Solar Arrays and Subpumps

Was there a battery attached? If not, what sort of voltage regulator did you use? Was the pump run submerged?

Expensive lesson! In fact, they do not behave like a battery. A nominal 12v solar panel could have an open-circuit voltage around 21V. A controller is generally required, whether you have a battery attached or not, to regulate the voltage on the output.

A common model for a solar cell is a diode in parallel with a current source. Put together in a panel, it ends up looking something like this:

I suspect the museum got some freebie subpumps for this effot from a local hardware store. I hope!!

Yes, I suspected that it looks more like a current source than voltage source. The c> >> A museum I help with recently installed a solar array, 3x4'?. They attached

Like hooking up a V-8 to a lawnmower and cranking the throttle wide open then.

You probably need some sort of regulator. Voltage or current.

I think you have your concepts confused, that is voltage and amperage. A device will never "Draw" more amperage than it needs, but if you supply too much voltage it will destroy the device. The likely problem is that your solar panel is supplying too much voltage for your pump and is burning it out. The solution is to get a voltage regulator of the same voltage that the pump is rated for.

- Mike

You're probably right about the voltage, but I believe another poster said it (array) was a current source. Doesn't a current source "draws" voltage in the same manner that a voltage source "draws" current?

If I have a wall wart that is rated at 12v dc and 1 amp, and I attach a device requiring 12v and 0.5 amps, then it will work fine. If the device instead requires 2 amps, it isn't going to work at all. It can't draw 2 amps (perhaps it has a current regulator?).

If instead, I have a device that's a current source, it will try to "draw" the needed voltage. Applying this to the array, then it will try to draw more voltage than allowable if there is no regulator to constrain it. Maybe this has nothing to do with "drawing".

Voltage/current regulator? Is there such a th>> I suspect the museum got some freebie subpumps for this effot from a local

Think of the solar array as a 20 volt battery, until loaded to its maximum current rating.

There are both voltage and current regulators. You probably need the standard shunt regulator that will load the solar panel as needed to keep the voltage within acceptable limits.

What are the maximum voltage and current ratings of the solar panel? You will need this information to get the correct regulator.

Prices start about $30 for the smaller 12 volt units:

John