) or attached using a wire harness and sub-minature connector.

Locations of these devices vary from model to model but, in most cases, these devices are found underneath the keyboard. Some manufacturers locate the cells in odd places like underneath a mouse ball, touch pad or in the screen frame housing.

Use extreme caution when removing the keyboard on any laptop! Keyboard assemblies are connected to the system board by flat "ribbon" cables. These cables are usually made from Mylar™ (or similar materials). Cable assemblies can be expensive and very difficult to find, even through an authorized dealer.