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Author Topic: what's best for 24v 200ah solution 4x100ah or 2x200ah ?  (Read 1691 times)
fc
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« on: July 07, 2009, 11:10:48 AM »

Hi I'm building a system where i still defining the battery capacity but all is pointing to 400ah to keep a utilization of 50/60% of batteries.

Now i have big doubt, what is best and why

2x 12v x 200ah serial connected or  (2x12vx100ah serial)x 2 parallel connected ?

my system will be a hybrid system with an 500w wind turbine +  2x 130w solar panels.

thanks a million
?

 
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Justme
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« Reply #1 on: July 07, 2009, 12:10:29 PM »

Could you supply actual usage levels as I am concerened that you are planning on using 4.8 kwh per day & so would need nearly 19 hours of FULL output solar to just keep up never mind losses & EQ charges. Or you would need nearly 10 hours of full output wind / day.
 Even mixing the two your usage is larger than your likely charging capacity.

Is your 50-60% usage for more than one day?

On the subjest of bats my thoughts are

1, The larger bats should be cheaper per ah
2, the larger bats will have less interconect cable to buy
3, the larger bats will have less system losses due to the fewer connections (cable to terminal & terminal to battery)
4, the smaller bats will be lighter to carry (but more trips)
5, if one fails then cheaper to replace (but if one goes its likely they all need to be replaced)
6, consider your site for space, weight & shape, it might make a difference.
7, is 4.8kwh realy enough? have you allowed for no power days in that? You should look at about coping for 3 or more days with NO charging power from sun or wind.
8, have you considered forklift bats?

We use less than 3kwh per day & have a bank of a theoretical 18.6kwh (but only 50% usable to 50% SOC / DOD) (1550ah at 12v so the same as 775ah at 24v) so roughly 3 days worth to 50% 4 at a push. These number crunch's actually match our real world performance when in winter we get 3 days between running the genny as we get little solar & wind of any worth.


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Navitron solar thermal system
30 x 58mm panel 259L TS
1200watts solar 120vdc
FX80 Solar controller
2 x Victron Multiplus II 48/5000/70
Cerbo GX & GX 50 touch
BMV 700
6kva genny
48v 1000ah
Grid Possibly coming soon
fc
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« Reply #2 on: July 07, 2009, 12:23:42 PM »

what i will use :
server 150w 24x7
lights  250w  4hours day

thanks for the input.

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Justme
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« Reply #3 on: July 07, 2009, 01:10:56 PM »

WOW thats a concise list lol


You have a problem then.

You use exceeds you charging capacity unless you are going to use mains / genny as well.

You also have no allowance for days with no power or that the batteries are not 100% efficient when charged. You need to allow about an extra 20% for charging losses. So your 4600wh becomes 5500wh (5.5kwh) per day.

With 3 days (and if this is mission critical stuff then think 7 days) of no charging power you need 16.5kwh available so a bank of 33kwh, thats about 1400ah so your 400ah is just not going to cut it.

Will you have other power sources for charging the bats?
The solar will give about 8 hours of full output in summer & 1 or 2 in winter so 2kwh in summer & 0.260 - 0.520kwh in winter. The wind is harder to quantify as each site is very specific.


I am sure other opinions will be along soon.

Justme
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Navitron solar thermal system
30 x 58mm panel 259L TS
1200watts solar 120vdc
FX80 Solar controller
2 x Victron Multiplus II 48/5000/70
Cerbo GX & GX 50 touch
BMV 700
6kva genny
48v 1000ah
Grid Possibly coming soon
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