Mine beeps at me A LOT. Of course it's not a toyota alternator.
It is annoying as hell I think and I have gotten used to starting it and immediatly silencing both alarms.
Ipersonally think it is set too low but I have no idea how to change that. I don't think I have every actually confirmed that it was charging at the rate it is supposed to alarm at.
I am tempted to just disable the beeper or just give it some sort of labotomy since I think it serves me little purpose other than just to freak others out who drive my truck.