NiCD battery

What are VRLA batteries? How small do they come and can golf cart batteries be used on a small setup?

NiCad batteries are a poor choice for a stationary system. The way the paste works in them makes them too fussy on charge discharge depths. They really only shine when you are using them in portable situations or where weight counts or you're willing to live with low capacities for very high currents. The only useful situation I could see for them in a renewable install would be maybe a RV but even then you'd have to put up with a ton of hassles versus lead based batteries.
NiCad and Nickel metal hydride don't really fit in with renewable philosophies as they waste so much power charging and are really only good for highly portable power sources.
All the lead on the planet comes from radioactive decay of several parent elements so mining it is a bit of a pain if the parent elements haven't decayed completely so it should be recycled.