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Trying to set up a solar charged, battery operated pump
Cliffh:
I've got a small (<1/4 acre) pond on the property. To aerate and keep a little water movement I've been running an extension cord from the shop to the pond to run a 1/2hp sump pump. I'd set the pump in a container, with a timer to run it a couple times per day for 15min or so. Off the pump is a vertical 1 1/2" pipe with a 45* elbow at the top. This has worked OK, with a few exceptions:
I have to dig back into the bank, by hand.
It's cost me more than one good extension cord.
An extension cord is not a good solution for the power supply.
This year, I'd like to try something different. I'd like to setup a 12v battery with a solar charger and attach a self-priming 12v pump to the battery. The pump I'm currently looking at has 3/4" garden hose fittings for the inlet & outlet. Pushing the water through a garden hose instead of a 1 1/2" pipe will require running it for more than 15 minutes at a time, or more times per day. That'll depend on how the water's looking after a few days. The mount for the outlet will be easier to rig, and there is a good variety of nozzles to get an acceptable spray pattern.
Looking at HF, I've come up with these items:
https://www.harborfreight.com/25-watt-solar-panel-63940.html
https://www.harborfreight.com/12v-35-ah-sealed-lead-acid-battery-56770.html
https://www.harborfreight.com/7-amp-solar-charge-regulator-96728.html
https://www.harborfreight.com/12v-dc-transfer-pump-290-gph-63324.html
Still have to source a 12v timer.
I've got a few questions, and probably more that I don't know to ask:
How do I compute the run time for the pump without draining the battery too far? Down to a point where the solar panel can't get it back up to full charge before the pump comes on again. How long will it take the solar panel to charge the battery? Is that enough battery? Would a deep cycle battery be necessary?
I could use a convertor and run a 120v pump.
The pump description says it's self-priming, but I think I'll be putting a check valve inline.
Brad Johnson:
First thing that stands out is pump drawing 50 watts but solar panel is 25w max. Unless you're commited to less than an hour or two of total run time per day, you'll never be able to keep the battery charged.
For a 50w load plus efficiency, transmission, and controller losses you're gonna want a 100w panel, minimum. 200w is preferred unless you plan on having some type of motorized tracker to optimize panel exposure.
For what you'll have in panel, pump, and controller, you could run DB cable and mount a weather-rated box on a post or pole right at point of use.
Brad
Kingcreek:
Are you committed to solar electric?
My neighbor aerates his pond with a windmill pump. Seems to work very well.
AZRedhawk44:
First thing I note is that you were previously running a 1/2 hp pump. One horsepower is equivalent to approximately 700 or 750 watts. The old pump is about 350ish watts. Your replacement pump is only 50 watts. It's going to need to run a lot longer in order to cycle as much water. This also corresponds with your pipe/hose diameter where 1.5" will move considerably more water than 0.75" pipe. 0.75" has a surface area of 1.77" while 1.5" has a surface area of 7.06". It's about 4x the capacity (go figure... double the radius and you get 4x the capacity).
You need to run this pump 6-8x as much to effect the same water movement.
The battery you linked claims to have 35Ah of usable power. 12v @ 35Ah yields about 420 watts usable storage, but I'm skeptical you will get a full 35Ah out of it and have the battery remain usable for long. Your pump sucks 50 watts so in theory this battery could run it for 8 hours, but that would be abusive to the battery.
I'd suggest a 25-50% duty cycle through the day as long as you have sunlight, and to get a 100 watt panel since it will only get 100 watts at peak sun position, and you'll probably only get 10-20 watts charge rate for the hours nearest sunrise and sunset. Overcast conditions will weaken the charge rate further.
Cliffh:
The system doesn't have to be solar powered. I am trying to avoid digging a 60ish foot ditch, but looking around at solar options I'm not coming up with anything practical. If I do break down & rent a ditch witch my options open up dramatically with 120v stuff.
And the 120v options seem to be much less expensive than the wind powered options a quick search found. They seem to be starting around the $800 mark. A 100' roll of 10/2 is a lot cheaper, and would put power out there that DW has been asking for.
Now to work in the time around "The List" and doctor appointments....
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