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Old 04-22-2015, 06:53 PM
jvcstone jvcstone is offline
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Join Date: Jun 2013
Location: North Central Texas
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Default 12v battery/panel combo???

have a 3000 gal above ground water storage--have been using it gravity flow for the garden--which has been a bit of a problem. Mostly, the gravity flow pressure will not push water through soaker hoses very will, and since there is a crown in the garden, the water tends to stay on the side of the crown that the feed line is attached to some perforated 1/2 inch pvc .

Have ordered a small 12v transfer pump that I will put into the system to give me some pressure. Will a battery such as this:
work ok, or would something larger be recommended, and if it will work, what sort of panel do I need to keep up with the pump when it is running, and keep the battery charged, but not over charged when the pump is not running.

This is the pump I've ordered:

thanks in advance

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Old 04-22-2015, 07:18 PM
Lurch Male Lurch is offline
Join Date: Mar 2010
Location: North Idaho
Posts: 233

On my domestic water system I'm using Trojan T-105 deep cycle batteries. The pump is a Shur Flo 4008, 12 volt DC, 3.0 gpm, 55 psi. I have been using this combination successfully for the past 19 years. The batteries seem to last about 10 years- I'm on my second set. I've gotten over 5 years on this Shurflo pump. I always keep a couple of spares on the shelf as well as some pump rebuild kits.
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Old 04-23-2015, 11:46 AM
wywhitewolf Male wywhitewolf is offline
Join Date: Mar 2015
Location: Wyoming
Posts: 69

No that battery is way to small.

The pump is rated at 14 amps. Being that you should never discharge a battery below 50% that means you need at least 28AH of battery for every hour you plan on running it between charges.

Add to that that batteries have a maximum discharge rate that is around C/8 for FLA batteries. 14A*8 = 112AH. AGM batteries are around C/4. 14A * 4 = 56 AH. Those would be your minimum battery sizes provided they are large enough to supply the hours you wish to run the pump. The FLA will supply enough for 4 hours between charges.

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Old 04-23-2015, 11:56 AM
wywhitewolf Male wywhitewolf is offline
Join Date: Mar 2015
Location: Wyoming
Posts: 69

I didn't address the panel size.

To properly charge a battery it needs charged between C/8 and C/12. For the above 112AH battery that would be between 9.3 and 14 amps. So the minimum array should be 167 watts for PWM controller or 140 watts for a n MPPT charge controller.

Either of those should also be large enough for the 4 hours of operation in Texas (3 season). If you wish to run for more than 4 hours per day then you need to add about 50 watts (PWM) or 40Watts (MPPT) to the array along with the 28AH of battery for every additional hour of operation.

Those are the minimum numbers figured at C/12. Increasing the array numbers by up to 25% (to C/8) would not hurt anything.


Last edited by wywhitewolf; 04-23-2015 at 12:07 PM.
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Old 04-24-2015, 08:14 AM
HuntingHawk HuntingHawk is offline
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Join Date: Oct 2011
Location: Florida
Posts: 1,409

I suggest something more like a 29D marine battery ($100) because there could be overcast days there is little charge sent from the solar system to the battery. A pump that draws 14amp & using a 7amp battery doesn't add up.

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Old 04-27-2015, 08:13 AM
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Bearfootfarm Male Bearfootfarm is offline
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Location: Eastern North Carolina
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the water tends to stay on the side of the crown that the feed line is attached to some perforated 1/2 inch pvc .
I'd go "upstream" to the first solid section of pipe before the soaker hose and add a "T", then run a second solid pipe just beyond the crown so the water doesn't have to be forced through the first "leaky" section to reach the second.

It might even be possible to trench across the "crown" to eliminate the rise, depending on it's width

I also agree you need the biggest battery you can get if you have a 14 amp pump and expect to use it for long periods

It's possible though some extra plumbing could do away with a need for the pump at all

You might even be able to establish a siphon to a barrel in the garden to add a little additional pressure to get over the hump
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