For another project I wanted to use a Li-Ion or Li-Po battery charger and controller that gave a 3V3 and 5V output. The power demands were not high. After searching the internet a few days I did not found any controller that fit my demands: USB connector, small form factor, stay on even when very low current is drawn from the battery.
I tried to combine a 5V controller and charger and combine it with a 3V3 regulator. This did not work when the battery was empty, the power switched on and off before it became stable.
So I designed and made my own:
The size is 26.5 x 20.2 mm. Maximum power output is about 500mA. This is not checked yet, I use it for low power applications. Charge current is 500mA max. Output voltage 5.1V and 3V3. LED will signal when battery is fully charged. You can connect a 3.7V Li-Ion or better a 3.7V Li-Po cell with charge and discharge protection.
The unloading of a Li-Ion 3.7V cell will NOT stop with this controller when the battery voltage is below 3.0V. You HAVE to use another circuit to protect a 18650 Li-Ion cell. I have now a good experience with a Li-Po cell with protection module:
Building and Costs
I have designed and ordered the PCB at JLCPCB. I used LCSC parts in my design and ordered these parts separate. I soldered the components myself on this PCB using a heat gun and solder paste. I did not use a solder mask.
Cost of PCB: $5.00, Shipping cost: $ 11.79, total cost $ 16.79 for 10 PCB’s. So total about $1.68 per PCB.
Cost of Parts: $ 10.53, Handling cost: $3.00, Shipping cost: $ 8.91: Total cost $ 22.44 for building 5 controllers. So total about $ 4.50 per controller.
Total cost: about $ 6.20 (at writing € 5,15) per controller. Soldering is done by myself.
The schematic, PCB design and BOM are shared at
Charger via Micro USB connector
MCP73831: Miniature Single-Cell, Fully Integrated Li-Ion, Li-Polymer Charge Management Controller
- Thermal Regulation
- Package used: SOT-23
- Programmable Charge Current set to 500mA
- Reverse Discharge Protection
- Charge Complete Mode: No Charge Current: Status = HIGH
3V3 output direct from battery voltage, max 250mA
MCP1700: Low Quiescent Current LDO Voltage regulator
- 1.6 μA Typical Quiescent Current
- 250 mA Output Current for Output
- Low Dropout (LDO) Voltage: 178 mV
- Short Circuit Protection
- Overtemperature Protection
- Package used: 3-Pin SOT-23
5.2V output from Boost Converter, max 250mA
TPS61041: Low-Power DC-DC Boost Converter
- 1.8V to 6V Input Voltage Range
- 250 mA Internal Switch Current
- 28-μA Typical No-Load Quiescent Current
- Thermal Shutdown
- Overload protection (250mA cut off)