Ultra-Low Power LiPo Charger via Energy Harvesting from a Solar Cell
What is it?
This is a small (0.5 x 0.5 inch) breakout board for Texas Instrument’s BQ25504Ultra Low Power Boost Converter with Battery Management for Energy Harvesting Applications.
From the datasheet: “The bq25504 device is the first of a new family of intelligent integrated energy harvesting nano-power management solutions that are well suited for meeting the special needs of ultra low power applications. The device is specifically designed to efficiently acquire and manage the microwatts (µW) to milliwatts (mW) of power generated from a variety of DC sources like photovoltaic (solar) or thermal electric generators. The bq25504 is the first device of its kind to implement a highly efficient boost converter/charger targeted toward products and systems, such as wireless sensor networks (WSNs) which have stringent power and operational demands. The design of the bq25504 starts with a DC-DC boost converter/charger that requires only microwatts of power to begin operating.”
The BQ25504 is a high-efficiency boost converter of great flexibility that can be used to charge a battery using energy harvesting from a variety of sources. Here I have chosen to set the parameters of the boost converter to charge a standard one-cell, 4.2 V LiPo battery like this one. The BQ25504 employs a Maximum Power Point Tracking (MPPT) method which regulates the input impedance of the charger to maintain maximum efficiency of the solar cell. I have set the MPPT to 78% of the open-circuit voltage of the solar cell.
for more detail: BQ25504 Solar Cell LiPo Charger