Solar powered, 12v water pump for small pool

[ohland]

Summer's slowly returning, and I need to replace a small solar powered pump (finally died) that circulates the water in a small pool (pool from Menards). Without circulation, the water gets a little scummy...

I have a 12v low maintenance auto battery. A decent south facing position. Time.

What I'd like to come up with is a self-charging system that can run and charge a small pump, no fountain. Small head, maybe 2ft max. The pool is a bit cramped for my Brittany Spaniel, so no in-pool stuff. I can always sink a hole for the pump next to the pool so once it is primed, it will maintain suction.

This is the huge lake were discussing, kidney shaped, about 18" deep (2/3rds) to @8" deep (1/3rd)

Attachment 137413

[enfield]

That sounds like a good idea, maybe if it was on a timer so it would only run for an hour and charge for 2 or something it would stay ahead of the discharge ?

[DCM]

The timer is an Excellent idea.
Another thought and question what is the wind like in your neck of the cheddar?
Would it be possible to use wind instead?

[ohland]

The timer is an Excellent idea.
Another thought and question what is the wind like in your neck of the cheddar?
Would it be possible to use wind instead?

Though I do have good sun from @0700-1300, the trees are to the N, NE and S. Not an open prarie by any means. Though for the past few weeks we have got 10-20 MPH during the day. Right now it's 14mph or so.

Timer? The solar panel will be set up facing due south, adjusted by hand for solar angle if needed.

The old setup used a 6v DC pump, directly connected to a 6x9 (roughly) solar panel, low flow (enough for a small fountain). Not seen too many 6v pumps listed. Not looking to drive a fountain, just recirculate water to perhaps 1' height above the pool.

Calculating the solar panel output (volts and amps under load), controller power use, volt and amps needed to charge the battery, v/a to run pump. This may turn out to show a need for more panel than I'd like to buy, or ditto for a pump, or ditto for a controller.

I suppose the best way to put it is "It depends"

[MaryB]

http://www.amazon.com/DC12V-Submersi...+fountain+pump maybe... don't know how many GPH you need...

Run direct off the solar panel during the day and let it shut down at night. Solar panel https://www.solarblvd.com/product_in...oducts_id=2658

Charge controller if you want to use a battery setup https://www.solarblvd.com/product_in...oducts_id=2911

Would need some form of low volt disconnect though to keep from killing the battery over night.

[ohland]

http://www.amazon.com/DC12V-Submersi...+fountain+pump maybe... don't know how many GPH you need...

Run direct off the solar panel during the day and let it shut down at night. Solar panel https://www.solarblvd.com/product_in...oducts_id=2658

Charge controller if you want to use a battery setup https://www.solarblvd.com/product_in...oducts_id=2911

Would need some form of low volt disconnect though to keep from killing the battery over night.

Did a little surfing last night, looks like the low-maintenance battery is not suitable, should be a deep-cycle battery.

[ohland]

http://www.amazon.com/DC12V-Submersi...+fountain+pump maybe... don't know how many GPH you need...

Hmm, 300mA, 200L/H (44GPH). I have a 185gph that I use next to the house and it is too much for the 50 gallon stock tank, makes the fish swim all the time. OK, 300mA, now to look at panels...

[ohland]

Run direct off the solar panel during the day and let it shut down at night. Solar panel https://www.solarblvd.com/product_in...oducts_id=2658 Charge controller if you want to use a battery setup https://www.solarblvd.com/product_in...oducts_id=2911

Where is a site that covers hooking up a charge controller, pump, and battery? The Solarblvd unit shows connections for the + - Solar panel leads and + - to the battery. I used to have a number of sites bookmarked, but that Vaio is long gone.

[ohland]

http://www.solar-electric.com/deep-c...tery-faq.html/

[RogerDat]

You need to start with how many amps the pump draws.

amps the pump draws x hours of operation = amp hours of charge you need to collect.
battery should not be drawn down below 50% and deep cycle will have amp hours it stores. Going to use 100 amp hour capacity for an example.
while solar panels are typically listed by Watts as in 50 watt panel what you really care about is the amps.
Amazon has a large selection of solar panels and charge controllers (which act like a voltage regulator so you don't cook your battery)

You can generally figure on 4 hours at 50% of solar panel output and 4 hours at 100% output. Daylight hours may be more than 8 hrs. but some of that is not at optimal angle etc. So the 4 & 4 is a good rule of thumb.

So if a 100 watt panel produces 4 amps that means you can put 4 hrs x (.5 x 4 amp) = 8 amp hours plus the full output as 4 hrs x 4 amps = 16 amp hrs. for a total of 24 amp hours per day of sunlight.

You could run something that draws 1 amp for 24 hours, but something that draws 2 amps for only 12 hours. If you pump draws 4 amps it could run for 4 hrs. off of the charge your solar panel puts back into the batter.

If your battery stores 100 amp hours you can draw down 50 amp hours before pulling it below 50% charge (batteries deteriorate rapidly from going below 50%) So once you know how much your pump draws you will also know how many hours the pump can run off the battery if there is no sun.

All works out to a balancing act. You need to take less from the battery than 50% of the amp hours the battery stores and have a panel that using the 4 & 4 rule puts back in more amp hours than the pump uses so that the battery gets fully charged on a sunny day. Even if battery is starting the day at 50% charge. The suggestion to use a low battery shut off and a timer I think is a good one. The thing I think you will have to protect against is never being able to fully charge the battery which will tend to cause it to deteriorate much faster. Your shut off will have to remain off until battery is fully charged.

As with most of these solar type applications getting the demand side lower makes it a lot easier to make the producing side work. One thing you might add is a small LED light. Provides a little ambiance and lets you know the battery has power. These LED lights draw milli or millionths of an amp so not going to run down the battery much faster especially compared to a pump.

Huge advantage to purchase of true deep cycle rather than deep cycle / starting often sold in big box stores. Bit pricey but check out Interstate Batteries to get some ideas. Might call and ask if they have any "blems" at a discount. Costco has pretty decent prices and reported reliability for the combined deep cycle / starting type. Which are the type more commonly used in boats and RV's.

[enfield]

Water wheel, windmill, solar powered with a hamster spinning a generator for back up should be all you need.

[Petrol & Powder]

I think the OP has a sound idea. If a battery is used in conjunction with a solar panel then some type of timer will be needed to limit the number of hours that there is a draw on the battery. I agree with RogerDat in that the cycle time should be kept below 50% so that the charge controller becomes the secondary control to the timer. In simpler terms, the timer becomes the absolute limit on run time and the low voltage shut-off becomes less relevant assuming you don't have several days of little sunlight, in which case the low voltage shut-off will trump the timer.

Now, if you eliminate the battery you can make the system simpler but the pump will run for longer periods of time and it must also be capable of low voltage conditions of partial sunlight.

Of those two options the battery/timer/charge controller is more complicated but will probably result in longer pump life due to lower overall cycle times.

[MaryB]

They make low voltage disconnects for solar stuff, but usually high amperage designs, thi sis about as low as I can find without going to an electronic kit of some sort http://www.newark.com/alfatronix/pt1...9588875|plid||[keyword_text]|match|b&CMP=KNC-GUSA-GEN-SKU-MDC-ALFATRONIX?gross_price= has an advantage of being a simple inline design between the battery and the pump.

For wiring the solar panel goes to the charge controller, charge controller output goes to the battery. Low voltage disconnect would also be connected direct to the battery with the pump connected to the low voltage disconnect.

Fairly simple system I could wire in my sleep... this is my solar control panel



Battery bank

[Petrol & Powder]

You can get a small controller with a lvd

[RogerDat]

This is a highly rated controller with low voltage disconnect, not the cheapest but it is set in epoxy and sealed making it better for outdoor applications. http://www.amazon.com/Morningstar-SS.../dp/B007NNF66K

One the least expensive side you can get a sunforce 7 amp for $22 but I'm pretty sure that won't have the LVD.

[ohland]

Fairly simple system I could wire in my sleep...

Your dreams would terrify me.

[MaryB]

lol I did this for a living, 27 years repairing electronics(consumer to industrial)... yes some of the higher priced controllers have the LVD built in, it is all a toss up as to budget... once you settle on components I could draw a wiring diagram for you.

[ohland]

once you settle on components

I survived cleaning up one pile of raspberry vines... ow, ow, ow, but it feels so good when I quit... Now they are a wisp of smoke and a small pile of ash. Trying to git r done before open burning ends with the start of May. Wind was under 10mph, almost calm, as it were....

Looks like the pump will be 12v, 500mA or less (I've seen 350-400mA), planning factor of 6watt/hour. I know for those off the grid, that isn't even enough to turn on their lights... If things are reasonable, I'd like to have a few gold mollies in the pool to give Belle something to chase.... Direct sun from 0600-1400 daily.

Maximum run time will be 12 hours a day, or 72 watt/hours...

That leaves how much panel is needed to drive the pump, plus enough to charge the battery to make it all night.

Or maybe the important thing is to run the pump for a few hours after sunset to keep the oxygen levels up. After say 10PM, the pump shuts down until @0700 the next morning.

Battery type, deep cycle, 105Ah, something normally stocked... Battery will be in a battery box with terminals, akin to fishing boat ones. Either sitting on the ground, or dug in (gets a bit hot in late July/early August).

Looked at that solar charger, much more ampacity than I need (so it appears).

PS. If the wind was constantly like it has been the past month, I'd do wind. But a lot of time in the worst heat, there ain't much wind...

[MaryB]

You will need 10 amps of charge off the panel(or close), typical is C/10 where C is battery capacity in amp hours. Something like this for the solar panel paired with a 15 amp charge controller(you don't want to be running on the ragged edge of maximum current and create excess heat) https://www.solarblvd.com/product_in...oducts_id=2868

[ohland]

As always, I start unencumbered by reality, and when the little things like cost impinge, I rethink things...

Thanks, Mary, for sifting through the incoherent ravings... I have no doubt the 150W panel with solar controller, plus battery...

About the first week of May, I'm checking in with Ed Kirkpatrick to see if my MGM barrel is in. About then is when Starline MIGHT have done a run of 414 SuperMag brass. The panel is a bit more than the cost for a brand new 414 SM chamber reamer.

Time to dig up the old panel, test the voltage out, and grab a small pump for it. Not perfect, but it will work.