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I have a solar panel:

  • Output power 10 watts
  • Operating voltage 12 volt

I want to run a small water pump maybe 3W small submersible pump.

How can I connect the pump with the solar panel? Someone said I need to use something to control power output from the solar panel.

Solar panel

Water pump

Alternative water pump

Do I need DC DC converter?

I am trying to build a small water fountain for birds due to high heat in summer.

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  • \$\begingroup\$ Do you have some kind of link to the datasheet or product page for the solar panel and pump? It would be helpful if you could edit the original question to include that information. \$\endgroup\$
    – mkeith
    Jun 8 at 7:51
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    \$\begingroup\$ Buy a small, low power 12V pump. Connect it straight to the panel. It'll run most of the time when the sun is shining. \$\endgroup\$
    – JRE
    Jun 8 at 7:59
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    \$\begingroup\$ It probably will work just fine like JRE says. But there could be a slight chance that the panel will over-volt the motor if the motor does not need the whole 10 Watts. \$\endgroup\$
    – mkeith
    Jun 8 at 8:09
  • \$\begingroup\$ I added the Links \$\endgroup\$ Jun 8 at 8:14
  • \$\begingroup\$ @jigneshsorathiya that one won't work, it's for AC power. You'll need a 12V DC pump. \$\endgroup\$
    – DamienD
    Jun 8 at 8:30

1 Answer 1

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Solar panels have a non-linear voltage/current curve. The actual voltage and current depends on the load. This graph is from a different solar panel (from this answer) with more current - same voltage though:

I/V curve for a different solar panel

The specifications for your solar panel:

Wattage (Wp): 10
Voltage at Max Power, Vmp (V): 16.85
Current at Max Power, Imp (A): 0.59
Open Circuit Voltage, Voc (V): 20.9
Short Circuit Current, Isc (A): 0.65
number of cells: 36

You show two motors. The first one absolutely won't work because it's designed for 220V AC. The second one is designed for 9V and 0.22A. If you connected it to this panel it would probably get something like 18V and 0.44A, and burn out.

You have a few options:

  • Get a pump that's a good match for the panel, then connect it directly. If you find a 3W pump designed for maybe 17-18V then it will probably work (I won't guarantee it). The current will be lower than Imp, so the voltage will be higher than Vmp, so you can get a pump designed for whatever voltage the panel actually puts out.
    The voltage should be an approximate match. The current doesn't need to match. But the voltage should approximately match what the solar panel voltage will be at that current, which you'd have to guesstimate. It doesn't have to be an exact match - only approximate. The pump will be okay with a bit too much power or a bit too little power, just not way too much or way too little.
  • Use a DC/DC converter to convert the solar panel output to a stable voltage (whatever voltage you need for the pump). This is the best option. The converter will even try to keep the voltage steady when the sun goes behind a cloud.
    Note: If the solar panel can't put out enough power (e.g. at night), there is a chance the converter will get stuck drawing the short circuit current and you'd have to unplug it and plug it back in to make it work normally. I'm not sure this can be calculated without knowing all the technical details of the converter design. Since other people are using them, I guess this problem doesn't happen.
  • Add a big resistor to waste current and force the solar panel voltage down to the voltage the pump needs. It's not as good as a DC/DC converter, but it could be cheaper if money is a problem.
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  • \$\begingroup\$ can you share any dc to dc convert that can support this panel and i can run any pump? \$\endgroup\$ Jun 8 at 11:37
  • \$\begingroup\$ @jigneshsorathiya they are common - just check the input and output voltage and current. For a DC-to-DC converter, the output voltage might be adjustable (with a screwdriver) or it can be the right voltage, the input voltage is probably a range like 6-30 volts, and the output current should be high enough for the pump \$\endgroup\$
    – user253751
    Jun 8 at 11:38

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