User Guide

After Sales
Technical Documentation
Handsfree Desktop Charger CHH–7
Original, 11/94 Page 13
Charge States and Charge Control
Charge current for the phone is supplied through a series connected
switching transistor located in the phone. When this transistor is on, the
charger is supplying a constant current to the phone. This is the rapid
charge mode.
When the transistor is off, no current is supplied to the phone and the
charger is in the constant voltage mode.
Having been charged up in the rapid charge mode, the battery is kept fully
charged by using pulsed charging, ie. switching power alternately on and
off at a variable duty cycle and a frequency of a few Hz.
The desktop charger also contains control logic for spare battery charging,
which is enabled when no phone is connected or when the phone is in the
pulsed charge mode. When the phone is in pulse charge mode the spare
battery can only be charged at 70% of the rate when no phone is present.
Charge Indication to User
The desktop charger has dual–colour LEDs to indicate the charge state of
the phone and the spare battery, the right hand LED is for the phone and
the left hand LED is for the spare battery. The LEDs are off when there is
no phone or spare battery connected.
Right LED for phone:
Red phone LED indicates that the phone battery is being charged in fast
charge mode or charging is disabled due to battery temperature being
outside permissible range.
Green phone LED indicates that the phone battery is full and that trickle
charge mode is active.
Left LED for spare battery:
Red spare battery LED indicates that the battery is not full; either there is
a fast charge mode active or charging is disabled due to a battery
temperature ’fault’ or the phone is being fast charged.
Green spare battery LED indicates that the battery is fully charged.
Flashing red spare battery LED indicates that a discharge cycle is active.
The liquid–crystal display of the phone also contains a three–bar battery
charge display. ”Charging sequence active” (state A) is indicated by the
bars illuminated sequentially, starting from the bottom bar (each bar is on
for a period of 1 s).
”Battery full” (state B) is indicated by all three bars steadily illuminated.