A customer of mine who has a large power vessel also has a small center console he uses for Striper fishing. While I was working on his big boat he was lamenting that he can't seem to keep batteries in his center console for more than a season.
I told him I would stop by the next time I was in the anchorage and this is what I found. This was a 10W panel plugged directly into a 12V outlet under the center console, which then fed directly to the battery.