simple & safe charger for 4.2V Li-Ion battery. Use at own risk in safe place. Only diodes used.

Diodes used: 10A10 (10Amp) one piece; 1N5822 (3Amp) schottky diode two pieces. All in series with 5V mobile charger (5.15V) with amperage less than 3A. Charged 18650 cell to to 4.10V after overnight, 4.23V after one day, 4.34V after two days.
Other diodes tried were 2x10A10 in series and 2xRL207 in series but both charged to 4.0 V after overnight charging.

[@sal3011]

Hey.. Salman here.. Where are you!