I needed a KISS DIY Solar Panel Charge Controller a few years ago to charge a 6 V solar flash light when camping or for QRP work when I am outdoors. Yes there are many such projects on the Internet. I decided to build the controller described by Rick KC8AON available HERE. It is very simple to build there a KISS project and it works as prescribed.
The circuit is nothing more than a standard LM317 3 terminal adjustable voltage regulator mounted on a scrap piece of copper clad board that I cut traces on with a Carpet knife, and a couple of resistors and capacitors. it has one variable resistor to set the output voltage with, and you can set this to 13.5 volts for a float charge, or around 14.4 volts for a quicker charge.
KC8AON's article explain in detail how to construct this controller and therefor I will not go in to detail except to draw your attention to the following:
- I have added two diodes to the output and input for protection
- WARNING: This charger has no automated cut-off when the battery is full. It will keep on charging. So it needs to be under full time observation when charging a battery.
- Float Charge = 13.5 V and 14.4V for charge. Set by 5K preset.
- To charge a 6 V battery use a fixed 220 Ohm Resistor.
- To charge a 12 V battery us a fixed 150 Ohm Resistor.
- I use a 3 W Polycrystalline Silicon Solar Panel with a Vmp of 10 V (Note: If you want to charge a 12 V battery then you need a solar panel of at least 17. 5 V Vmp.)
Finally: This little charge controller served me well and is still in operation today.
Images: (Click on images for larger view.)
