Hi, i've been trying to find a simple 12v stabilizer for a 120watt panel. I have a PWM but it will not power the load without a battery. Google searches pull up car battery voltage stabilizers but i'm not sure if it will handle a voltage flux of the panel. any suggestions?

 

I assume when you say voltage stabilizer, you mean a stable 12 V output, regardless of the input voltage. Automatic stabilizers are of two general types (there may be more), you will have to carefully read the technical data to distinguish them. 1) is a simple buck converter which cannot produce a voltage higher than the input. In fact, if the source is exactly 12 Volts, the buck output will have to drop this slightly below. 2) A more sophisticated DC/DC converter will buck or boost the voltage as needed to achieve the voltage you need. Some will also provide galvanic isolation.

All that being said, solar panels do not behave like batteries. Batteries are voltage sources and photovoltaic are current sources. Depending on the irradiation level and loading you will see a widely varying current and voltage characteristic. In fact, some people talk about controlling the panel to a maximum power point and tracking on that point (MPPT). Check out the resources here:
http://en.wikipedia.org/wiki/Theory_of_solar_cell
http://en.wikipedia.org/wiki/Maximum_power_point_tracking


-doug

 

I've built and used a couple of these with success. But as already said we need more details about your equipment and needs. Too general so far.
http://www.cirkits.com/spc3/

 

I'm dealing with a similar type of situation regarding an uncommon use of solar cells, in my case I'm charging ~50V of lithium cells from a "12V" 100W panel (actually about 17V in operation) and I used a module that's basically the opposite of this unit.

http://www.amazon.com/DROK-4-5-30V-...2241973&sr=1-3&keywords=buck+dc+converter+12a

The unit I linked to will take in the higher voltage of the panel and put out 12V (or whatever voltage you set with the adjusting screw) within the limits of the panel. You won't be able to draw more watts from the module than the panel will supply at any given moment though.

What I find with my setup is that if you load the module too much for the panel the output current and voltage start oscillating, first low and then high, the module isn't really designed to do what I'm doing with it but stay within its limits and it does a surprisingly good job.

 

a lot of the commercial charge controllers for solar are shunt regulators, designed to keep the voltage from exceding the charge voltage of batteries. running a motor directly off solar is dificult because of the starting surge rquired by motors makes the solar panel really large. the battery system supplies the startup surge needed by the motor.,

 

Re Post #5, for motor starting from a solar panel, if motor is manually switched on, adding a large capacitor in parallel with panelwill usually work. The C is big enough if charged to OC V, will run motor for a few revolutions. For automatic start something like a " Mini-Maximiser" or Solar Gleaner might work.