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shawn

Senior Member

Joined: 30/03/2010
Location: New Zealand
Posts: 210

Posted: 04:19am 26 Apr 2010

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Have just bought 12 2 volt 1000 ah gel cel batteries I have not worked out how many amp hours I need yet my power use is small one f&p wash a day small fridge/freezer and a few house lights. wanted to go 48 volts but that would mean 24000 ah with these batteries can a bank be to big? they came off the telephone system last month nothing wrong with them just routinely replaced.

VK4AYQ
Guru

Joined: 02/12/2009
Location: Australia
Posts: 2539

Posted: 03:39pm 26 Apr 2010

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Hi Shawn

That's a good battery bank and 24 volt is a good compromise for the system you are talking about.

You will need to get yourself a little power meter off ebay and check the power requirements of all appliances you will use, then work out the watts daily usage of all of them to give you an idea of your daily usage. It is recommended that you add all usage for at least 3 days and this amount shouldn't be more than 60% of your battery capacity, in your case 24000 watts total X .6 = 14800 watts and a power input to be 10% MORE than that. 15300 watts approx over three days or so, for a full capacity system you will need to put that amount back in to the batteries at least.

Obviously the more power you can save the less power you need to put back in but the 10% extra is needed to overcome system losses.
You can do an estimate on the PV cells and wind input based on that figure.

I have found the fridge is the major power user so you may consider buying a new high efficiency fridge as it will work out cheaper in PV cells to run it rather than an old low efficiency one. A five thousand watt 24 volt sine inverter would handle the load OK if you have no pressure pump. Sensible use of appliances used at once is necessary.
In my case I have replaced an old fridge using 4000 watts a day and a freezer using 2400 watts a day with a new 2 door combination using 1800 watts a day.

Led lighting and entertainment system is a good idea to have separate from the main drag. as this load is minimal it can be run on a 12 volt system with a couple of 12 volt panels. If you use a pressure pump there is some 12 or 24 volt ones on ebay that do the job very efficiently.

Hope it is some help

All the best

Bob

Foolin Around

shawn

Senior Member

Joined: 30/03/2010
Location: New Zealand
Posts: 210

Posted: 05:18am 27 Apr 2010

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Thankyou for your time Bob I will take your advice and do some more homework.

davef
Guru

Joined: 14/05/2006
Location: New Zealand
Posts: 499

Posted: 10:22am 27 Apr 2010

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Are there more available? In the South Island?

Cheers,
Dave
Chch

Pukwudji
Newbie

Joined: 10/07/2009
Location: United States
Posts: 20

Posted: 01:42pm 12 May 2010

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I think you're math is off. 12 - 2v 1000ah batteries wired in series to get 24v would not be 24,000ah, it would be 1000 ah. When wiring batteries in series (to increase voltage) amperage does not change. You can either wire batteries in series to increase voltage or wire them in parrallel to increase amperage (or a combination of the two). If you were to pull 24v 100amps from this bank it would be pulling 100amps from each of the connected 2v batteries to make the 24v 100amps required by your draw.

For instance if I have two 12v batteries rated at 100ah, I could wire them in series to get 24v 100ah, or I could wire them in parrallel to get 12v 200ah.

If I had four 12v 100ah batteries I could wire them in series for 48v 100ah, in parrallel for 12v 400ah, OR I could wire them in series and parrallel (two groups of two) to get 24v and 200ah.

Don't freak out, because 1000ah at 48v is still a lot of useable power. That is a respectable bank of batteries. I'm jealous as I've only got two 100ah 12v batteries collected so far.

-Brian

-Brian V
Hillsboro, OR (USA)
KF7DUZ

shawn

Senior Member

Joined: 30/03/2010
Location: New Zealand
Posts: 210

Posted: 07:21am 13 May 2010

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Thankyou Brian I am keen but very new to all this (shoe horses for living) and before I started hardly new the difference between ac and dc so have spent ages in these 4ms learning have built new mill short of blades do them saterday, bought bat bank,puting truck alt on small petrol engine, have no invertor yet open to suggestions need about 3kw ofgrid also have no charge controller somthing off the shelf am putting gordens cap mod onto mill so 3 phase will already be rectified to dc.

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