I needed a small single cell LiPo charger and 3.3V buck booster for my IoT stuff.
A small footprint and multi purpose for different size of LiPo cells
SPEC: (well Chinese ebay parts so don't max it out)
Input voltage- 4.5V-5.5V
Full charge voltage- 4.2V.
Charge current 1A - 130mA (adjustable)
Output voltage 3.3V +-5%
Efficiency 61%-85% (Haven't tested it yet)
1pcs 10K Potentiometer multi-turn precision 3296W-103 (preferred a linear one but logarithmic works as well)
2cm thin wire and for those that does not know about International standards 1" AGW 22 will work just fine
Hot glue gun
Some skills ;-)
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Step 1: Collect Your Items and Modify Them to Fit Together
Start with bending the legs on the Buck Booster.
The legs that need to be bend upright are Vin and the third leg GND.
The spacing does not match so make knees as shown in the picture
Assure that the legs fit and match the battery charger solder holes.
The pin out is
Buck Boooster/Battery charger
Vin ------------------------ B+
GND ---------------------- B-
Step 2: Hot Glue the Parts Together
Start with the Buck Booster
Add glue where the drossel meets up with the Charger board, but be careful not to add glue where the potentiometer will rest on the charger board.
Add pressure and check that the Buck Booster and Charger board are aligned.
When the glue has harden hot glue the potentiometer tight to the Buck Booster board side and tight to the charger board to make it a stable and close fit.
Step 3: Make the TinyLiPoCharger Buck Booster Ready for Soldering
Bend the outer leg of the potentiometer to the almost matching negative pole (-) on the Charger board
Now you board should look like this. If not, well you honestly has some lack of skills ;-)
Step 4: Desolder R3 for Charging Current Adjustment
We must desolder the R3 resistor from the charger board. This resistor set the charging current and we will replace it with our potentiometer so that we can adjust the current from 1A to 130mA
Step 5: Soldering It All Together
Solder a thin wire to the wiper leg of the potentiometer (the one in the center)
Bend the the wire over to the component side of the Charger board and solder it to the R3 left side solder pad
Solder the terminal end of the resistor at the (-) negative input on the Charger board
Solder the battery B+ and B- pins on the Charger Board
Step 6: Almost There
After soldering the module is almost ready to use
Don't even think about using it before you have set the CHARGING CURRENT !!!!!
Use the multimeter to adjust the charging current
By adjusting the resistance on the potentiometer measured over (-) on the Charger board and the wire soldered to R3 the charging current can be adjusted to a matching value for your LiPo cell.
As a rule of thumb is to never charge LiPo over there C value. Go low!
Well I have seen them burn due bad Chinese "happy numbers" as in a 5000mA/h 18650 battery ! that's more energy than a cap.
Do not trim the potentiometer out off the TP4056 chip range
The LiPo battery is connected to B- negative and B+ positive
Drive your IoT or other 3.3V device with GND negative and Vo positive