Recommended solar panel size for gold sluicing pumps?

Discussion in 'General Electronics Chat' started by goldpanner, Apr 14, 2014.

  1. goldpanner

    Thread Starter New Member

    Apr 14, 2014
    Backpacking gold sluicing equipment prohibits carrying large batteries. So, here is what I have going on right now.

    - One 18 aHr AGM, 12 v. running two water pumps (total 11.5 amp draw).
    - driveway test ran 1 hour 10 minutes before battery dropped to 9.8 v

    Question: What size solar panel should I use with the battery to extend pumping time up to three hours or more? Solar would only be connected while pumping. I use an AGM charger at home. I assume the panel output should be regulated?

    Any advice would be appreciated, as I don't want to damage the battery.

  2. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    Hi and welcome to the forum :)

    And thank you for doing the tests and providing enough information.

    Your two pumps draw a total of 12v * 11.5A = 138 Watts.

    That is quite a bit. You can use two 70W or 80W 12v solar panels in parallel. That will drive the pumps, but only in FULL sunlight. The moment it gets some clouds overhead that will drop to maybe 10% of that power, so your pumps will stop.

    Even then, two 70W panels are huge and heavy and there's no way I would want to backpack them (or that 18Ah SLA battery!).

    My suggestion would be to find some water pumps that use much less current. All pumps are not equal, some will pump quite a bit of water while only using an amp or two. More efficient pumps will mean you only need a smaller solar panel.

    You can google for 12v water pump types, just check the litres per hour (flow spec) and compare to the current consumption spec.

    The most efficient pumps will be small impeller type pumps as often used in pond fountains. These are only capable of a small "head" (vertical distance they can pump) but will move a lot of water.

    Adn keep in mind that the whole thing is only going to work well in FULL, 100% bright sunshine between the 4 hours of about 10AM to 2PM. Maybe 9Am to 3PM in summer.
  3. goldpanner

    Thread Starter New Member

    Apr 14, 2014
    Thanks for the info.

    I am only trying to supplement the battery to extend my pumping time, not substitute for the battery. The pumps are putting out a total of 3,300 gph for a 10 inch sluice box and nothing smaller will do the job. The 18 ahr is only 12 pounds and not too bad in the backpack. It comes down to either carrying two batteries (ugh) or adding a solar panel to supplement the one battery.

    After looking through eBay, I was guessing that a 30 watt panel would possibly let the battery run for another hour?
  4. Bernard

    AAC Fanatic!

    Aug 7, 2008
    Maybe there are some lighter panels, but my 15 W weighs 10 lb & gives 1A; a second battery is looking better.
  5. samuel.whiskers


    Mar 17, 2014
    Backpacking and gold sluicing, gives me a backache thinking about it....
    I would use a 4WD and as many batteries as it would carry.... or a generator....

    RB has given you the numbers....

    Solar panels could never be accused of being compact or light, I'd certainly hate to have to backpack anything over 20-30W for any distance....
  6. alfacliff

    Well-Known Member

    Dec 13, 2013
    there is a formula for horsepower required to pump water, but for any reasonable flow rate and distance lifted, the power is probably too much for a portable solar array, even with a battery. you need a lot of gallons per minuit to sluce gold.
  7. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    Not even close!

    Your battery test shows that it dropped to dangerously low voltage after only 70 minutes of running the pumps, at 11.5 amps.

    The ebay "30 watt" panel will be 30W at peak possible power, about 17v (which makes the spec look good). That is 30/17 = approx 1.76A. And that is when everything is perfect (so the specs look good). I'm assuming 1.5A is more realistic in the field.

    So with that panel the current taken from the battery will go from 11.5A down to 10A.

    New run time will be proportional to that change;
    70 mins *11.5/10 = 80.5 minutes

    I'm wondering about your setup. 3300 GPH is a LOT of water flow, almost a gallon a minute. And you say it is only a 10" sluice box? Are you backpacking the sluice box too?

    In a larger setup you would just use a small generator. Or a small gasoline powered water pump.
  8. poopscoop


    Dec 12, 2012
  9. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    Agreed. And you could probably attach a lightweight 18" bicycle wheel and handles to the little 50 pound generator and push it like a wheelbarrow or a cart. Easier than carrying on your back.