Hi , I’ve had the car for six years and I’ve never changed the battery, so at least six. When I got it it had only done 14,000 miles ( it’s only do 63000 now) so I doubt the previous owner would have changed the battery. In terms of diagnosis, I don’t have a read out, but I remember seeing oil pressure, airbag, throttle revs too much, there was one other but I don’t know what it was.thanks