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. IC 1 get control voltage to pin 5 by zener diode ZD 1 . Threshold pin 6 and trigger pin 2 is supplied with a voltage set by VR 1 and VR 2 respectively. The trigger pin 2 of IC 1 is below 1/3V CC when discharge battery is connected to the circuit as a result flip-flop of IC 1 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 T 1 used to enhance the charging current from output pin 3 of IC 1 . Adjust potentiometer VR 1 and VR 2 as per require. LED status for different charging conditions Load acr...