Created by
Created July 12, 2013
Last modified July 14, 2013
Tags joule-thief   led   lighting  


A novel circuit to charge a Li-ion battery from a 2v Solar cell


This circuit maximizes the output from a garden-light solar cell to charge a 3.7v Lithium-ion cell (or 3 NiMH cell in series).

Q3 switches the light on after dark and also acts as an over-charge safety by switching the LED on when the battery reaches full charge.

NOTE: The reversed polarities for the Solar cell and the Capacitor C1 is NOT a misprint! The circuit uses L1 to invert the polarity and boost the input to charge the Lithium cell.


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