simple solar panel project

Thread Starter


Joined Jul 30, 2014
I have 2 fans and a solar panel from harbor freight. I want to add these fans on my small green house for circulation. The first fan is a dc 12v .14a and the 2nd is 12v 24a. The solar panel is 12/24v 1.5w. What volt battery would I need and what circuit would be best to use. I like to build things. Any advice would help


Joined Feb 19, 2010
24 amperes is a LOT of current.

If I am reading the solar panel info right, at 12 volts you will have 125 mA of current, at 24 volts you will have 62.5 mA of current.

The other thing is that to charge a 12 volt car battery (lead acid tech) you need to apply about 14-15 volts to the battery.

Have you considered using a single fan and try "pull though" setup. In this case you have an enclosed space with two holes. You put the fan in one hole and let it blow air out of the enclosed space. This air moving out will in turn pull air from outside through the second hole into the enclosed space. For this the 12 volt 140 mA fan would work just fine, you could use just one 12 volt car battery. Now just figure out the charger circuit that goes between the solar panel and the battery.


Joined Nov 27, 2006
You may be able to run 12v x 140mA fan from this panel on a bright sunny day by connecting it directly to the panel.
Yes, and because the solar panel is only 1,5W, just shunt the output with a 5W zener diode of around 12V. Connect your fans and they run as long as it is daylight.