Mppt Solar Charge Controller

An MPPT solar charge controller for a caravan. Hardware, Firmware, Webapp for visualization

Hardware main parts:

• Schematic PDF download
• No PCB design so far, just a working prototype on breadboard
• STM32 MCU (bluepill STM32F103)
• SZBK07 DCDC module (LM25116 DCDC driver chip and other electroics removed just power electronic parts used)
• 250W solar panel 36V nominal voltage
• Split charge relay for charging from engine, when driving (separate from this circuit)
• 55Ah and 110Ah 12V leisure batteries in parallel
• 3x ACS712 current sensors
• ADS1115 ADC for current measurement
• FAN for cooling power electronics
• Bluetooth UART module for communnication

Firmware:

• Written in C
• STCubeMX generated base project + user code
• 50Hz controlling loop
• DCDC half bridge controlling via complementary PWM signals
• MPPT tracking, float charging
• simple ASCII UART protocol for communication
• active PWM fan control when power is high

Webapp:

• Python3 based
• Flexx UI
• For visualization and active control of the firmware
• Connection via bluetooth
• Could be running on a raspberry PI

Android app

• There is an initial release of the android app, it is working but not perfect