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Li-Ion slow pace charger

 
Main project requirements:

  1. The popular TP4056 Li-Ion battery charger charges Li-Ion batteries with currents up to 1A, which can be a high value for low-capacity batteries less than 500mAh (e.g. from e-cigarettes).

  2. It is necessary to be able to charge the batteries with different currents depending on the need: in the original mode with 1A current, 500mA current, and 100mA current.

 
Schematic of the device and finished device.
 
 
Slow pace Li-ion charger schema
TP4056 MiniUSB without protection
TP4056 MicroUSB with protection
Slow pace Li-ion charger
Slow pace Li-ion charger
Slow pace Li-ion charger
How it works and components used in the project.

  1. Li-ion battery charging module based on TP4056 chip contains a 1.2kOhm resistor (digital code 122, this is resistor R3 on the photo of the module with micro USB connector). This resistor sets the charging current of the battery being charged.

  2. This resistor, which is responsible for the charging current, is the only one with this resistance rating on the module board and although it may be located in different places in different versions of the module, it is always located next to the TP4056 chip and has a resistance rating of 1.2kOhm (122).

  3. This 1.2kOhm resistor (122) was unsoldered and instead of it two wires were soldered to its contacts and connected to a separate PCB board.

  4. For convenience, the board was matched to the dimensions of the TP4056 module and fixed above it around the perimeter on 4 copper pieces of 0.75mm wire.

  5. The board has a 3-position DIP switch. All three inputs on one side were soldered together and connected to one of the pins of unsoldered 1.2kOhm resistor (122) on TP4056 module. There are 3 resistors (one of which is a combination of 2 resistors in series) connected to the outputs of the 3 position switch:

    1. The first contact of the switch is connected to 1kOhm and 200Ohm resistors in series to create an analog of the unsoldered 1.2kOhm resistor (122). This will simulate the original 1A current battery charging mode.

    2. The second contact of the switch is connected with a 2kOhm resistor. At this resistance, the battery charge current is 500mA.

    3. The third contact of the switch is connected with a 10kOhm resistor. At this resistance, the battery charge current is 100mA.

  6. The free contacts of the resistors mentioned above are combined and connected to the second contact of the unsoldered resistor "122" on the TP4056 module board.

  7. Thus, by selecting one of the three switch positions, the user decides which resistor to use and therefore determines the battery charging current.

  8. For the convenience of connecting the battery, the contacts of the TP4056 charging module were brought upwards (through a support wire) and wires with alligator clips were connected to them.

  9. Be careful to select and include only one resistor in the circuit. Connecting several resistors at the same time will lead to parallel current flow and the total resistance will be low, which may lead to incorrect operation of the TP4056 chip.

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You can find a list of used components in this project with references in the Google-document ("Slow pace Li-ion charger" sheet).

 
 
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