The STEVAL-ISV019V1 is an Evaluation Board based on the SPV1050, an Ultra Low Power (ULP) energy harvester and battery charger with embedded MPPT and LDO (Low Dropout) Regulators.
The evaluation board is working at the best efficiency implementing the MPPT (Maximum Power Point Tracking) DC-DC converter configuration.
It is optimized to harvest energy from Photovoltaic (PV) panels supplying 0.5V to 2.5V and 30μA to 20mA. You can charge a battery with 3.7V under-voltage protection threshold and 4.2V end of charge voltage threshold. Operating flexibility is possible for a different PV panel and battery with a few easy board changes on the application components.

First start-up at 500mV input
150mV to 4.25V input working voltage range
4.25V end of charge battery voltage
3.7V battery under-voltage protection

Battery Charging & Monitoring, STMicroelectronics