Pond Aeration question

tnndytnndy Registered Users Posts: 3
I want to use a brushless 24v DC pump (that says up to 60v is ok) for pond aeration (small pond, maybe 60' diameter, 8' deep).  I'd like to simply connect a couple of 175w panels (30v) in parallel to the pump leads, and when the sun shines, let it pump.  Anyone done this ?  Question in my mind is would is would it harm the pump if the power output of the panels is near nothing at first and last light of the day ?  I'd prefer to keep it simple, no batteries for buffer, no charge controller/etc....just panels to pump.

Have a SNAP (brand) DC fan in a greenhouse I connected this way....works fine.  Cloud goes over, you can hear the fan RPM drop, or fade away to nothing as evening hits.  Been running for several years now.


  • BB.BB. Super Moderators, Administrators Posts: 30,058 admin
    Should not hurt anything (really depends on the pump motor/electronics designs).

    Linear Current Booster may be interesting (but not cheap):


    Basically, they act like a MPPT solar charge controller. The take the high voltage/low current from the solar array, and turn it into low voltage/higher current for the motor (DC motors need high current for high starting torque--voltage is less of an issue).

    For pumps and compressors that have high starting torque requirements--The "high voltage/low current" from a solar array in the morning may not start a high torque requirement pump until the sun is way up in the sky (and/or you have to add more panels).

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • tnndytnndy Registered Users Posts: 3
    Wheee dang Bill.....that 418 buck price tag is a bit steep for what I'm wanting.   The pump I'm looking at is a Chinese utility pump deal on Amazon for under 50 bucks, so I think I'll just give it a try....wire the panels directly to the pump, and see how it does.  I just want some aeration in the pond for my catfish....gets up mid-summer and we sometimes have a fish kill from lack of oxygen.

    Right now I'm running a little utility pump stuck in the pond using 120vAC with an extension cord.  Got it on a timer so it runs few hours in the morning/evening.  Spits water out a short section of water hose up in the air and back down into the pond.   I have some spare 175w panels I'm not using, and would like to ground rack mount a couple on the edge of the pond, wire to that DC pump and do away with the extension cord/etc.

  • mike95490mike95490 Solar Expert Posts: 8,614 ✭✭✭✭✭
    Brushed DC motors have a flaw, that when running straight off solar, they are "stalled" for hours, running current through a single winding, till there is enough power to start the rotation.   Sun - up and Sun - down are times this can happen, and the winding can overheat and go bad.  Just keep an eye on it.

    Most of the electronic / brushless DC motors will shut down the internal control after the 3rd stall.  Power off reset fixes that.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • tnndytnndy Registered Users Posts: 3
    edited June 2019 #5
    Well, I could put a battery in (got couple spare sitting around), along with a cheapy charge controller, and a DC timer that only let the pump run say 10am to 2-3pm.....and on cloudy/rainy days like today, just wire a switch in to flip it off.....got to pass by the array area anyway on daily chicken feeding.

    Got a little setup like that on an automatic chicken door on one of our coops:

  • TecnodaveTecnodave Registered Users Posts: 418 ✭✭✭✭


    nice coop, yeah do it like your coop, keep it simple and no problems, even with sorta iffy batteries, you are using the sun to power, the battery only stabilizes the system.  I have a few very small solar uses that have only a 12 watt panel, no controller, only a zener diode to prevent overcharging, and a minimum of battery for the task at hand.

    2 Classic 150, 2 Kid, 5 arrays 7.5 kw total  2ea.  2S6P Sharp NE-170/NE-165, 1ea. 12P Sanyo HIT 200,  2ea. 4/6P Sanyo HIT 200, MagnaSine MS4024AE, Exeltech XP-1100,  2 Banks L-16 battery, Rolls-Surette S-530 and Interstate Traction, Shunts with whizbangJr and Bogart Tri-Metric, iCharger i208B  dc-dc buck/boost converter with BMS for small form lithium 8S 16650 or LiFePO4,
  • NANOcontrolNANOcontrol Registered Users Posts: 169 ✭✭✭
    I don't see why linear current boosters are so expensive other than limited production. I modify cheap buck converters so they keep the panels at near power point voltage.  The output becomes a linear current boost and maxes out at the set voltage.  Here is one I use with a 60V array and a cheap $5 charge controller.  The charge controller could be replaced with just a motor.  This $5 buck is good for 12V 5A all day.
  • BB.BB. Super Moderators, Administrators Posts: 30,058 admin

    Do you have a brand/model number and rework instructions that you have used to modify a buck mode switching power supply into a (roughly) constant/minimum input voltage (I think that is what you did)?

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • NANOcontrolNANOcontrol Registered Users Posts: 169 ✭✭✭
    These are sold on ebay as 72V converter 150W 15A.  They are 12V exactly so it will run 12V stuff not charge battery without modification. This particular one sells for $5-6 and can only work around 12V.  The switching chip is uniquely used as a high side driver and will work as low as 30V.  An opto isolator to common sets the voltage with a zener and resistor to the output Break that connection and add some diodes in series to rais it a couple volts.  That module says 20V, left over when I was driving a grid tie inverter.  It is set for 14.5V with that CC.  The following is a generalized schematic that can be used with any buck. Those diodes would tie to the opto LED.  The TL431 can sink down to about 2V and an offset "zener" of a couple volts is needed.  I use a red LED as one of the diodes to indicate when it is inhibiting operation.

    The last picture is the setup to keep my battery charged in winter.  What do I do with the other 500W of panel power? I heat water at power point supplementing my heat pump.

    This is for a 12 panel. the 5.6K resistor is increased for higher voltages.  Voltage on the TL431 never gets above the diode drop.
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