Battery Operation - HP -25 Owner's Handbook Manual

charger connected, the batteries will charge with the calculator
OFF or ON. Normal charging times from fully discharged
battery pack to full charge are:
Calculator OFF: 6 hours
Calculator ON: 17 hours
Shorter charging periods will reduce the operating time you can
expect from a single battery charge. Whether the calculator is
OFF or ON, the HP-25 battery pack is never in danger of be-
coming overcharged.
Note: It is normal for the battery charger/ac adapter to
be warm to the touch when it is plugged into an ac
outlet. It is also normal for the HP-25 calculator itself
to be warm to the touch with the ac adapter/battery
charger connected for battery charging and the HP-25
ON-OFF switch set to OFF.
Battery Operation
To operate the HP-25 from battery power alone, simply turn the
calculator OFF, disconnect the female battery charger plug
from the rear of the calculator, and turn the calculator ON
again. (Even when not connected to the calculator, the battery
charger/ac adapter may be left plugged into the ac outlet.)
Using the HP-25 on battery power gives the calculator full
portability, allowing you to carry it nearly anywhere. A fully
charged battery pack provides approximately 2 to 5 hours of
continuous operation. By turning the power OFF when the
calculator is not in use, the charge on the HP-25 battery pack
should easily last throughout a normal working day.
Most of the battery power consumed by the calculator is used
to light the display, so you can maximize battery operating time
by displaying the minimum number of digits necessary while
calculating. If the HP-25 must be left ON between calculations,
is the display that consumes the least power.