Charges in two stages
1 - Quick charge, charges with almost constant current untill 4V, red light
2 - precise charge, charges with decreased current untill 4.2V. green light
This will not overcharge your batterry so you dont have to worry about time. Commercial chargers work like this. At beginnig of 2nd stage battery is charged at about 90% of its capacity.
v1.1 - one op amp used
