Should I try to use this in a solar charging system?
It’s hard to say, because every solar charging system is different and will have a unique power budget. On the Powercell, you could attach a solar cell (like the ones we sell) to the input on the MCP, but the system would only charge if the solar cell’s loaded voltage is above 3.75V. If your system only draws power for short periods of time (e.g. on for a minute a day) and your solar cell gets good sun, the Powercell should work well. But if you have much tighter power constraints then you need to boost the efficiency and use something other than the MCP charger. However the TPS regulator on the Powercell is great for low power applications since it has a low quiescent current and can take input voltages as low as 0.3V and boost it to 3.3/5V. Hopefully we’ll get some more documentation on this subject soon.