New to Solar Power - Beginner Questions

2 Posts
May 2, 2010 11:59 pm
New to Solar Power - Beginner Questions

My daughter found a small snapping turtle last week. We turned an old tub into his new home. I decided to add a water fall and purchased an 800 gph 12 volt pump. I figured solar would be a cool way to power the pump. I have a 12 volt 12 ah rechargable battery to power the new pump but I am not sure what size solar panel to purchase. I am looking at a 40 watt panel on ebay. It appears I also need a charging controller.

Will the 40 watt panel be enough and what controller do I need to buy?

Thanks in advance,

Shane - Texas
351 Posts
May 3, 2010 02:30 pm
Re: New to Solar Power - Beginner Questions

The big question is, How many hours a day are you expecting to run the pump/waterfall ??  We can’t really give good answers until we know that.

It would help if you would tell us the makes and models of the pump, battery etc.  It lets us tell you whether they are right for the job, and allows us to look up specific info that you may not have provided.

That being said, you have a miss-match between your pump and battery.  Your pump is going to draw about 3 amps. So it will be operating at a C4 discharge rate (would draw the battery flat in 4 hours.)  That is an extreme rate that would result in short life for the battery.  You should be discharging at something near a C20 rate for longer battery life. So that would mean a battery/bank of about 60 AH. (That size is subject to change based upon how many hours you are going to use it.)

I am guessing that your battery is most likely a rechargeable battery that is generally used for standby or electronic use.  If that is true, it is the wrong type to use for daily cycling with a motor load. 
2 Posts
May 4, 2010 12:10 am
Re: New to Solar Power - Beginner Questions

The pump does draw about 3 amps. The battery is a UB12120. I plan on running the pump for about 4 hours each evening and maybe 6 hours on the weekends.
May 4, 2010 06:03 am
Re: New to Solar Power - Beginner Questions

If I could, suggest another alternative?
A linear current booster as opposed to battery/charge controller setup.
Such as, but not limited to -
There may or may not be the need for additional PV. As Mr. Hall pointed out, actual motor load, run time and, if I might add, *insolation are key factors. But experimenting can be fun too. As long as its done safely, (of course.)

* Once you are at this site, try;
1 - average
2 - annual
3 - flat plate tilted south at latitude
4 - then find your location on the map. This will provide, under the very best of circumstances, a general idea of the number of hours that a pump might run during a good sunny day.

Another piece of useful information?
351 Posts
May 5, 2010 02:05 am
Re: New to Solar Power - Beginner Questions

Sounds like the system will work, based on the numbers we have discussed.  A 40watt panel, 60ah battery, and a controller. 

I haven’t used any small controllers for years.  Maybe James or one of the other guys will jump in with a better  recommendation. 

I know Morningstar makes a 4.5 amp controller that ahould work (I’ve never used it),  but it would not leave any room for expansion if you decide to add another panel.  You will have to weigh the decision to go minimal and getting a new controller if expansion becomes necessary versus going with a somewhat larger controller now, that would allow a second panel if it becomes necessary or desirable.

578 Posts
May 5, 2010 10:40 am
Re: New to Solar Power - Beginner Questions

you rang? Smiley

if the system is for fun occasional use and portable as opposed to permanently installed and subject to electric codes(s), then there are many choices.  for beginners, I often suggest something with a display that can let them know basic numbers relating to what is going on with their system.

something like this

if something like that is too expensive, then I would at least suggest something that has a low voltage disconnect (lvd) so that the load will not destroy the battery (at least not right away)


if this is to be permanently installed, then I would suggest listed components, and all the appropriate enclosures and conduits to keep children and their friends (or turtles for that matter) safe. 

hope that helps

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184 Posts
May 11, 2010 07:24 pm
Re: New to Solar Power - Beginner Questions

All things considered, it seems that you will be spending in excess of $500.00 for the system.  Have you considered having an electrician install an underground wire instead?  I suspect that a wire, with ground-fault protection, would be a less expensive solution.  At the same time you might consider including a lamp post as part of the project.

I don't mean to discourage you from solar, but I would respectfully ask you to consider a more practical use for it.  A small PV system with a battery would be a welcome source of electricity when the power fails. As you add to your system you'll cut your electric bill, and become increasingly self-sufficient.  When an ice storm knocked out power at my home for 7 days, my system helped to keep food from spoiling, helped to keep the house warm and well lit, provided the energy to cook food, etc.

On the other hand, what will you do with your PV system when the turtle dies?  Just a thought.


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