After Sales
Technical Documentation
RAE/RAK–1N
Accessories
Page 11
Original, 08/96
Small resistor R112 is put to make this little voltage difference in main
current path. Voltage gain over R112 is 83 in the amplifier. This is
compared to two reference voltages. First determines the current at
which LED color is changed: 65mA. Second reference is put for stopping
the charge at lower current value: 30mA. This is made to ensure that
there is no capacity loss in Li–Ion battery if it remains in desktop charger
many days.
Different Charging Voltages
Two cell Lithium–Ion carbon technology requires 8.4V constant voltage
charging. Two cell Lithium–Ion graphite technology must be charged by
8.2V constant voltage. Because the controller is already set to 8.4V
charging, higher voltage reference and voltage dividor from reference to
battery voltage is required to feed 8.4V to controller and maintain 8.2V in
battery line for graphite batteries. Because the reference is zener, its
voltage is not stable unless current is set high enough. Voltage tolerance
of charger sets minimum current value at this voltage: 10V. Nominal
charger voltage makes zener current high. This also makes high leakage
current path from battery to regulator input. V148 is cutting this current
path when either charger or battery is disconnected. Battery chemistry is
detected by battery type sense resistor which is connected to ground
inside battery pack. Connecting battery biases pin 5 of N110 so that
either voltage is selected when charging starts. V147 controls the voltage
shown to charge controller N115. If V147 conducts battery voltage is
directly fed to controller resulting 8.4V charging. If V147 is off, voltage
dividor makes battery voltage 8.2V.
DC Characteristics
Table 1. Battery type sense resistor values inside battery pack
Notes Typical / Nominal
Operating input voltage: 12 Vdc 1V
Max. input current: 800 mA 70 mA
Charge voltage (type sense resistor: 100k) 8.4 V
Charge voltage (type sense resistor: 68k) 8.2 V
Typical power consumption 10 mA
Table 2. Supply Voltages and Power Consumption
Notes Typical / Nominal
Operating input voltage: 12 Vdc 1V
Max. input current: 800mA 70mA
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