Epson PX-8 Technical Manual page 38

REV.-A
Fig. 2-8 illustrates the main battery charging operation from a low voltage. The individual steps of
the operation
CD
through (J) are explained in detail in the following:
CD
Situation - Low voltage is detected while the computer is used with the AC adaptor connect-
ed.
The charging control is enable, and the battery is charged during normal computer use for
aperiod of 11 hours. During that time, the battery may not be fully, charged depending on the
particular use of the computer. After 11 hours, the charge mode changes to trickle charge in
which the battery is charged at a current of approximately 40 mA. The figure shows a charg-
ing current of more than 40 mA, indicating that the battery is being discharged.
CD
Situation - The battery voltage falls to 5.0V while the computer is used.
Since the AC adaptor remains connected, the charge mode is switched back from trickle to
normal charge. Sub-CPU 7508 always monitors the battery voltage using an AID converter
and, whenever it detects that the voltage has fallen to 5.0V or below, it automatically switches
the mode through port 41. The circuit restores the same charging operation as
CD
above. The
almost linear changes during the normal and trickle charges indicate that the charge and dis-
charge currents remain almost constant during these durations.
<l)
Situation - After the AC adapter is disconnected, the computer is used for a while, and then
power is turned off.
While the computer is used, the battery power decreases depending on how it is used. After
power off, the battery power decreases for backing up the internal circuits.
CD
Situation - The AC adaptor is connected while the power remains off.
The eight-hour normal charge starts when the AC adaptor is connected. However, it is inter-
rupted four hours after when the adaptor is disconnected. The battery is charged at the nor-
mal charge current during this interval regardless of the battery power.
®
Situation - The normal charge is interrupted by replacing the adaptor connection to another
AC line outlet.
®
Situation - The adaptor is reconnected and the normal charge is resumed.
The eight-hour normal charge starts again when the AC adaptor is reconnected.
Note 1: The main battery charging is controlled by detecting connection of the AC adaptor, re-
gardless of the current residual battery power or the past charging operations. The 8- or
11-hour normal charge starts depending on whether power has been turned on or off
when the adaptor is connected.
Note 2: The battery may not be fully charged even though the adaptor is left connected for a long
period of time. It is highly likely that the battery will remain below the full charge, espe-
cially when high power consuming operations are being performed while the battery
charge is in process.
When charging control is disabled
When the charging control feature is disabled, the battery is charged at the normal charge current
as long as the AC adaptor is connected. Leaving the adaptor connected for a long time (over-
charging the battery) may affect the life of the battery.
2-14