While the most common dump controllers do indeed seem to dump
battery output, likely because this is convenient, easy to understand and one controller will do a multitude of sources, I don't (personally) believe it to be the best solution.
My own wind turbine, for instance - while there is a battery voltage sensing circuit (as in your typical dumpload controller), and it has hysteresis (like many of the typical dumpload controllers do), the actual "dump" part dumps the 2KW turbine into a 3-phase dumpload at the AC SIDE.
This has several advantages as I see it.
- It's much easier on the rectifiers
- It's a more efficient control with less points of failure
- It completely avoids the problem of "over-dumping" the batteries, as may
happen for example, if you are only just getting too high on your battery
voltages. If you have (say) 500W going into your batteries, they could get
high enough to trip the dump - but if your turbine can make 2KW, then you
probably need at least 2KW dump - which will be very tough on the batteries.
It's quite easy to achive battery monitoring with "wild-side" dumping, many of the dumpload controllers presented here over the last few years are readily adaptable to this method of control (especially those that merely operate a relay)