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

DiscoverCircuits.com has links to 45,000+ electronic circuits, cross-referenced
into 500+ categories.    We have searched the web to help you find quick design ideas.

HOME Schematics Hobby Corner Dave's Circuits Electronic Resources Contact Info
Imagineering Ezine    Discover Solar Energy Dave Johnson & Associates Faraday Touch Switches
Welcome to DiscoverCircuits.com - online since 2002

See Media Kit for
Advertising Opportunities

Attention Designers:  Please alert us by eMail if we have linked to sites
where your original material has been copied without your permission.
We will change to the LINK to your site.  
Thank you.

 

Circuits designed by David Johnson, P.E.
Last Updated on: Wednesday, October 18, 2017 05:04 AM

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 Circuits

9v Solar Panels Converted to 4.5v Panels - July 26, 2017
designed by David A. Johnson, P.E.

Three 1.2v NiMH cells wired in series are perfect for powering white LEDs.  The 3.6 volts from such a battery bank is a good match for a 3v white LED. Only a single resistor is needed between the battery and the LED to limit the current.  The ideal solar panel voltage when charging three 1.2v NiMH cells, is 4.5v, using 9 solar cells.  A 1N5817 Schottky diode is usually wired between the solar panel and the battery pack, to prevent battery current from leaking back into the panel at night.  A voltage of about 4.08v is needed to charge three NiMH cells in series.  When you add about 0.4v for the voltage drop across the Schottky diode, you get 4.4v.  Thus, a 4.5v solar panel is perfect.

  The solar panel itself limits the battery charging current, based on the panelís maximum current rating.  NiMH cells donít require any fancy charge control circuits.  But, I do suggest keeping the charging current to about C/10, where C is the milliamp-hour rating of the battery.  However, it is difficult to panels with 9 cells.  Most panels from China have 8 or 10 cells. One solution is to purchase an 18 cell 9v solar panel, such as the one shown below, and modify the panel slightly.  As the photo below depicts, most 9v panels are made of two sections of 9 cells each, wired in series.  By cutting the underside copper trace of the panel and soldering two jumper wires, the panel can be converted into two 9 cell sections wired in parallel to form a 4.5v panel, with twice the current as a 9v panel.  The 2 watt panel below can then produce about 450ma at 4.5v.  Larger 4 watt panels are also available and can be modified the same way to generate about 890ma at 4.5v.  I have also seen some 24 cell 12v panels, which could be converted into a 6 volt panel using the same cut and jumper method.

9v Solar Panels 9v Solar Panel
 
  12v 4 Watt Solar Panel
 

More  Solar Cells Circuits

Dave's Circuits


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

 

 


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


Discovercircuits.com endeavors to credit original designers.   Please alert us by eMail so we can
delete links to material that have been copied without your permission
.   Thank you.


© Copyright of all original material on this website is the property
of David A. Johnson, P.E. (Dave Johnson & Associates ) unless otherwise noted.  

Linking is ALLOWED but COPYING any content or graphics to your web site is EXPRESSLY PROHIBITED.
All material is provided "as is" without guarantees or warranty of any kind, either expressed or implied.