# Charging a Li-Ion battery with a photovoltaic cell during constant current phase

I have a 3.7V, ~1500mAh Li-Ion battery that I am planning to charge with a small photovoltaic cell that will output roughly 100mA when under full sunlight. As I understand it, a Li-ion battery should be charged at a constant current of about 0.5C until its voltage has reached 4.2V, at which point it should be charged at a constant voltage. (I realize fully charging this battery will take 15+ hours)

My question is what will be the effects on battery life if this battery is being charged at 100mA/1500mA = 0.067C during the constant current phase? Keep in mind that the PV cell will not always be under full sunlight, meaning the output current will fall below 100mA and vary. Follow up question: will variations at low (<.067C) charging rates during the constant current phase cause substantial harm?

• At this low rate you can limit the Vf to 3.9V for less aging if you leave it on without an auto shutoff. Mar 11, 2017 at 19:23
• I would suggest limiting that voltage to 4.1V at least for having the advantage of the full capacity, see electronics.stackexchange.com/q/482791/20285 Mar 14, 2020 at 22:52