Charging lead acid battery using boost/buck converter
From everything I've seen so far with lead-acid batteries, a CV charger may not be ideal, but as long as you aren't hydrolyzing the acid (apparently at 14.4V), it'll charge itself over time. You'll likely hit the current limit on the turbine initially before current tapers off, so I guess you do sort of have a constant current source initially. The only problem is that you mention the generator provides ~100mA, which is small for a lead-acid battery... If your discharge rate is lower, I suppose it would charge. Keep in mind that certain batteries (ex. deep cycle) are better suited to this type of application.

Hopefully this helps, but feel free to request clarification if I missed something.