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Any thoughts on how to convert this pump (http://www.harborfreight.com/500-gph-bilge-pump-66094.html) to solar? Answered


Yes, as Jim says, and an undervoltage lockout, because this kind of thing is cooled by the water pumped through it.

Dang, the spec for the current was pretty well hidden.  I think all they give us is this quote from the manual:
(here: http://manuals.harborfreight.com/manuals/66000-66999/66094.pdf )
Note: 5 AMP fuse is required for installation of SKU 66094 Pump.  15 AMP fuse is required for SKU 66095 Pump.

Anyway, knowing how much power you need, or energy per unit time, is important.

Assuming that you just want this pump to run only when the sun shines, and you want a photovoltaic module (a.k.a. solar panel) which drives only this pump, then the problem is picking out an appropriate sized module, one which is "matched" to the power requirements of the pump.

The first step is easy. You want a module that produces approximately the same voltage as that required by the pump. The answer for this is 12V DC. Fortunately, this number, 12 V, is sort of a "standard", and a popular one. So the first step is to make sure the PV module is a 12V one, nominally.

The second step is to figure out how much current, or power, you're going to need, and that's why I was searching through the pump's manual for an answer to this question.  Again, assume the pump really does have a voltage of 12V across it.  The power it consumes is P=I*V, so if it's drawing 4 amps, then the power it's consuming is 4*12 = 48 watts.

Then you find a 12V PV module, rated for approximately this much power. For example, this page:
lists 12V solar modules, with rated power from 1 to 100 watts.

PV is kind of expensive. About the best deal you can find on this page is around 5USD/watt, or circa 250USD for a 50 watt module.

But don't run out and buy a 50 or 60 watt module just yet.

(you know, actually pumping water) with an ammeter, to see what the power requirements really are, rather that just sort of guessing based on what size fuse it has.If you actually have the pump, it would be worthwhile to test it, under load  This step would be worthwhile, if it turns out the running pump only uses half as much power (e.g. 2 amps) as you thought it did, because then you'd only need half as much solar panel. 

Also note that the assumption that the voltage across the module, or across the pump, is exactly 12 volts, this is not really true, but only approximate, the exact voltage there depends on both the I-V characteristic of the module and the I-V characteristic of the pump.

 A BP 75watt solar panel should provide about 6.5 amps in full sun. This would be enough to power the motor. Not sure what your application is for this, but the pump will not run at night, and will run slower or even stop depending on clouds. You may need to include a controller of some sort to prevent from damaging the solar panels as motors tend to draw a lot of current when they are starting.

If you want to include batteries to run this at night you'll now talking about a Charging Controller, so you don't overcharge the batteries. You're going to have to do some math to calculate recharge rate for the battery (or batteries). I would guess if you had two batteries (automobile type), and two solar panels, you should be able to keep the pump running, but then cloud cover over several day could deplete the batteries.

You don't "convert" it to solar, you just provide enough energy to it from a solar panel to run.

It needs around 4Amps to run, so either you need a panel that can supply 4 A at 12V or you have to charge a battery/



8 years ago

i dont know much about solar power but you would need a solar panel a battery like a car battery or boat battery. also you would need a capacitor to bring up the voltage from the panel which would charge the battery.  then you would run the pump off the battery. 

i am not sure of all this info so dont rely on me.  this is just a guess.