I just had this happen to me today. I have an '01 Maxima.
When I exit off the interstate from about 70mph to 0. The Battery and the brake light comes on and will stay on until I let the engine idle for 3 or 4 minutes. I was on an 8 hour trip when this happened and it scrared me...but then it repeated over and over but it was still charging and running fine.
Did you find anything out at the dealer?