Controller/Current Boosters vs Voltage Regulator for Dankoff Slowpumps

Graham ParkinsonGraham Parkinson Registered Users Posts: 73 ✭✭
With Dankoff no longer being supplied linear current boosters can anyone recommend a simple controller/current booster for Slowpumps, or offer any experience with going PV direct without a controller? 

We have had a PV direct pump running on two dinky 50W panels and a simple little Dankoff current booster for over 20 years and it works a treat.  We now need another setup and it's going to cost a lot more, although the pumps haven't really gotten much more expensive.

Sunpumps makes some very nice pump controllers but at ~$600 they are expensive overkill that costs more than the Slowpumps (MPPT, current boost, lots of controls on max I and V,  LCD readout, float switch inputs etc.).  Worst, they are designed for high voltage pumps (up to 195 Volts DC) and the manufacturer doesn't recommend using them for pumps with voltage lower than 48 VDC.  The problem is that given the headroom required for MPPT this means enough panels in series to create a Vmp in to the controller of 60 VDC to 72VDC which means at least two big panels with Vmp 33V each (so about 640 Watts of PV to drive an application that only requires 150W). 

Now that panels are cheaper than current boosters, has anyone just overpanelled these pumps to get enough starting current instead of using the current boost from a controller? This would require protecting the pump from overvoltage with a simple voltage regulator circuit and using relays for float switch control.

Offgrid in cloudy PNW

MacGyver'ed museum collection of panels, castoff batteries and generators - ready for state of art system install ....


  • BB.BB. Super Moderators, Administrators Posts: 32,008 admin
    Our host has one ($200):

    Amazon has a couple:

    I don't know anything about them and if they will meet your needs or not.

    There was a company that made little "weird" but nice DC to DC converters for various uses that NAWS used to sell few years ago--Then one day they went to order more--And the company had shuttered its doors (no notification).
    It is difficult to compete with Big Asia electronic do-dads.

    There are a ton of DC to DC buck down converters on Amazon (and EBay)... You have to read through the specifications to see if the input/output/current meets your needs... And you may have to guess and buy a couple different ones to see if they "cleanly" boot from AM sun and Cloudy weather (they may "lock up" if loss of input power, or the pump may stall and prevent the converter from restarting its input):

    There are a few MPPT capable DC to DC buck converters (for charging batteries?) that may work for small pumping system:

    I am sure there are others out there--Just not easy to find.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Graham ParkinsonGraham Parkinson Registered Users Posts: 73 ✭✭
    Thanks BB

    Appreciate the links

    Running the Shurflo 9300 at it's full capacity of 150 W (which is what we need) might be a bit much - Maybe adding a heatsink plate to mount it on.

    The UPNE Tech specs on Amazon look great but the only review said it stopped working in days .....

    On to research buck-boost converters!

    - Graham

    Offgrid in cloudy PNW

    MacGyver'ed museum collection of panels, castoff batteries and generators - ready for state of art system install ....

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