Solar powered 12v water pump advise

[Louis Ohland]

I bought a small [11W] solar panel and a 12v water pump a few years
ago for a small fountain. Works fine in full sun, but the panel is
rather adamant on the amount of shade or overcast that it will accept
before it will power the pump.

I would like to get a bigger array and use a battery to store the
extra energy. Common sense is not the overriding concern here. The HF
45W array seems to be quite adequate, but my question concerns the
converter and battery charger [and the type of battery as well!].

Will someone care to guide the solar powered challenged individual
through the process?

 

[SJC]

I bought a small [11W] solar panel and a 12v water pump a few years
ago for a small fountain. Works fine in full sun, but the panel is
rather adamant on the amount of shade or overcast that it will accept
before it will power the pump.

I would like to get a bigger array and use a battery to store the
extra energy. Common sense is not the overriding concern here. The HF
45W array seems to be quite adequate, but my question concerns the
converter and battery charger [and the type of battery as well!].

Will someone care to guide the solar powered challenged individual
through the process?

I would say a battery, charge controller and something to turn the
pump on and off. If you want the pump to come on when there is
enough sun, it would have to be a separate circuit now that you have
a battery. Just a power device that is enabled once the voltage and
current from the charge controller is adequate should do it. Or you
could put it on a timer that takes very little power to run.

 

[Louis Ohland]

Battery type? Lead acid?

 

[SJC]

Battery type? Lead acid?

Depends on what kind of capacity you need, the load and maintanance you
are willing to do. It sounds like the pump takes maybe 6 watts, or so.
Do you want the pump to run even when there is no sun? For how long?
There are a few variables missing.
Lead acid could be the kind you have to add water to or the kind you don't.
I use an AGM sealed deep cycle from Johnson Controls, but most of theirs
are automobile size. If you only need 6 watt hours of storage you could use
NiMH D cells. Those are available at Radio Shack along with the battery holders.
It is up to you.

 

[Louis Ohland]

I'd like constant operation if possible. If not, then shut off on
sundown, my concern is the overheating of the water in a 75 gal stock
tank in direct sun.

 

[SJC]

Sounds like you want to monitor the temperature in the tank and make the
pump operation a function of that. That does not quantify how long you want
the pump to run. So worst case is continuous operation, so you need to find out
how much current the pump takes at 12 volts with what ever head end you have.
24 hours X 6 watts would be 144 watt hours. If your panels can generate 45 watts
(which I doubt) for 4 hours, that would be 180 watt hours. It is those days that you
do not get at least 144 watts hours of solar generation that you are in trouble. So,
maybe you want something that can store 150 watt hours. Johnson Controls makes an
Optima model D51 AGM deep cycle that stores 200 watt hours.

http://www.optimabatteries.com/publish/optima/americas0/en/config/product_info/technology.html

These are available at auto parts stores and the site should be able to tell you where you can buy them.
You also have to look at your charge controller. What hind of battery does it specify. If it does not
meet the specs of the Optima you can not use them or you need a charge controller that meet their
specs.

 

[SJC]

If you are set on purchasing the Harbor Frieght panels, I suggest that you
contact them to see what they recommend. It may just be a regular deep cycle
battery available at auto parts stores.