18650 charger

This design is an 18650 battery charger, using the TP4056 chip. TP4056 is a single-cell lithium-ion battery constant current/constant voltage linear charger. It adopts an ESOP-8L package with a heat sink on the bottom and a simple external application circuit. It is very suitable for portable device applications and is suitable for USB power supply and adapter power supply operation. Internal It adopts anti-reverse charging circuit and does not require external isolation diodes. The charging cut-off voltage of TP4056 is 4.2V, and the charging current can be set through an external resistor. When the charging current drops to 1/10 of the set value, TP4056 will automatically end the charging process. 
The pin functions of the 4056 chip are introduced as follows:
TEMP (PIN1): battery temperature detection input terminal
PROG (PIN2): constant current charging current setting terminal
GND (PIN3): power ground
VCC (PIN4): input voltage positive terminal
BAT (PIN5) :Battery positive connection terminal
STDBY (PIN6): Charging completion indicator terminal
CHRG (PIN7): Charging status indicator terminal
CE (PIN8): The chip can input terminal
is designed with a toggle switch, which can select 0.5A or 1A current charging. Connect a resistor from the PROG pin to GND to set the charging current. The setting resistor and charging current are calculated using the following formula: RPROG=1100V/IBAT