Apple PowerBook (500 Series) - Manual (Page 53)

IMPORTANT Recharge depleted batteries as soon as possible. Leaving depleted
batteries in the computer for longer than 2 weeks (especially in a hot location,
such as the trunk of a car) may damage the batteries so that they can’t
be recharged. If this happens, you need to replace the batteries.
Recharging the batteries
To recharge the batteries in your computer, plug in the power adapter. (Do not
use a recharger designed for another PowerBook model. PowerBook 500
Series batteries must be charged inside the computer.)
A lightning bolt icon appears in the battery monitor module in the Control
Strip when the power adapter is plugged in and a battery is recharging.
The batteries are recharged regardless of whether you are using the computer,
or the computer is off or in sleep. When the computer is shut down or in
sleep, both batteries are charged at the same time, in 2–3 hours. When you’re
using the computer, one battery is charged at a time, and it takes 4–6 hours to
charge both.
Power adapter port
47 Power Management