I wouldn't worry about a regulator for a 10 watt solar panel, however you
without a regulator, you should have a diode to prevent the panel from
discharging the batteries when the sun goes down.. If you end up with more
than one panel, you need a diode between panels to prevent problems if one
panel get shaded while the other has full sun. Just bare in mind that each
diode will drop the panel voltage about a half volt.

I'm running two 56 watt panels and a Windbugger wind gen. Neither has a
regulator.. However I'm charging a 800 amp/hr battery bank..

(Just as a side note. Once while working on the DC circuit, I turned off all
batteries but noticed that the frig was still running. Turns out I had
neglected to turn off the solar panels and they were running the frig
directly.)

Steve
s/v Good Intentions