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Simple LM317 Solar Charger

A simple solar charger for 12V batteries to keep them topped up and based on the LM317. View the post explaining the circuit here.

PCB board: 17.35mm x 11.2mm
Input Voltage: 16V to 20V
Input current rating: Up to 80mA
Output voltage (no load): 13.65-14.1V (ideally 13.7V)
Output voltage (2mA load): 13.35-13.85V
Output voltage (10mA load): 13.25-13.75V
Output voltage (50mA load): 13-13.45V


v1.0 (23 June 2012) – Download
– Initial Release

Build your own

Parts Required
LM317 TO-92 (1) – LM317LZ – [Q1] 240 Ohm Resistor 1/4W 1% (1) – [R1] 2.43K Resistor 1/4W 1% (1) – [R2] Schottky Diode DO-35 (1) – BAT42 – [D1] Female headers (2)


PCB Guide

PCB Ready for etching


Creative Commons License
This work is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported License.

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