Pismo Squealing Sound - Bad Power Board?

One of my Pismos has developed a new tic - a little bit of "squealing" when the battery is low when replugged to power. This has happened now a couple of times and then goes away. The battery still recharges ok; it runs on power ok; the reset button in back does not seem to stop the squeal per se. Is this a sign that the power management board is about to poop out? Has anyone else experienced this? I'd rather track down a board and replace that than have it fry one of my batteries...