Electronic Circuits and electronic circuits, electronic schematics plus an extensive resource for hobbyists, inventors and engineers

DiscoverCircuits.com, has 45,000+ electronic circuits, cross-referenced
into 500+ categories.    We have searched the web to help you find quick design ideas.
We make every effort to link to original material posted by the designer. 
Please let us if you would like us to link to or post your design.

HOME Schematics Index Hobby Corner Dave's Circuits Electronic Resources Contact Info
Imagineering Ezine    Discover Solar Energy Dave Johnson & Associates Faraday Touch Switches

Circuits designed by David Johnson, P.E.
Last Updated on: Monday, December 25, 2017 02:08 PM

List of Dave's Circuit Designs

The contents & graphics of Discovercircuits.com are copyright protected.
LINKING to Dave's circuits is permitted but DO NOT COPY any files to your WEB SITE server

More  Solar Cells

Modified Cheap Solar LED Path Light (May 2, 2014)

Many of the small solar LED path lights on the market today use a single 1.2v NiMH
cell to power a white LED.  The telltale giveaway on these lights is the 4 cell solar panel on top of the light to charge the battery.  Inside these lights, a simple “flyback” voltage converter circuit is used to boost the 1.2v from the NiMH
cell to over 3 volts, to drive one or more white LEDs.  Many of the converter circuits use a propriety IC in conjunction with an inductor.  In one of the lights I bought for a dollar, a 470uH coil was used to produce the needed higher LED voltage. 

I measured the DC battery current drawn from one such light at a low 2ma.  Figuring a conversion efficiency of 80%, that put the 3v LED current at about 700ua. This is a very low LED current.  No wonder these things are not very bright. 

duracell rechargeable 1000mAh 2v 150ma Solar Cell
Duracell rechargeable 1000mAh 2v 150ma solar panel

The battery in the dollar light was an AAA NiMH
cell, with a rating of only 150ma-hour.  I measured the current produced by the 4 cell solar panel on a bright sunny day at a disappointing 35 milliamps.  If you figure that the average sun lit day lasts 6 hours, then the panel would pump only about 210ma-hours of energy into the battery.  Yes, the solar panel would charge the 150ma-hour battery but I wanted a brighter light.

typical solar path light 1 typical solar path light 2 typical solar path light 3 typical solar path light 4
Typical Single NiMH
Cell Solar Lights
Modifiedl solar path light

Modified Solar Light

The first thing I did was remove the low milliamp-hour rated AAA cell and replaced it with a standard 1000ma-hour NiMHAAA cell. 

I then replaced the small 4 cell solar panel with a larger 4 cell unit, which produced 150ma in the sun.  Next, I simply changed the 470uH coil on the circuit board to a 22uH coil.  The lower inductance increased the battery current to 40ma when the LED light was on, which translated to about 13ma LED current.  The light was much brighter.  The 150ma from the solar panel should charge the battery in about 6 hours. 

The larger 1000ma NiMH cell should keep the light going through a long night.  With just a couple simple mods, the light was now much more useful.

More  Solar Cells


List of Dave's Circuits
Dave's Circuits with Descriptions
Dave's Circuits by Category

eMail David A. Johnson, P.E. about this circuit


HOME Schematics Index Hobby Corner Dave's Circuits Electronic Resources Contact Info
Imagineering Ezine    Discover Solar Energy Dave Johnson & Associates Faraday Touch Switches

 About Us   |  Advertise on DiscoverCircuits.com   |   Report Broken Links  |    Link to DiscoverCircuits.com  |    Privacy Policy

Copyright  January, 1998 - December, 2017     David A. Johnson & Associates.  All Rights reserved. 

 Linking is ALLOWED but COPYING any content or graphics to your web site is EXPRESSLY PROHIBITED.