Accumilator issues

About 2 months ago my brakes would make various noises when applied. Sounded more mechanical then anything else but my brakes still worked. We are retired so only put maybe 100 to 150 miles a month so not a lot. After about 4 or 5 weeks I took to dealer to checkout. They called me and said they were getting weird volt readings so had to replace battery. The following afternoon We were informed that the accumiltor needed to be replaced at a cost of $3500.00. Since we have another vehicle didn't need to get fixed for now. My question is we have still driven the same amount and it has not made any noise at all since we got it back. Concerned and confused and wondering if battery could be the initial culprit.??? Any idea's from anyone.

Thanks
Charles