I came across a charger, I will post the original posters url too with is skematic when Ilocate it again.
Simply put, it is a long wire antenna, the longer the better. An automotive ignition coil, a spark plug to induce magnetic field collapse in the coil, a rectifier and a capacitor.
I know; in some ways I am skeptical of the technique but knowing what my antennas put out for static collection in snowstorms there is no reason it should not work. This is one of my projects to get done this year.
The principle is simply collecting accumulated static charge off dust, snow and rain that strike the antenna, The spark plug fires when potential reaches a certain point, and that collapsing magnetic field of the high tension side induces a current in the low voltage side; and this is using the ignition coil as a step down transformer where that high potential static that is accumulating is able to stepped down to a potential that can be safely applied to a lead acid battery through the capacitor with a rectifier to block current flow into the coil from the battery and to rectify the incoming current to ensure correct pollarity applied to the battery.
This post will get updated soon, and also updated as the working assembly is tested.