I highly doubt the SG could kill a battery. Just pure speculation though.
I've seen my SG do some funny things. One thing I noticed is that sometimes when I'm walking up to my car and hit the unlock button on my remote the SG comes on. And it is a non-factory remote unlock system.
I have also seen the SG fail to come on when I have shut the car down at a red light and then restarted. I have to push the lower right button to wake it up.
The strangest thing I've seen it do involved my Firebird. Like most cars, when I turn the key to ON, the fuel pump primes for 2 seconds. When I have the SG connected the fuel pump runs for about 30 seconds. I couldn't figure out why, I even tried changing the fuel pump relay. Finally figured out it was the SG. No idea why.