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 1/3V_CC 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

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

ZD₁ = 5.6 V/1W

LED₁

Miscellaneous

SW₁ = On/off switch

1.5V*8 AA cells

Mobile connector