What kind of battery do i need

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Old 07-01-10, 11:37 AM
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Unhappy What kind of battery do i need

Hi,

I have a little system in my home that uses a 5W pump and I want to make it solar powered.

I have a bunch of solar cells that I got off of ebay (0.5V 3.6A 1.8W)

My plan is to connect a couple of them together to get enough wattage for the pump. Then connect this to a 12V battery. Then connect to the battery to a 12V DC to 120V AC car inverter (or other, if better, please suggest) which the pump will be plugged into.

My question is, what kind of battery would be best and cheapest for this task? The pump runs 15 min on and 15 min off at MOST. Of course, when the sun sets, the battery will have to power the pump until the morning. What type and specs do i need? i.e. lead acid? lithium ion? 0.5Ah? I really don't know what I'll need.

Thanks so much.

Mark
 
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Old 07-01-10, 12:55 PM
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A small marine deep cycle. BUT If that pump ran 12 hours per day 365 days a year it would only cost you $2.50 plugged into the wall.
 
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Old 07-01-10, 10:04 PM
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Originally Posted by mcircus View Post
A small marine deep cycle. BUT If that pump ran 12 hours per day 365 days a year it would only cost you $2.50 plugged into the wall.
Haha, that's a good point. But this is not to save money. Would Nickel Metal Hydride work?

My plan is to get 10 1.2V NiMH batteries for $1.25 each and wire them in series for 12V. Then attach them to a 12VDC to 120VAC inverter that the pump can plug into. Since the batteries will produce 12V I shouldn't need a charge controller.

My concern now is how to wire the solar cells up to the batteries. If I wire them to the battery bank in parallel, will the voltage remain at 12 V? Will this harm my solar cells? Will a diode help?

I'm a noob, thanks for any and all advice.
 
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Old 07-06-10, 01:04 PM
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The RV/boat folks do this kind of thing all the time. You'd need to hook up your solar cells to a charge controller that keeps a battery or batteries charged. You then run the pump off the battery/s. RV's typically use 12v deep cycle battery banks or two 6v golf cart batteries hooked up in series to get 12v. If your pump is 120v AC you also need an inverter to change the batteries DC current into AC. Better to get a DC pump if you can. No inverter that way.

The 6v golf cart batteries can withstand more deep cycles than normal deep cycle batteries can but are more expensive. The charge controller is necessary because the solar cells can overcharge the batteries if connected directly. As I understand it, the controller allows the solar cells to charge the batteries then burns off the extra cell output as heat.
 
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Old 07-14-10, 01:01 PM
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For that small system, I'd get an AGM battery, or better, golf cart type batteries, maybe a 55AH for AGM. You could use it for other things as well.


If each cell is 3.8A at .5V, you would wire 24 in series to 12V at 43.2W

You will need a charge controller, or at least it is highly recommended you get one. My charge controller just opens the cell from the battery (a Sunforce 7A one, connected to a 15W panel, charging a 35AH AGM battery).

For just that pump, all you need is a 15 to 20 watt panel, a 12 or 18 AH AGM type battery, charge controller, and motor logic controller, and use a DC pump.
 
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Old 07-14-10, 06:48 PM
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Batteries

Dont' Think Your Going To Pump Much After Dark. Those Little Batteries Don't Have The Amp/Hours Capacity. Go With The Deep Cycle Type.
 
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