you just replaced the battery - was the battery terminals tightened properly? was the new battery charged up before the install?

just because it is a new battery, it means nothing - it still can be defective right off the shelf, i had that happened to my E39, ran for a couple of weeks and then died... the autozone or whatever the chain was, confirmed the new battery dead beyond repair, and i got a new one...

check the battery connections, and check the battery itself...