Specifications:
Discharging current: Max. 2A
Charging current: Max. 1A
Input voltage: 4.5-8V DC
Output voltage: 4.3-27V DC (Continuously adjustable)
Charging voltage: 4.2V DC
Size: 3.3x2.3cm/1.3x0.91"
Package Included: 12pcs 2A USB Adjustable Boost Module

Application:

For example, the VIN + terminal is connected to a 5V solar panel and the BAT + terminal can output 42V to charge a 3.7V 18650 battery.
The OUT+ terminal can output an adjustable voltage. You can adjust as much as you need.
Can be used for multimeter to recharge lithium battery.

Tips:
All the circuits are connected before the battery.
No live operation.
Debug before use, the default output is about 9V.
Input voltage 4.5-8V.
The output voltage is continuously adjustable 4.3-27V.(Above 4.3V and below 27V, any voltage can be output, you can adjust the boost counterclockwise by yourself).
Charging voltage 42V, Charging current Max 1A, Discharge current max 2A.
Output reference maximum current 5V 1.4A, 9V 0.8A, 12V 0.6A.
Quescent current is about 0.5 mA.
Overshoot protection.
Over-discharge protection None (it can also be said to have, 2V cuts off the boost but does not block the output, the output still has 2v).
Cut-off boost 2V, depending on the situation, whether to add a protection board.