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Lead acid batteries. - Page 2

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Posted by Josepi on November 7, 2009, 4:06 am
 


Acid strength does not change useful battery voltage. Plate chemistry
combinations determine that.



Posted by Jim Wilkins on November 7, 2009, 1:36 pm
 



The Nernst equation:
http://www.chem1.com/acad/webtext/elchem/ec4.html

I have a degree in that stuff and still can't claim to really
understand it.

jsw


Posted by spike on November 8, 2009, 12:08 pm
 

Jim Wilkins schrieb:

just try it. i believe in your abilities.

it is usual that that "science" stuff is written in a highly complicated
way, that people drop it before they begin.

ehm yeah i made a mistake, more acid in this kind of battery will lead
to more AMPS, the size and arrangement of the plates drives VOLTS.
(correct me if i am wrong) you could try layering the materials...

"Science is a perversion of itself, unless it has as its ultimate goal
the betterment of humanity." Nikla Tesla

Posted by harry on November 8, 2009, 8:24 pm
 


Each cell has an almost fixed voltage. You get more volts by
connecting them in series.  (In the case of lead acid cells, it's
2volts/cell.)
The bigger the plates in area exposed to electrolyte, the lower the
internal resistance and the higher the current (amps).
The term battery is actually incorrect, this is the collective noun,
it is actually a "battery of cells", each acid container being a cell.
Car batteries of course have six cells in series to get the twelve
volts.
"Heavy duty"  batteries have lots of thin plates in each cell, hence a
large area & can deliver a high current.  They don't last as long
though.

Posted by Jim Wilkins on November 9, 2009, 1:03 am
 


I do, I work in electric vehicle R&D. The manufacturers don't reveal
the most important and sensitive "trade secrets" of battery
construction or chemistry, just as Coke has protected its secret
recipe for far longer than patents last.

The voltage is influenced by the concentration of the reactants,
including the acid (pH) to some extent. That's why the voltage drops
as a cell discharges. The Nernst equation gives a quantitative handle
on that if you know the concentration right at the plate surfaces,
which is hard to measure.

Lead-acid is pretty well understood and explained, compared to
Lithium.

jsw

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