I've recently been looking into the possibility of using an amorphous silicon solar cell (like they have in calculators) to supplement my very low power BLE system's current consumption to extend the life.
I've found some cells that can provide 10-20uA of current during daytime (indoors). Since my system is mostly in a low power state, this power supplement is enough to offset some of the total power consumption and greatly extend the battery life.
The voltage supply required for my system can be anywhere between 2.4v and 3v, but probably needs a battery capacity of >750mAh to keep it alive for as long as it needs to be. What would be the best battery chemistry to use in this scenario? And what is the most efficient way to charge the battery(s) while keeping cost to a minimum?
(I've found a solar cell supplier that does a variety of voltages, so that shouldn't be an issue)