Just like regular watches need batteries to constantly maintain time, the computer's internal clock also needs a constant power source. In addition, many older laptops use CMOS batteries to power the memory chip, which stores configuration settings like boot priority from a specific media, power saving mode, memory. There are several signs by which you can easily determine that there is no power or if your battery will run out of power soon. Different laptops may have different symptoms and this is based on the manufacturer's. The location of the battery on the motherboard may vary depending on the manufacturer of the device, but it is almost always easy to visually identify it due to its shape and color. A typical. Before buying a new battery, remove your original battery and look for the part number. Buying a replacement with a matching part number guarantees a 100% fit. Most CMOS batteries. Buying a new CMOS battery can be tricky because laptops use different connectors, voltage, polarity, wire length, and battery size. Most laptops have a single-use CR2032 battery but on.