General; Charging The Phone; Charging The Spare Battery - Benefon DELTA TDP-40-TN2 Service Manual

7.3.1 General

The desktop charger is designed for charging NiCd or NiMH batteries when con-
nected to either a lighter socket charger or a 220 V mains charger. The desktop
charger has two units. The first unit is for the phone, and the second is for a reserve
battery pack. The additional battery pack can also be discharged to improve its per-
formance. The battery capacity and type are read from the memory within the bat-
tery pack before charging commences. If the battery memory is missing, empty, or
faulty, the charger will use the default values stored in the processor EEPROM.

7.3.2 Charging the phone

The desktop charger detects the phone by measuring a voltage in the VBAT line
voltage split. The charging process for the phone is such that the phone controls the
desktop charger processor, which in turn controls the charger connected to the
holder (lighter socket or mains). If the reserve battery pack is also being charged,
then the desktop charger splits the charging current between the phone and the bat-
tery. The phone is always assured of its required current (max. 1500 mA).
7.3.2.1 Discharging the phone battery
The phone indicates discharge state to the desktop charger by a control voltage
below 4.0 V. The charger will not then supply any current to the phone, and a red led
is illuminated in the phone charging indicator. The charger takes no other part in the
discharging process.

7.3.3 Charging the spare battery

The spare battery charging process has three phases: quick charge, continuous
charge, and stand-by charge. The charging sequence starts with quick-charge, and
ends with stand-by charging. The sequence is re-started only if there is a break in
the power supply or the battery is removed from its holder. Accidental shorting of the
charger contacts is prevented by the charging current being supplied to the contacts
after the battery has been in the holder for approx. 1s. Battery recognition is done
with the NTC line. During charging, the desktop charger updates the charge-indica-
tor counter in the battery-pack memory.
7.3.3.1 Quick-charge
The battery is detected in its holder when the A/D converter value is below 162
(U = 3.32 V). This corresponds to an NTC resitance value of 181 kohm, i.e. -20 C
temperature.
Quick charge only functions if the temperature is +10...+40 (A/D 75...28;
U = 1,46...0,55 and NTC resistance 41,8...12,2 kohm). Charging is accomplished by
directing the charger to give a 1500 mA current. The current is split by the switches
Q101 and Q102 in turn, according to the relative requirements of the phone and
XO0244E4_fm5.fm
Product: HPT-40 (Desktop Charger) /
28.1.1999
YO0244
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