While travelling charging of mobile battery is great problem because
power supply source is not generally accessible. Here is a simple
project using very common electronics components for charging mobile
battery using AA cells.
Circuit descriptions of mobile cellphone charger
The main part of the circuit mobile cellphone charger is timer IC NE555, used to charge and monitor the voltage level. IC1 get control voltage to pin 5 by zener diode ZD1. Threshold pin 6 and trigger pin 2 is supplied with a voltage set by VR1 and VR2 respectively. The trigger pin 2 of IC1 is below 1/3VCC when discharge battery is connected to the circuit as a result flip-flop of IC1 is switched on to take output pin 3 high. The process is reversed when battery is fully charged of charged battery is connected. Here transistor T1 used to enhance the charging current from output pin 3 of IC1. Adjust potentiometer VR1 and VR2 as per require.LED status for different charging conditions
| Load across the output | Output frequency (at pin 3) | LED1 |
| No battery connected | 765 kHz | On |
| Charging battery | 4.5 Hz | Blink |
| Fully charged battery | 0 | Off |
PARTS LIST
Resistors (all ¼-watt, ± 5% Carbon)
R1 = 390 Ω
R2 = 680 Ω
R3 = 39 Ω/1W
R4 = 27 KΩ
R5 = 47 KΩ
R6 = 3.3 KΩ
R7 = 100 Ω/1W
VR1, VR2 = 20 KΩ
Capacitors
C1 = 0.001 µF (ceramic disc)
C2 = 0.01 µF (ceramic disc)
C3 = 4.7 µF/25V (Electrolytic )
Semiconductors
IC1 = NE555 timer IC
T1 = SL100
ZD1 = 5.6 V/1W
LED1
Miscellaneous
SW1 = On/off switch
1.5V*8 AA cells
Mobile connector