Solar Water Feature Pump Direct to Solar Panel

[colerainescotty]

Hi Guys, I have been having a look for info regarding this but I can't find what I am looking for.

I have bought a 12V DC submersible Water Pump for a water feature that I am wanting to build in my garden in cloudy Northern Ireland. The ebay name of the pump I bought is New 12V DC 1.2A Micro Submersible Motor Water Pump 5M 840L/H 6-15V Hot

So I wanted to do this as simple as possible. I have tried the little solar fountain kit from ebay and they work quite well. I thought I could build something on a bigger scale with better results for our cloudy weather.

The solar panel I purchased for this project is a 10w designed for charging a 12v battery. Just to clarify I do not wish to use a battery if possible in my water feature project.

I have a solar and battery bank setup in my shed for automatic lighting, so I tested the pump using my 12V battery bank from the shed and it is a great little pump. It will be perfect for my water feature if I can get it working. I did try to connect it to my 10W panel and it did not turn at all. It seemed that the panel may be too small for this pump and was not producing enough power even pointed up to the bright sky.

I actually thought that compared to the small water fountain kits that come with the tiny panels and only work in full sun, I was bound to have plenty of juice to run my pump even when cloudy but I think I may have chosen a pump that requires too much amperage (1.2A rated) I believe the 10W panel only outputs around 0.6A peak.

So my couple of questions are:

1) What would you do to achieve my goal of having a directly powered solar water pump for a small water feature but one with an oversized solar panel so that it works even when dull or cloudy?
2) I also thought of downsizing the pump and if I do I may need to limit the amount of current that can get to the pump. The smaller ones used in the kits operate at 6 volts and 120ma which my 10W panel would more than handle. My problem there is that I would probably fry the pump in no time. I have never fully understood why a load can take only what it needs from a battery but with solar people have told me that it can push too much current to the load. Is this true?

If I did downsize the pump for use directly with the 10Watt solar panel, I do have a DC - DC converter that outputs a steady 6 volts to the pump but how can I protect the pump from getting too much current? For example when in full sun the panel can push 600ma or so but the pump only needs 120ma (I think) is there an easy way for me to do this? I am relatively new to electronics but have a keen passion for solar projects.

Thanks for your help in advance and can't wait to hear from you

[colerainescotty]

UPDATE

I tested the setup again in full sun and can confirm the pump worked. So now I am obviously convinced that the panel is inadequate for that pump. So I think what I may need to do is get a pump that requires less current. I only need it for a small water features basically to trickle water down some pebbles. I have been reading other posts about a linear controller. Would this work for this pump at all?

Finally if I do get a pump that runs on much less current do I need to limit the current getting to the pump? I did send away for a DC-DC converter. It converts 12-30V down to 6V and I was thinking of using this on a smaller 6V pump. Any thoughts or info would be great. I do think for my very small application that surly a 10Watt panel can drive something, its just getting the right gear I suppose

Thanks

[Logan005]

You have an 14 watt pump and a 10 watt solar panel.

[Logan005]

you need 3X 10 to 15 watt panels, positioned south east, south and south west with proper inclination. this should be enough to keep your pump running much of the day w/o battery.

[Logan005]

given that a panel produces some power even when not directed to the sun you might get by with a little smaller mid day panel, a voltage regulator would help the pump last longer.

[bcroe]

UPDATE

I tested the setup again in full sun and can confirm the pump worked. So now I am obviously convinced that the panel is inadequate for that pump. So I think what I may need to do is get a pump that requires less current. I only need it for a small water features basically to trickle water down some pebbles. I have been reading other posts about a linear controller. Would this work for this pump at all?

Finally if I do get a pump that runs on much less current do I need to limit the current getting to the pump? I did send away for a DC-DC converter. It converts 12-30V down to 6V and I was thinking of using this on a smaller 6V pump. Any thoughts or info would be great. I do think for my very small application that surly a 10Watt panel can drive something, its just getting the right gear I suppose

You want to chose panels and motors that connect directly, assuming you can tolerate some variation in speed with sun. A converter could
get stuck trying to start the motor as the sun slowly rises, trying to pull starting current directly from the panel instead of multiplying
the current (conversion). A more complex control could get around that.

To get somewhat even power over the day, you might consider some curves like I just did. Note here the highest line is the sum
of east and west facing panels with a properly selected elevation. To make more power/or operate with less sun, just expand the
number of parallel panels to get what you want. See the original discussion on SUN HOURS, 06-19-2016, MODELING BRUCE ROE

[colerainescotty]

Cheers for the reply guys. Interesting things to try. I do have other panels I could use logan005 so will look into this thanks.

Bcroe what complex controls do you speak of? Is it one of those linear controllers? If so do they sell anything on ebay I could use?

[bcroe]

Bcroe what complex controls do you speak of? Is it one of those linear controllers? If so do they sell anything on ebay I could use?

I'll let someone else recommend the correct control; a simple DC to DC converter won't cover all the situations required. Bruce Roe