Phone charging controller (Cut-off)

Hi, I want to make or have equipment to STOP (cut-off) charging while at 4.1V (adjustable). Can anyone advice what I should I do ? I'm new with Arduino. Thanks.

The charging of Lithium batteries is a fairly specialised subject. Generally it's NOT the voltage that tells you when they are charged.

Anyhow, If you want to test the voltage, you simply put the -ve of the battery to the GND of your arduino, and then connect the +ve to any of the analog pins. Then you just do an analogRead to get a value. A fairly simple calculation will then give you the voltage.

Thanks...I thought I can build "stand alone" unit for this purpose.

dealova: Thanks...I thought I can build "stand alone" unit for this purpose.

But DON'T expect this to be a reliable method to detect the charge state of your battery. Also be aware that these things can go BANG in a big way if they're charged incorrectly. People have been killed by these things.