live battery voltage monitor

[rahol]

hello frnds

i want to make live battery voltage indicator cum monitor. i have tried two circuits as shown in below pics. i just wanted is that one green led should illuminate when battery is fully charged.

main purpose of my project is : while charging ,if charging battery voltage exceed certain defined voltage point say 11.5 V (FOR 11.1 V BATTERY) one green led should illuminate to indicate battery is fully charged now???





NEED HELP !!

Is my circuit is correct ? if not then plz suggest some other logic or ckt if u have any????

 

[Audioguru]

11.1V sounds like a 3-cells Lithium battery. It is usually charged by a Lithium battery charger IC that limits the current, charges to 12.60V, monitors the charging current then turns off when the charging current drops low.

At only 11.5V then it is only about half charged. When the charging voltage reaches 12.6V it is about 70% charged.
when its voltage drops to about 9.6V then its load should be disconnected and it should be charged.

Your circuit does not limit the current, does not accurately limit the voltage and does not turn off when the charging current drops low.

EDIT: The 3 cells must be balanced so they are charged separately to 4.20V each.

 

[rahol]

can you suggest me some other circuit

i dont want charging circuit , i want indicator when battery is fully charge

 

[Audioguru]

When the charging circuit senses that the charging current has dropped low and has turned off the charging then IT should light the LED that shows that the battery is fully charged.

When your charging circuit turns off the charging then its current also drops low which can be detected then lights an LED.

I have 2-cell Lithium batteries. The charger charges each cell with limited current to 4.20V each, senses that the charging current has dropped low, turns off the charging then lights a green LED.