Electrical – LED color changing according to battery charge status


I would like to set up the circuit to charge the 3.7V Li-ion battery using diodes, capacitors,leds,resistors and a zener diode.I have a few questions.
1)The color of the led while the battery is charging:
-Charging: red
-When the charging is complete: green
How do I do that?
2)To charge 3.7V battery, how much DC voltage should I apply to the battery?
Thank you all!
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Best Answer

Use a Li-ION battery charging IC. It is designed to be safe.