Hi Lada,
Yeah, no worries, here's another idea:
http://ghurd.info/So the controller that Ghurd came up with is not exactly intended to be a generator starter, but you could modify it to do so.
It has two modes of operation:
1) diversion load when the battery voltage is high (not what you're asking for)
2) low-voltage disconnect when battery voltage is low (similar to what you want)
So if we take mode 2, and hook up a different relay that will turn ON instead of OFF when the LVD threshold is passed, then you can use it as an automatic generator start switch.
Simple, but it would lack some finesse. One thing you would notice is that if you put on a heavy electric load on the batteries, you could pull the voltage down enough that the generator would start. This may be good or bad, depending on what kind of load it was, what the threshold is set to, and what you really meant to do. Ghurd's controller doesn't track the state of charge of the batteries, for example.
If you can live with that, then Ghurd's controller would work.