"Unlimited Current" is limited by the current the relay can handle.
There are some ghurd controllers handling over 1200W.
A relay based system is not likely to handle 100A of 12VDC long if connected as shown in the original post.

I do not recommend my controller with power such as 1200W.  A system that size would generally benefit from a superior 3-stage temperature compensated factory made controller.

The controller shown in the original post has some serious issues.

First-  If you can not figure out the parts shown in the schematic and know how a power mosfet works, it will likely cost more than a factory made controller if ALL the parts costs related to building it are considered (S&H from a couple places, PCB chemicals and boards {and their extra 'hazardous materials' S&H}, etc).

Second, A & B -  It will be nearly impossible to get the size of the dump load correct.

A- If the dump load handles too small a load, the windmill runs away because it is severely underloaded, resulting in breaking off blades and other catastrophic failures.
Easy to find info about run away windmills and broken blades.

B- If the dump load handles too large a load, the windings will burn up in a good wind, and a good wind is when the system will be dumping.
That is something that does not get mentioned too often, because not many people think using that type of controller is a good idea.
The concept is roughly the same as the Oatly controller kits which do things like this,
http://www.fieldlines.com/story/2008/11/8/63523/3798

Third- The bioelectrifyer controller was not really very good at the time.
It could have been good with just a few tweaks.
Anything that for the control operates relays, slow enough to not kill the relay, is pretty much by definition, NOT a good controller.