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Small Cabin Forum / Off-Grid Living / battery power for water pump. Question
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Ontario lakeside
Member
# Posted: 27 Apr 2014 21:41
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Hey all

I hope someone with more electrical knowledge can help me out. Im trying to get the stuff together for our shower at the cottage this summer. I have a Shurflo 7.5amp pump and two 12volt 17AH batteries. We don't have solar yet so I will be hauling the batteries back and forth to charge them.

How long will the batteries power this pump? can anyone recommend a good charger. Thanks

MtnDon
Member
# Posted: 27 Apr 2014 22:25
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Unstated is the time rating for that 17 AH capacity. Alt energy battery capacity ratings are normally given at the 20 hour rate. Some other batteries are rated at the 100 hours rate.

So for arguments sake let's start with two 17 AH batteries, in parallel I assume for a 12 VDC output with 34 amp hours total capacity.

Let's also assume that the batteries will not be drawn down more than 50%. 34 AH x 50% = 17 AH usable battery capacity.

The draws 7.5 amps nominally. It may surge higher, it may drop lower depending on how hard it is working. Therefore 17 AH / 7.5 amps = 2.26 hours of use.

Due to the ways batteries work you could likely expect to get more than the 2.26 hours use as the pump will not normally run continuously. OTOH, if the pump did run constantly you would likely get less than the 2.26 hours.



If charging the batteries together in parallel look for a charger with an output = to C/10, where C = capacity in AH.

34 AH / 10 = 3.4 amps maximum.

The best charger will have three stage charging, bulk, absorb and float. You may not find one like that with that low an output.



Keep in mind that if the batteries sit partially discharged for several days / weeks before being recharged their life will be shortened.

Ontario lakeside
Member
# Posted: 27 Apr 2014 23:03
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Thanks MtnDon

That helps alot.

silverwaterlady
Member
# Posted: 27 Apr 2014 23:41
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I've been looking at portable folding solar panels to power our outdoor shower water pump and a few other things at camp. At present we are using a noisy gasoline powered pump. I would like a quiet shower. I found that Zamp Solar out of Bend,OR makes some of the best on the market at this time. Don't have the funds for this set up this summer but have saved all the info in my cabin file.
Zamp portable solar panels
Zamp portable solar panels
Charge controller on back is hinged for easy viewing and weatherproof
Charge controller on back is hinged for easy viewing and weatherproof
Charge controller
Charge controller
Padding carrying case
Padding carrying case


silverwaterlady
Member
# Posted: 27 Apr 2014 23:44
Reply 


The gasoline pump we use to pump water from the lake to our 250 gallon water tank and to pump water to our on demand hot water shower.
image.jpg
image.jpg


Sarg68
Member
# Posted: 28 Apr 2014 06:51
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I'll be curious to follow this link and see how other people are doing this. Harbor Freight has some great prices on parts to build solar powered projects. Cheers Sarg68

SE Ohio
Member
# Posted: 28 Apr 2014 08:07
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Beware the Harbor Freight solar kit controller, as they don't recommend it for 24 hour use! One is supposed to manually turn controller on and off with sunrise/sunset. I upgraded to Morningstar controller so battery can charge when we're away.

IIRC We use a 5 gallon Zodi? stainless steel tank with built-in temperature gauge with a 12 volt bilge pump. We heat the tank on the stove and remove when it hits 100 F. Drop in the bilge pump that is plumbed to a low flow shower head and flip the switch. Hot shower!

We make sure the tank is completely empty and inverted when done. Bilge pump drains by itself, no blow-out needed. No damage in freezing temps.

silverwaterlady
Member
# Posted: 28 Apr 2014 08:28
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The shower:
image.jpg
image.jpg


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