The device is designed to efficiently extract microwatts (µW) to milliwatts (mW) of power generated from a variety of high output impedance DC sources like photovoltaic (solar) or thermal electric generators (TEG) without collapsing those sources. The battery management features ensure that a rechargeable battery is not overcharged by this extracted power, or depleted beyond safe limits by a system load.

In addition to the highly efficient boosting charger, the bq25570 integrates a highly efficient, nano- power buck converter for providing a second power rail to systems such as wireless sensor networks.

Ultra Low Power DC-DC Boost Charger

• Cold-start Voltage: VIN ≥ 330 mV
• Continuous Energy Harvesting From VIN as low as 100 mV
• Input Voltage Regulation Prevents Collapsing High Impedance Input Sources
• Full Operating Quiescent Current of 488 nA

Energy Storage

• Energy can be Stored to Re-chargeable Li-ion Battery, Super- capacitors or Conventional Capacitors
• Battery Charging and Protection
• Internally Set Undervoltage Level
• User Programmable Overvoltage Levels
• Battery Good Output Flag
• Programmable Threshold and Hysteresis
• Warn Attached Microcontrollers of Pending Loss of Power
• Can be Used to Enable or Disable System Loads
• Programmable Step Down Regulated Output (Buck)
• High Efficiency up to 93%
• Peak Output Current up to 110 mA
• Programmable Maximum Power Point Tracking (MPPT)
• Provides Optimal Energy Extraction From a Variety of Energy Harvesters including Solar Panels, Thermal and Piezo Electric Generators

Input voltage should be kept below 4.2V. Not all input voltage / battery type combinations work well. Some input voltage tweaking might be necessary for optimal results.

Settings calculator link: https://github.com/ceech/BQ25570

Storage On the board there is a LiR2450 socket. There are also two sockets for optional 2.7V super capacitors.

Dimensions of the board are: 38mm x 44mm