Many years ago I purchased an oceanographic instrument, which was a 1m steel sphere full of batteries, an accelerometer, a system to double-integrate the signal to convert the vertical acceleration into vertical displacement, and a radio to transmit the result to shore or a nearby ship. It worked great. However, the two halves of the sphere were welded together after the batteries were connected and the radio was turned on. The owner/engineer said it would last a year then would need to be factory serviced to replace the batteries. I asked how much the annual service was. He said he didn't know, he'd never had to do it, because the buoys were run down by ships or broke free from their mooring before a year was up. He was terribly upset that people refused to buy his wave buoys unless he made them user-friendly, because he was smarter than everybody else and you couldn't trust people to service things right so his buoys might get a bad reputation. Just sayin'