Need help - powering a submersible pump directly from the charge controller

Berseker

Solar Enthusiast
I am new here, was researching on best way to go about my setup.

I have a 12v 200ah battery, powered by 2 x 250w mono panels in series, hooked up to a 50amps, 12v/24v fangpusun mppt charge controller. all this connected to a 12v 850va inverter. Now i want to add a submersible pump to the mix.

I am considering 2 options
A. buy a 12v 180w pump, and connect it directly to the battery, my major challenge is that its in a remote location, and i would only want the submersible pump to come on only when the sun is bright, so as not to excessively drain the battery. is there an easy way to conviently automate this??

B. buy a 24v submersible pump, and connect it at the pv input terminal of the charge controller, that way.the pump peeds off power from the pv, without drawing power from the battery. i would simply throw in a dc timer switch to enable power to the pump btw 9am and 4pm,

in the 2 options above, i would need to figure out how to wire a float switch to the overhead tank, so as to cut off power to the pump when full
 

Craig

Watts are Watts!
Staff member
Moderator
I posted in other thread but what kind of SCC do you have and what are the panels volts at the SCC
 

Berseker

Solar Enthusiast
I posted in other thread but what kind of SCC do you have and what are the panels volts at the SCC

My SCC is a 12v/24v 50amps fangpusun mppt..
My panels are 24v connected in series, btw 60v n 45v is displayed on the SCC.
I could get a 48v submersible pump as well.
My major concern is if there would be ill effects of tapping pump power supply from the Scc pv input
 

Craig

Watts are Watts!
Staff member
Moderator
I do not see a problem if the pump can handle it. my concern would be making sure you had enough power from the panels to run pump and charge batteries. you could also put a relay that is controlled by the panels if te panels have voltage relay is on no voltage relay is off that would allow you to run pump only when sun is out. you could also tie the relay to battery voltage so it only runs if batteries are above X volts.
 

Berseker

Solar Enthusiast
2 x 250w panels..and the pump is under 250w at 24v/48v, and i have seen harvest in excess of 350w on bright sunny days .

On another forum , some people said its risky connecting the pump to the scc pv input terminal. But failed to explain convincingly what could go wrong.
 

Craig

Watts are Watts!
Staff member
Moderator
Im sure something could go wrong. I would worry that the well pump might try to pull power backwards from the batteries through the SCC the SCC should have reverse current blocking but adding a real load could possibly do something bad.

Personally I do things that you are not supposed to do often knowing that if something goes awry its my fault and oh well lesson learned. But if i do think if you can make sure pump is only on when sun is out that would help.
 

Berseker

Solar Enthusiast
so after much thought, i have decided to make it simple and go for 2 x 300w dedicated panels for just the submersible pump alone...
the pump am considering is 24v/200w or 48v/280w, havent decided on which to go for..
i need help in how to hook up the float switch, to cut off flow when the overhead tank is full. the float switches i saw on aliexpress are AC types, thus not compatible with my proposed application.
 

Craig

Watts are Watts!
Staff member
Moderator
I would put a 24 volt relay on the positive leg from PV. Attach negative line from PV to pump and to negative control of relay. Attach positive leg to relay load and then attach pump to other relay load.

Attach line through AC float switch. One end to relay control and other end to PV above the relay.

This way when Sun comes out if float switch is closed it will pump if switch open no pumping. I think the AC switch will be fine with the very low current draw of the relay control.

I use regular AC switches for my DC lights in my cabin no problem.
 
PV panels heat up solder joints and self destruct. That is but one of many reasons NOT to hook up a pump directly to the PV input. Motors have something called back emf that will try to push hundreds of volts into your panels when the float switch or relay disconnect. The better option would to be connecting to the battery and using a snubber circuit to eliminate the back emf from destroying the scc or pv array. The best option, imo, would be to use an inverter and standard AC pump. Considering the build quality and length of run from the battery to where the pump will be. The AC pumps use much less current and can use much smaller wires on longer runs. They are also much more robust in their construction quality for the same price point. If you inverter has a fit starting the pump, you can use negative coefficient resistors in line with the hot lead to create a soft start circuit. (most name brand inverters have this built in) Hope this helps!
 

Craig

Watts are Watts!
Staff member
Moderator
PV panels heat up solder joints and self destruct. That is but one of many reasons NOT to hook up a pump directly to the PV input. Motors have something called back emf that will try to push hundreds of volts into your panels when the float switch or relay disconnect. The better option would to be connecting to the battery and using a snubber circuit to eliminate the back emf from destroying the scc or pv array. The best option, imo, would be to use an inverter and standard AC pump. Considering the build quality and length of run from the battery to where the pump will be. The AC pumps use much less current and can use much smaller wires on longer runs. They are also much more robust in their construction quality for the same price point. If you inverter has a fit starting the pump, you can use negative coefficient resistors in line with the hot lead to create a soft start circuit. (most name brand inverters have this built in) Hope this helps!
I am not an expert so I can not argue with what you say. But financially wise your proposal probably quadrupled the cost. I also know that at the farm show here in California vendors sell systems that use direct PV input to power pumps. How good it works I do not know.

One thing that would worry me about direct PV connection is what happens if there are not enough amps to run the pump? Will it get hot and burn up.

I would definitely try his proposed system knowing it may or may not work but will not cost anything extra if it does not work.

History is filled with people doing things that they were told can't be done by experts.
 

Berseker

Solar Enthusiast
PV panels heat up solder joints and self destruct. That is but one of many reasons NOT to hook up a pump directly to the PV input. Motors have something called back emf that will try to push hundreds of volts into your panels when the float switch or relay disconnect. The better option would to be connecting to the battery and using a snubber circuit to eliminate the back emf from destroying the scc or pv array. The best option, imo, would be to use an inverter and standard AC pump. Considering the build quality and length of run from the battery to where the pump will be. The AC pumps use much less current and can use much smaller wires on longer runs. They are also much more robust in their construction quality for the same price point. If you inverter has a fit starting the pump, you can use negative coefficient resistors in line with the hot lead to create a soft start circuit. (most name brand inverters have this built in) Hope this helps!

I would also prefer AC pumps, but they are generally power hogs, least i hv seen is 500w, my setup is a basic/budget setup, a single 12v 200ah battery. 500w load on it would kill it. throwing excess panels at it, to meet up with the 500w load, may cause problems for the battery -- over charging, whenever the pump is off.

i understand, most dc pumps that you can hook up directly to solar panels have an inbuilt solar charge controller of some sort.

@BiduleOhm, whats size of diode, do you think would be ok, i must confess, my electrical skills are a lil subpar
 

Berseker

Solar Enthusiast
24v/200w and 48v/280w, these two are top on my list, cos they have higher flow rates. a 3rd option is 12v/180w
 

BiduleOhm

Electronics Sorcerer
Ok, so that's 8.33 A, 5.83 A and 15 A.

So, any one of these will do for the 24 V pump, any one of these for the 48 V pump, and any one of these for the 12 V pump ;)

Alternatively any one of these will be ok for any of those 3 pumps (but that's a bit less cost optimized of course).

I took a margin of at least 100 % so the diode should last far longer than the pump. You don't need a heatsink unless you plan to start and stop the pump 100 times per hour...

NB: you can change the location and currency on the top right.

Edit: you can find the pinout in the datasheet (which you can find under the part reference in the center after you clicked on a component in the list), if you want to make your cabling a bit easier you can chose a 2 pins diodes (a lot of them are 3 pins).
 
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djdubuque

New Member
I just had a system install out in the field and this is what was installed.

Capture3.JPG The red/black is from the panels and the white, black and brown wires go to the pump.


Capture.JPG The unused terminal screws I'm told is for a float switch as I could install a tank if needed.

Still researching what this panel is.
 

Jackofalltrades

New Member
I am new here, was researching on best way to go about my setup.

I have a 12v 200ah battery, powered by 2 x 250w mono panels in series, hooked up to a 50amps, 12v/24v fangpusun mppt charge controller. all this connected to a 12v 850va inverter. Now i want to add a submersible pump to the mix.

I am considering 2 options
A. buy a 12v 180w pump, and connect it directly to the battery, my major challenge is that its in a remote location, and i would only want the submersible pump to come on only when the sun is bright, so as not to excessively drain the battery. is there an easy way to conviently automate this??

B. buy a 24v submersible pump, and connect it at the pv input terminal of the charge controller, that way.the pump peeds off power from the pv, without drawing power from the battery. i would simply throw in a dc timer switch to enable power to the pump btw 9am and 4pm,

in the 2 options above, i would need to figure out how to wire a float switch to the overhead tank, so as to cut off power to the pump when full
I am new here, was researching on best way to go about my setup.

I have a 12v 200ah battery, powered by 2 x 250w mono panels in series, hooked up to a 50amps, 12v/24v fangpusun mppt charge controller. all this connected to a 12v 850va inverter. Now i want to add a submersible pump to the mix.

I am considering 2 options
A. buy a 12v 180w pump, and connect it directly to the battery, my major challenge is that its in a remote location, and i would only want the submersible pump to come on only when the sun is bright, so as not to excessively drain the battery. is there an easy way to conviently automate this??

B. buy a 24v submersible pump, and connect it at the pv input terminal of the charge controller, that way.the pump peeds off power from the pv, without drawing power from the battery. i would simply throw in a dc timer switch to enable power to the pump btw 9am and 4pm,

in the 2 options above, i would need to figure out how to wire a float switch to the overhead tank, so as to cut off power to the pump when full
I bought one of their systems. https://www.rpssolarpumps.com/
 
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