hi can any give me the suggestion for designing a circuit that charges battery when the power is present and it automatically stops after charging fully....and it should be discharged only when there is no power....output should be 5V,1amp

 

Hi Nandu,
V/AH rating of the battery is 12v/1.35Ah

 

Lead acid battery

 

So do you have a 12v battery and it gives out 5v to your load, or what?

 

1. What do you mean by "when the power is present"? Does this refer to input power to the charger or when the battery is under load?
2. What does "discharges only under power" mean? Do you mean that the battery disconnects from the load during charging?
3. You tell us that the battery is a 12 volt lead-acid rated at 1.2 Ah. A charging circuit delivering 5 volts cannot charge the battery. The charging voltage must be greater than the peak voltage od a fully charged battery which is around 14 volts.
4. What is the device being powered by the battery?

 

I want to use my internet modem even at the time of power cut.....For that i want to use power from the battery ....At the time of power cut modem is powered with this battery...Modem requires 5V,1amp

 

I suggest looking for a USB battery. A quick internet search will tell you the rest.

 

1. What do you mean by "when the power is present"? Does this refer to input power to the charger or when the battery is under load?
2. What does "discharges only under power" mean? Do you mean that the battery disconnects from the load during charging?
3. You tell us that the battery is a 12 volt lead-acid rated at 1.2 Ah. A charging circuit delivering 5 volts cannot charge the battery. The charging voltage must be greater than the peak voltage od a fully charged battery which is around 14 volts.
4. What is the device being powered by the battery?

I want to use my internet modem even at the time of power cut.....For that i want to use power from the battery ....At the time of power cut modem is powered with this battery...Modem requires 5V,1amp