Mobile cellphone charger

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)


No battery connected

765 kHz


Charging battery

4.5 Hz


Fully charged battery




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


C1 = 0.001 µF (ceramic disc)

C2 = 0.01 µF (ceramic disc)

C3 = 4.7 µF/25V (Electrolytic )


IC1 = NE555 timer IC

T1 = SL100 or any Medium power general purpose NPN transistor like: 2N4922 , 2N4921,2N4238, FCX1053A

ZD1 = 5.6 V/1W



SW1 = On/off switch

1.5V*8 AA cells

Mobile connector

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