my parents use a inverter battery system and are looking for a good generator to charge the batteries. something that knows when the batteries are low and turns itself on and off, iv been looking at a 10kw propane generac standby but i'm not sure it will turn on and off
10KW is pretty large for just topping off a battery bank. I use a remote start Champion 3500 connected to a Snap-On 100 Amp auto shop battery charger and it usually tops off my battery bank in less than 30 minutes of run time. I have to use the remote to start it though. It's still nice to stay in bed and hit the remote to run the furnace until the sun comes up to take over.
Try looking at some of the off grid companies that provide complete integrated systems(solar, wind, water driven with generator backup). Many of them sell the individual components including auto start units that can be used on various generators. Try to find something compatible before you buy the generator.
Try these sources: New England Solar Electric, Powertap Inc. (www.amplepower.com), Wind & Power Inc., Jack Rabbit Marine