u/Alone_Profession

I have a 1999 528i. Yesterday I had an issue when, while on the highway, my car died. Speedometer fell to zero and the car was off but the dash lights were still on. Thankfully someone gave me a jump and the car started. The as I was about to pull out the car started to sputter then the speedometer and gas gauge went to zero. At this point I’m sure it’s an electrical issue but trying to solve it has me stumped. I removed the alternator to have it bench tested at 2 separate auto parts stores and it tested good. The battery is roughly 6 months old. As I test the voltage at the battery terminals, I get 10.80ish and begins to drop slowly. Any ideas on where to go from here?