Without the battery, the Powerbook 520 will be unable to turn on without external power. Installing the battery is a relatively easy procedure, but is important to understand how to do so.
If battery is determined to be dysfunctional, a replacement is necessary.
First, remove battery from the battery slot located at the bottom right or left side of the base of the computer.
Obtain a new or refurbished Powerbook Intelligent Battery with Model Number: M1906.
Insert new battery into battery slot. Note: You should hear a click to know the battery is inserted properly.