i didn't downvote but 17v on a 12v battery maybe seems a bit high. I'm more used to about 7-14% over (maybe up to 14v on a 12v batt) when charged/floating but i don't use solar anywhere currently, and i usually work on 48v systems. i normally expect to see about 54v on a fully charged battery string (13.5v per battery x4) with the rectifiers running.
i also second the opinion of running an automotive PSU for this situation.
edit: i looked it up since i was curious, some "12v" solar panels can output between 16-20v, but it's recommended that you would use a charge controller, especially if you have lead-acid batteries