18650 Li-Ion charger with no chip
(Reverse Engineered Schematics)
Schematic of the 18650 3.7V Li-Ion / Li-Pol battery charger with no chip (no charging control integrated circuit). The switching supply contains only 2 discrete transistors. The charging circuit contains two discrete transistors and a voltage reference 431 (TL431). The nominal charging voltage is 4.20V (I've measured 4.29V). The nominal charging current is 400mA (I've measured 360mA).
Photo of Chinese Li-Ion charger. It has US plug, but the input voltage is universal 100 - 240V.
Circuit board from surface mount (SMD) component side.
PCB board from through hole (THT) component side
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