Method:
1. Cut off the mobile phone charger plug. After powering on, use a multimeter to measure the positive and negative wires.
2. The positive wire of the mobile phone charger is soldered to the P+ point of the protection board, and the negative wire is soldered to the P- point of the protection board.
3. Solder two wires respectively to point B+ and point B- of the protection panel. B+ is connected to the positive terminal of the 18650 battery and B- is connected to the negative terminal.
4. With this connection you can charge the 18650.
Materials:
A lithium-ion battery charger (i.e. a general cell phone charger) and a lithium battery protection board.
Note:
The maximum output voltage of the mobile phone charger is 5V, the rated voltage of 18650 is 3.7V, and the cut-off charging voltage is the lithium battery protection board isof 4.2 V, so it can be avoided to some extent.
18650 Battery Overview:
18650 is the creator of lithium-ion batteries - a standard lithium-ion battery model defined by the Japanese company SONY in order to reduce costs, of which 18 indicates a diameter of 18 mm, 65 indicates a length of 65 mm and 0 indicates a cylindrical battery.
Common 18650 batteries are divided into lithium ion batteries and lithium iron phosphate batteries. The rated voltage of lithium ion battery is 3.7V, the charging cutoff voltage is 4.2V, the rated voltage of lithium iron phosphate battery is 3.2V, the cutoff voltage charging is 3.6V, capacity is generally 1200mAh. 3000mAh, common capacity is 2200mAh-2600mAh.