What if a device could harvest the power of ambient light inside your home in order to charge its battery? What if this power could reduce the frequency of needing to charge the device, if even by a little bit?

We lead research to test just that idea. Limiting our charging surface to approximately 4 sq. inches, and assuming average office light conditions, we designed and tested a series of low-lux charging circuits to charge a 3.7V Lithium Polymer rechargeable battery.

Tests were conducted with 9 different solar cells designed for low-lux charging. Results wer encouraging: under lighting from a single incandescent light bulb (typical office lighting), we were able to achieve approximately 250mWh/month gain under average conditions, or abut 20% of an iPhone's battery capacity.