Hi brandond,

Check out the internet. Here is a link to solar pumps.

http://store.altenergystore.com/Solar-Water-Pumps/c489/

I have no experience with this type of system. Usually useful for more remote areas that you can't get power to easily ergo more cost. GL Aloha.

I have not seen a 15 amp solar panel at northern tool...you may be referring to a 15 WATT panel (about $150)?? I think that panel would only provide about 0.6 amps.

Im in the process of designing a system that would use a 12-volt demand pump to irrigate my vegetable garden, using a lake behind my house as the water source. I am going to be running some tests this weekend to have the data for final design as I only have estimates for flow data right now. Based on what kind of yield (in gallons per minute) I can pump with the pump I have, I can determine if the pump I have can meet the demand (how much water I need). I plan on hooking the pump up to a 12 volt marine battery and then putting a small battery operated hose timer on the out-flow side of the pump so that the pump will basically operate independently (after I set up the timer) to irrigate the garden (actual time will depend on how much water I determine is needed and how much water I can provide with what I have) - I hope to use a drip emitter system. The timer is just a valve that opens and closes at whatever preset times I choose, and since the demand pump has a pressure cut off, the timer should essentially turn the pump on and off when the timer valve opens and closes.

I got a solar panel and controller to trickle charge the battery...didn't cost me anything since I got it with points I've earned on a rewards credit card. It's an 18 watt panel...but here's the rub:
The charger only supplies about 1.2 amps dc when the sun is normal to the surface of the charger. At any other time, the output will be less (proportional to the cosine of the angle the sun makes with the surface of the charger, to be exact). Unless I have a solar tracker that can change the angle the charger is so that it is always normal to the sun, the output will be less than optimal most of the time. The best I can expect is to place the charger so that it is at an angle equal to my latitude so that I at least get a peak of 1.2 amps when the sun is normal to the surface of the charger. Assuming full sun all day, the average current would be about 0.6*1.2, or about 0.72 amps, and that times a long summer day of say 10 hours, would provide about 7.2 amp-hours. If the pump runs for two hours a day, it will consume approximately 5 amps times 2 hours, or roughly 10 amp-hours. This means the charger will not be able to keep up with the demand if I run the pump for two hours a day, seven days a week (I'm hoping that I won't have to run it that much, though). Also, there is no accounting for cloudy days in those assumptions.

What that all means, is your ability to use the solar charger is limited by it's ability to keep up with the amperage demand on the battery. The solar panel from Northern will give you about 0.6 amps (average) per hour...so you will want to design everything such that the system does not consume more than 6 amps a day (assuming 10 hours of direct sun). You will need to find out what the amperage is on the pump to find out how many hours it can run without exceeding the charging ability of the solar panel.

Sorry for the dissertation...just wanted to get it all in.

Hi Hydro,

Excellent dissertation and very informative to those in more remote regions. Clearly laid out. How much did the panel cost and how long do you expect it to last. I just wonder if it is cheaper to get it hooked up to a regular power source if one is available. Aloha.

The panel I have is a Coleman CL-1200 panel...you can pick one up from Amazon (with free shipping) currently for about $120. The charge controller will run another $30-40. You can get it as a "kit" (panel and controller) at Costco for $140.

I ran some tests on Saturday with a Shur-Flo demand pump. The pump was elevated approximately 6 feet above the water table elevation in the lake, and with 50' of 3/4" garden hose, I was able to get about 2 gallons/minute out of the pump. I used a meter to find the amperage draw, and it was just under 3 amps...which is less than I initially anticipated. I can probably run the pump for an hour a day, seven days a week if needed, but will probably not need to water that much.

Oh, forgot to mention...the panel should last many years as long as nothing falls on it. If you are closer to AC power, it would be cheaper to just use a 115V demand pump.

My garden is located about 200' from my house (therefore 200' from any AC power as well as water from my house). The lake is only 40' from my garden so it's easier and less work to use a 12V battery and pump to irrigate.

HiHydrogeo99,

Sounds like you are on top of it all. Just curious, how much flow do you get out of the pump without the 3/4" hose and what pressure at the pump outlet as well. You might reduce your pressure loss with a larger pipe (1 1/2" pvc) depending on your pressure output at the outlet. But your out put of 120 gallons per days is probably good enough for a garden of 150 plants. Great thread. Thanks. I hope we were of help to the original poster. Aloha