Re: (ET) T105 capacity vs BB600

["Dave & Deb" <daveb drizzle com>]

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
>