Please don't be led by the popular misconception that a simple dump load controller (voltage-sensitive switch) will protect your batteries UNLESS you are also willing to accept quite inefficient use of your turbine's output.

To have reasonably efficient battery charging, the battery voltage needs to be allowed to rise to about 14.2-14.6 volts (flooded cells) and remain there for some, limited period of time. However, if it is allowed to remain there for an excessive time period, over-charging, battery heating and water loss will occur which will effect the battery lifetime.

To prevent this, you COULD set the trip point of a simple dump controller to a suitable float voltage (13.2-13.4V). This, however, would result in MUCH longer charge times to reach 100% charge, even though you have adequate wind and turbine output to charge much faster - poor utilization of turbine potential. A lot of the turbine output would go into heating a resistor.

What the simple dump controller WILL do is protect the turbine from destructive, unloaded, overspeed conditions. Please note however, that it does not prevent excessive turbine output in high wind conditions. Only a suitable furling/control  system  will do this. I prefer variable pitch and/or controlled yaw rather than the popular swinging tail which is difficult to adjust and has still resulted in numerous destroyed stators.

In my opinion, the simple dump controller does NOT provide an adequate battery charge control algorithm.

Whst's the answer to your question? My suggestion is to use a Xantrex/Trace C40 controller or equivalent, run in diversion mode. The C40 allows 12, 24 or 48V operation and provides a reasonable charge control algorithm.