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TheBearF8

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Reply with quote  #1 
In a Grid Tied with Battery bank

Assuming Lithium-ion  batteries  (thou I don't think it applies/impacts the questions?????)

lets say 24V 800AH  as a battery
When I use the term/word configuration :: I'm thinking specifically series and parallel connectivity

You can have 1 battery             24V 800AH in  1s1p configuration  
You can have 2 batteries    2 x  12V 800AH in  2s1p configuration
you can have 4 batteries    4 x   6V  800AH in  4s1p configuration
you can have 8 batteries    8 x   6V  400AH in  4s2p configuration

All are 19,200Wh  or  19.2kWh   ( ? capacity ? )

(1) But, which is better?  Is there any impact when comparing configurations
     is a single 1s1p configuration better/worse than 4s2p or even  8s8p (using 3V 100AH)

(2) Which lasts longer? If the capacity is sized to last 8 days so average draw from the battery bank  2.4 kWh per day and so most of the time you are always just topping up.

(3) Is there any maintenance or management issues to consider when comparing configurations

(4) Does configuration have any impact at all ?

Thanks in advance

Rick H Parker

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Reply with quote  #2 
All are 19,200Wh  or  19.2kWh   ( ? capacity ? )

Yes .. If and only if, the amp-hours you listed are per parallel string not per battery.

But, which is better?

One 24V battery, less to go wrong.

Is there any maintenance or management issues to consider when comparing configurations

The more complex any system is the higher the maintenance. Managing more of anything is always a bigger issue.

Does configuration have any impact at all ?

Redundant question.





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Rick H Parker
Kansas, USA
Electronics Engineering Technologist
stmbtwle

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Reply with quote  #3 
One series string if you can do it. 4-6v are probably better than 1-24v, as if one fails you don't have to replace the whole set ($$$). With parallel strings, if one string fails it can/will pull the other strings down as well, and you may not detect it immediately. Been there.

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Rick H Parker

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Reply with quote  #4 
Mixing new batteries with old batteries is a no no.
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Rick H Parker
Kansas, USA
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stmbtwle

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Reply with quote  #5 
Not the best but sometimes there are other considerations. In a series configuration probably not as bad. I suspect that's why they sell 2v cells.
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TheBearF8

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Reply with quote  #6 
Thanks all

Does the configuration impact the life length , or longevity of the battery?
I know there are differences between sealed and flooded and so I'm sure there would be a difference between lead acid vs lithium ion
but sticking with one type.  With a predominant trickle charge scenario does the configuration have any impact ?

Let me clarify  predominant trickle charge  If my Solar panels were able to produce 5 Kw and the Battery bank had a 50kWh capacity and the draw was around 4 kWh per day
Thus solar panel supply is equal or more than daily need, and the battery bank is purely for non solar hours (night time) and should the grid fail (hurricanes, etc..)

Would the configuration have any impact on the life length  (or some other impact/reason) of the batteries

Thanks again to all
Rick H Parker

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Reply with quote  #7 
In a series configuration probably not as bad. I suspect that's why they sell 2v cells.

In series the old and new would not charge evenly due to the difference in amp-hour capacity, amp-hour capacity drops as a battery ages.  The new would charge slower and always be under charged . The old ones would charge faster get over charged waiting for the voltage of the new one to come up.  In short: When you mix old with new in series your mixing different amp-hour capacities .....

They sell individual cells so that any voltage banks in multiples of 2V can be done. The manufacture does not need to produce and stock a zillion different odd voltage and low production batteries.

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Rick H Parker
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stmbtwle

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Reply with quote  #8 
I'm not arguing that mixing cell ages is better or even good, but sometimes it IS done, probably for financial reasons. There have been a couple discussions about using cast-off batteries.

I think another reason for 2v cells is weight.

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Rick H Parker

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Reply with quote  #9 

There is one advantage of using multiple smaller batteries over fewer large batteries. The thermal pathway in the smaller batteries is shorter resulting in better heat dissipation. This may help in keeping the peak temperature down and extend the lifespan of the batteries.

You talking about the 2V traction cells used in heavy industrial electrical such as forklift battery banks? Those things have positive tubular plates and negative grid plates, which results in higher capacity and longer life than the conventional batteries with flat plates.

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Rick H Parker
Kansas, USA
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Reply with quote  #10 
Yes cooling would be advantageous with individual cells especially if a space were left between them.

And 6 or 12 large cells would be easier to install than the same capacity/weight in a single battery.

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Solar is like the wind. It may be free, but putting it to work isn't!
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