Solar harvesting into Li-ion battery

The AEMLION is a 0.8×0.6 inch (20x15mm) PCB with the AEM10941 Solar Harvesting IC from E-peas. It efficiently converts solar energy into Li-ion battery charge, it even works with indoor light. It features 3.3V and 1.8V regulated outputs that are enabled when the battery has useful charge and a low battery warning that informs the user of impending shutdown when the battery runs low. It easily integrates into other projects because of small size, castellated via’s, and when soldered onto 0.1″ pitch header it fits in a breadboard.

Solar harvesting into Li-ion battery

I designed it because I took part in the HackadayPrize2018 Power Harvesting challenge with a 1×1 inch Tiny Solar Energy Module and found a lot of interest in selling it. However since most projects have different power demands and people want to choose their own solar panel, I decided to remove the onboard solar cells.

This board is special because it integrates maximum power tracking, Li-ion battery charging and two regulates outputs in a tiny and easy to integrate board. There’s is no other board with so little passive components.

Ideal for indoor applications

The AEM10941 harvesting IC is very suitable for indoor applications because it has an ultra low power startup. The boost converter starts at a very low 380 mV input voltage and 3 uW input power. The IC gets the most power out of the solar cells by doing MPPT maximum power point tracking every 5 seconds.


  • PCB 2 layers (0.8×0.6inch/20x15mm)
  • solar input voltage 50mV to 5V
  • ultra low power startup 380mV/3uW
  • solar input current max 110mA
  • MPPT every 5 secs, MPPT set to 70% (adjustable)
  • Battery: connect your 3.7V Li-Ion battery
  • 3.3V/80mA and 1.8V/20mA regulated outputs. These are enabled when battery voltage is between 3.60V and 4.12V (max charge voltage)
  • battery reverse voltage protection
  • 3.3V status output pin that warns the host MCU if battery voltage drops below 3.60V
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What you get

  • A soldered and tested AEMLION
  • 2x 5pins 0.1″ male headers, you need to solder yourself


  • SRC – solar panel positive terminal, input to the harvesting IC
  • GND – ground
  • STATUS – status output pin, open drain output with 1M pull up to 3.3V, active low. When battery voltage falls below 3.6V it goes low 600ms before the 3.3V and 1.8V outputs are disabled. Can be used to warn the host MCU to gracefully terminate writing to EEPROM/flash and prepare for power outage. Voltage level 0/3.3V.
  • BAT – connects to Li-Ion battery positive terminal
  • 3V3 – regulated output voltage
  • 1V8 – regulated output voltage

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