A 15 volt Solar panel powering 12 volt dc bilge pump with no battery. How long will it stay working?

I did a little maker faire project to demonstrate how gravitational vortex power plants work. There was no electrical outlet available so I used a 15 watt solar panel to power a 12 volt 600 gallon per hour bilge pump to keep the demonstration running.  During the maker faire numerous people came between the sun and the panel and the thing stopped and restarted no problem.   I would guess that the bilge pump was running at half strength. (It has a 3 amp fuse so that would mean 36 watts is the max it can do?  An electrical engineer and a computer science student both said that I could probably leave the thing connected day and night and the low evening and morning current would not damage my bilge pump (or the solar panel).  It would just start up whenever the light got bright enough. Would anyone like to confirm that?
Also, is there any arrangement with capacitors so that even the morning or evening sun will turn the thing (even if slowly) or is there a way to shunt that weak power to something useful (Like electrolysis of sea or  salty water to make bleach) and then go back to the bilge pump whenever the sun is powerful enough again?
I would love to know because the project went really well and more could be done with it.

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Qcks2 years ago

Ehh... As far as low current/voltage damaging the pump, it really depends on the control circuitry, if there's any circuitry at all. Electrical motors themselves are pretty robust with regards to tolerating low current/low voltage, but the control circuitry that some types of electrical motors need to run is not.

As far as boosting power to get some amount of work out of the system even in the lowest light type situation, there is sort of a way to do that.
You can use diodes to setup a circuit where you charge capacitors in parallel and then discharge the capacitors in series. This effectively boosts your voltage, but you're still limited by the number of amps that the solar panel can provide at anyone time.
Thinking about it, you might be able to do something with this in reverse as an over voltage protection, where you take a capacitor input and break it up over a diode network to maximize current and limit voltage, but they already have voltage and current regulators that use transistor networks and integrated circuits.
Youtube "Afrotechmod". he has a voltage regulator tutorial that's good.

eenorw2 years ago

I've burned out a couple of "hot water" pumps in my hot tub solar water heater where water is pumped from tub to solar copper water heater box powered with a 15 watt harbor freight panel. Assuming the pumps blew because of voltage drops and/or heat. Used a $18 pump and a $6 pump. Now going to try one that is not submersible but is rated for weak voltage transitional inputs and heat= Topsflo 15PV 12V DC Solar Power Hot Water Circulation Pump.... BTW i also need to add a temp switch because the system works too well, my temps get upwards of 112 F on sunny days. I made a video of my setup, search username Stratoblaster23 on You Tube.

john.o.duke2 years ago

I have gone thru many pumps ''500 gal per hour bilge pump" for a fish pond . The bearing usually give out as gunk gets in the pump and seizes it up (better filtering system), would it be better to use a bigger pump 1500 gal per hour for my

14" x 20 " panel as less strain (amps) on pump ?

gaiatechnician (author)  john.o.duke2 years ago
Hi, John, why not try an air pump instead? Use the airlift process to pump water.   The image below is my tiny airlift pump for watering pallet gardens. You could use the same basic design in your pond with bigger pipes.   If you are only pumping a few ft high,  you can probably  leave out the constriction.     Air pumps for hydroponics are good to pump air 3 or 4 ft deep in water.   And that  air can then pump water up to about 10 ft high without problems.     Depending on how high you are pumping,  you can have a  3/4 inch vertical pipe or up to 1.5 inch vertical pipe.  (for the lower heights)   If you just want to move water in your pond,  then go to kooi vrienden in Belgium.  They bubble  air up large diameter pipes to create currents in the water.  This moves massive amounts of water but  it is not going to work a water feature running into the pond or a fountain.    Hope this helps   Brian
freshpaint gimp tiny airlift.png
inciteman3 years ago

I tried it! Ran a solar panel (80 watt) straight to a submersible bilge pump (1000 GPH, 12V, 5.5Amp Rated), and it ran fine for a few days. But then it STOPPED WORKING or it would stay "stuck" and not start even if in full sunlight. I had to stick my fingers (I know not a bright idea, "but it worked") to start it back up again. I came to conclusion that YES it will get damaged over time due to the low currents in morning/sunset/cloudy times. I'm working on maybe using a circuit with a super capacitor or a constant current circuit, lets see what happens. Did it die? Did you ever find a way to fix it?

gaiatechnician (author)  inciteman3 years ago

I don't know, perhaps it got burnt out at the high end? The solar panels sometimes produce 14 volts instead of 12. So you would have 80 watts into a 70 watt rated pump? Just a thought. Or it might have had some piece of rubbish stuck in it. Don't know. I was told by an electrician, (he paused and thought it through for a few minutes) An American guy who worked on nuclear powered stuff! that it would start up and run fine and then stop fine in low current and that the water was more than enough to cool it at the low end of things. You could have had random bad luck too. I did the walls for a pond last year, and the first $300 dollar pond pump that they installed lasted nearly a day! before it burnt out. The next one is still working. Brian

I doubt the 2 volts over damaged it since normal 12v car/boat batteries are around 13 to 14 volts fully charged. I looked into this further today and it seems the proper way to connect a motor or pump to a solar panel without a battery is using a linear current booster (but their a bit expensive) or using capacitors as a temporary energy source I found a circuit for one called the mini maximizer online and spark fun has something they call an energy harvester. I'm going to try the mini maximizer with a super capacitor.

gaiatechnician (author)  inciteman3 years ago

Sounds like an interesting project. I hope you put it on instructables. What I meant in the last post was that if your pump is 12 volt 5.5 amp, the wattage it is rated for is 66 watts but you are putting 80 watts through it which amounts to overclocking it, and this might have caused your problem, (unless you have a fuse). Perhaps someone else could weight in on this? Brian. Also, the whole brush motor or brushless motor thing could be addressed? I plan to order a tiny airpump shortly, something like 10 watts for all my little (and big) airlift pump experiments. These things used to be non existant (for air pumping) but suddenly there are several options to choose from. I use 1 psi air to pump water. It is distributed on a "pneumatic grid", which means the air pump can be right there with the solar panel. Brian

moffett85 years ago
I would be curious to find out how things go with this. I want to power a dc motor with a small solar panel and am concerned that when the panel doesn't get full sun it could burn out the motor because of repeated low voltage.
gaiatechnician (author)  moffett85 years ago
I am making a pond for my wife (later) and I can tell you then. A bunch of people (including the bilge pump maker) and an electrical engineer that the solar panel and bilge pump will be just fine. Especially because it is "water cooled" it is really safe. I don't know the situation with other motors. sorry. It came as a complete surprise to me that it even worked the thing at all! But to start and stop automatically was better yet. I think that 30 watts of solar panel would be better and closer to its actual rating.
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