PWM charger (20A) with USB output

Development Stage Tested prototype, only minor issues left.

This PWM charge controller is cheaper than the MPPT charge controllers, as it does not contain the internal powerful DC/DC converter necessary for MPPT. The lower production cost and easy manufacturing with larger SMD components makes it ideally suited for solar home systems (SHS) for rural electrification.

The design allows to use either SMD MOSFETs or TO220 THT MOSFETs, which can be easily attached to a heat sink.

Charge controller PCB

Features

  • 12V/24V battery voltage
  • 20A max. charge current (10A with cheaper MOSFETs possible)
  • 55V max. solar input
  • 32bit ARM MCU (STM32L072)
  • Expandable via Olimex Universal Extension Connector (UEXT) featuring I2C, Serial and SPI interface (e.g. used for display, WIFI communication, etc.)
  • USB charging (single port)
  • Low-side load switching
  • Built-in protection (yet to be tested):
    • Overvoltage
    • Undervoltage
    • Overcurrent
    • PV short circuit
    • PV reverse polarity (for max. module open circuit voltage of around 40V)
    • Battery reverse polarity

Development

The charge controller is under active development and you are welcome to participate.

Visit the GitHub page for schematics, board layout and firmware.