That reminds me of a funny story. The windmill I built worked well in medium and high winds, but did nothing but spin idly when the wind was low. Still, that's (a little) energy that you could capture in theory but it simply did not have enough voltage to get over the battery terminal voltage which makes it impossible to charge the battery.

But a windmill is mostly coils and magnets and when you short it it actually will charge the battery, briefly robbing the blades of some momentum. So, if you periodically short the coils using a bunch of powerfets and an oscillator you can charge a windmill in low wind conditions that would otherwise do nothing.

So far so good. Built it, tested it, worked like a charm. And then one day I decided to temporarily decouple the windmill from the switchboard, but I had forgotten about that little booster. FOOM, instant fire on the booster board after I pulled the switch. The FET circuitry and the oscillator had happily continued to work on the power provided by the windmill, and had allowed the end stage of the circuit to reach a very large multiple of the voltage that it normally dealt with because the battery kept the voltage pegged to a maximum of about 48V!

Needless to say that led to a somewhat more robust V2...