Let's say I have a lithium-ion battery like the this one. and let's also say that I have a solar cell like one of the following this or this. i know that charging a lithium io battery is tricky and ideally involves ramping up the voltage at larger amperage followed by a flat voltage and lower amperage If I'm not super concerned with performance, is it possible to simplify the process and trickle charge the battery over a longer period of time? Also, if the voltage output of the solar cell is less than optimal, would that effect the performance of the battery?
LT3652 is one of the best solar charge controller chip for small applications. It has inBuilt MPPT and Programmable Charge Rate Up to 2A with input voltage range of 4.95V to 32V (40V Abs Max)
there is a Sparkfun board called Sunny buddy which uses the same chip. Schematics and layouts are available.
You want to charge a 150 mAh battery using a 20 mA solar cell. A full charge would require more than one day, especially when there are clouds in the sky. But even at a day without clouds, you won't get the 20 mA from sunrise to sunset, when the solar cell is optimal aligned to the sun at noon. In the night the battery should not discharge thru the solar cell, you should insert at least a diode between both.