Main components

chip:

XX4056 model 1A lithium battery linear charging chip, basically any brand will work. I used two WINSOK WSP4056s and two unbranded 4056s I bought on Taobao, so I can see which one lasts longer.

Battery Holder:

Taobao product, 4-section pin 18650 , 4.25 yuan. There is a problem with the pin size on the details page. The store did not correct it after feedback. Several stores have this problem, and the PCB package has been modified.

The two batteries in the middle are difficult to remove. If you have any tips, please share them in the comments section.

Part of the circuit

Schematic:

The switch here can switch between 1A and 500mA charging current. When the switch is set to 4-5, it will short-circuit both ends of R1. The resistance of PROG to ground is 1.2K and 1A charging.

When the switch is set to 5-6, the resistance of PROG to ground is 2.4K and charging is 500mA.

CC foot pulls 5.1K, you can request 5V voltage from PD protocol charger

VCC from 5V to 4056 is connected in series with 0.25 ohm 1206 package 1/4W, which can share a little heat at 1A, reduce chip heating, and avoid reducing charging current.

PCB:

Because it is all hand soldered, the heat dissipation GND on the bottom of the 4056 chip refers to the manual, and four 1.2mm holes are made, and there is no solder mask green oil on the bottom to facilitate soldering.

test

Without powering on, first measure whether the resistance of the PROG pin to ground is the set value and whether the switch is working.

After powering on, measure the input voltage (5V) and the voltage at both ends of the battery holder (about 4.2V), and the light will turn green.

Plug in the battery, the light will turn red, and it can be charged normally.

episode

BAT is short-circuited to GND, and the current is about 120mA, which is similar to the charging current below 3V in the manual. However, the WINSOK indicator light is on red, and the Taobao non-brand indicator light is all off.