Re: (ET) T105 capacity vs BB600

["Bob Murcek" <rmurcek geisinger edu>]

Somewhere in this thread I think I heard someone mention fan cooling. 
It just occurred to me that it would be really risky if the fan's motor
had brushes!  I would think there'd be a good supply of brushless fans
in the surplus market.

>>> "Dave & Deb" <daveb drizzle com> 7/11/2005 12:05:07 AM >>>
interesting.  thanks for the battery lesson!!
Dave

>> Ok I gotta finally ask.  what are flooded NiCd's?  I know what
NiCd's
>> are,
>> I am quite familar with flooded lead-acid and I always thought
"flooded"
>> refered to being "wet".  Are thes NiCd's wet??  Does flooded mean
>> something other than what I've thought all these years??
>
> Basically they are batteries that have plates made of nickel on one
> side, cadnium alloy on the other, seperated by a thin membrane.
> Permeating this membrane is a solution of 30% potassium hydroxide
(KaOH).
>
> All nickel cadnium batteries have this set up, however on the little
> batteries the KaOH is in a paste type solution between the plates
> (sintered plates). Problem is when the paste dries up, the battery
is
> dead. In a flooded battery, you just add more water.
>
> Comparing a "normal" NiCD to a flooded NiCD is kind of like comparing
an
> AGM battery to a flooded golf cart battery. But not quite the same
> because of the chemical reactions that happen during charge and
discharge.
>
> In NiCD and NiFE (Nickel Iron) type batteries the positive and
negitive
> plates never change state, they only exhange ions across the
membrane.
> Likewise the KaOH never changes state either. It's always 30% KaOH,
thus
> measuring the alkalinity of the electrolyte will tell you nothing
about
> the state of charge. The advantage to all of this though is that
they
> last a long time. Apparently NiFE batteries made for the 1900 series
> cars are still running today. You just have to replace the membrane
(pig
> intestine in old NiFE) every N number of years. The plates don't
really
> degrade, they never really change state.
>
> In lead acid batteries by comparison the plates go from Pb to Pb
oxide
> and back and the electrolyte goes from H2SO4 to H20 and back again.
> Chemically they change state, and over time they degrade.
>
> NiCDs have their own problems (they gas during charge, the membranes
can
> break down over time, they heat up if you're not careful, ) so you
can't
> be totally ignorant about them however they seem to last a lot
longer
> than lead acid.
>
> Chris
>



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