Solar panel problem

Scott, where are you measuring the "15 to 17 volts"?
Is the battery connected at this time?
Is the regulator positioned on the solar panel or is it positioned close to the battery?

You would be smart to run the power from the solar panel through a BCDC charger to be sure the battery is getting the correct voltage of about 14.4. Then it doesn't matter what the panels (or the alternator) gives. The battery will only get 14.4 until full then float charge.

I have a 30amp regulator on my solar panel to charge 24V batteries. The particular unit will do 12v or 24V and has a LED screen that gives all the charging data and lots more. they sell on Ebay for around $40 including postage. I have tried others though these have to be the best in my mind. If you are interested i will forward the link to the one i have. I had the same type of unit on my previous motorhome and it never let me down. Cant recommend them enough.