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