System for Rain Barrel Pump and More

Mar 23, 2014 09:26 pm
System for Rain Barrel Pump and More

I am planning a small (tiny) system to primarily charge and run a small pump to be used to transfer water from my rain barrels to my garden (~50 ft. away).  Since I have access to a 50watt panel (larger than I need), I plan to build the system a little more robust in case I want to charge 2 or 3 larger batteries, to run some equipment in case power goes down (sump pump, beer fridge, etc.).  Does the system I planned make sense or will it work properly:
1) 50 watt marine grade panel, 2) inline fuse, 3) 6A/12V charge controller, 4) 12V, 8Ah(20Hr) Sealed Agm Battery (or Deep Cycle/RV Battery- Group Size 31M, 115AH (20hr)), 5) 200 watt DC/AC converter, 6) outdoor outlet timer, 7) 1/12 HP transfer pump or small bilge pump.
Any comments are greatly appreciate – I realize I’m going a bit cheap here, and that I have no idea what I am doing. Thanks.
10 Posts
Mar 24, 2014 10:05 am
Re: System for Rain Barrel Pump and More

Hi Ken -

I would be glad to weigh in on your project, but before I can, I have a few questions for you. What part of the country (or world) do you live in? Knowing that will make it possible to establish your solar resource and to predict how much energy your system will have to work with. Is this a seasonal project? This also relates to your solar resource in the sense that your solar panel can be smaller in the summer since there is usually more sun. But if you want to operate the system all year around, then there is usually less sun in the winter, which could affect the design. How much water do you want to move per day? Is that amount seasonal? Even a ballpark estimate for this is essential to system design. Is there any vertical lift from where the water is to where it needs to go? If so, how many feet UP from point A to point B (the horizontal distance is less significant)? Do you need any pressure to water your garden - do you plan to use any sort of spray nozzle - or to just let the water flow openly from the pipe?

Please let me know the answers to these questions and I'll get back to you with input for your system design.

Mar 24, 2014 11:12 am
Re: System for Rain Barrel Pump and More

Thanks Bramley - see below for answers in parentheses:  What part of the country (Boston, MA area). Is this a seasonal project (yes, primary use for garden pumping is seasonal, May-September - fyi, I have a 50watt panel already, so I plan to use that.  I would like to have the system available year round for emergencies, but it would get little use beyond the summer).  How much water do you want to move per day (5-15 gallons). Is that amount seasonal (summer only, same amount throughout the season) . Is there any vertical lift from where the water is to where it needs to go (typically 5, but up to 10 ft. lift).  Do you need any pressure to water your garden - do you plan to use any sort of spray nozzle - or to just let the water flow openly from the pipe (minimal pressure, mostly open flow with some drip irrigation incorporated).  (Thanks again)

10 Posts
Mar 24, 2014 05:24 pm
Re: System for Rain Barrel Pump and More

Hi Ken -

From what you say it sounds like the 50 watt panel would be plenty to power the pump. Especially if you have batteries in the system. The load for the pump, 5-15 gpd, with no pressure and 5-10 ft of lift, is minimal. You could even consider running a pump directly off the solar panel and save yourself the expense of batteries and the inverter. A simple 12 VDC pump we carry is a possible match -

By going this route, what we call a DC-direct system, you don't need as much equipment. No batteries, no inverter. If you go this route you can try the pump connected straight to the solar panel and see how it goes. If you aren't getting the performance you desire, you could then consider a pump control box, which would increase the productivity of the pump. And example of a control box it here -

Keep in mind most control boxes are for direct systems only, ie, systems without batteries.

On the other hand, using a timer in a DC-direct system could be a little tricky as they normally require a battery to maintain settings and general functionality. Also, if you want to store some energy for other uses then going DC-direct is not the way to go. But you could still run that pump off a 12VDC battery and also use the same battery to power other 12 V loads. One thing to keep in mind is to have a small breaker box with breakers to protect your circuits.

The parts list you provided looks pretty complete except for all the breakers/fuses you'd need. I saw one fuse on there, but you'd want one for each DC load off the battery bank, including the inverter if you get one. Also one between the charge controller and the battery bank. Another thing you might consider is a surge protection device, which can help to protect your system in the event of a nearby lightning strike. Finally, how do you plan to mount the solar panel? It's important that you find a way to do so such that the tilt angle of the panel and the azimuth angle are optimal for best performance. You can see some of the pole mount brackets we sell here -

You might look at the side of pole mount and top of pole mount brackets we have to offer.

As far as the particulars of the parts you chose, I can't comment too specifically because I don't know the model numbers of what you're talking about. Nor do I know if the battery bank you chose is sufficient given the items you wish to power, without knowing the power draw of each item and the length of time per day you wish to use that item. You can try one battery and see if that meets your needs and size up if necessary. Or you can get more sophisticated and use our load calculator to figure out how much storage you need -

Good luck with your system!


Mar 28, 2014 09:19 am
Re: System for Rain Barrel Pump and More

Thanks for all the help, advice and recommendations Bramley, very much appreciated.  I'll likely steer away form the direct, as I already have some components kicking around (inverter, battery, AC pump) and I want the backup batteries.  I will however purchase the rest of the equipment, and thanks for the fuse advice.  As an aside, I work at a company in Boston who has worked with you guys, and you come highly recommended.  I now see why.
462 Posts
Mar 29, 2014 02:17 pm
Re: System for Rain Barrel Pump and More

just a quick comment on the rain barrel. If you are just using the storage to water a garden 50 feet away at some small elevation, why do you need a pump? Can you raise the rain barrel to a height above the garden and use gravity instead?
Mar 31, 2014 09:31 am
Re: System for Rain Barrel Pump and More

Thanks Tom - simpler is better, right?  But I guess that wouldn't be fun.  I have my barrels (which are actually hard-piped to my sump pump) in an enclosure and integrated some plantings around them so I can't really move them much.  I also want a small system as a back up to my sump pump.  It's a good point, and if I don't get my panel set up I'll look into the gravity feed option instead.  Thanks.

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