With just six watts at the very best of times (in theory) you are
getting 0.5 amps... just about enough to charge your flashlight
batteries; maybe, (read ahead).  Then again the sun would have to be
directly overhead and don't forget sitting in the sun on your
dash-top the temperature is going to skyrocket and any temp over 80 -
90 degrees the panel's efficiency suffers.
        Best to pick up a panel that puts out 3.0+ amps (approx. 50
watts) and hide it in your roof luggage carrier.
With 12 volt solar Panels, watts and amps and volts are not an exact
formula, there is a lot of loss here. I have a 120 watt roof mounted
panel by Kyocera that maxs out at 7.0+ amps at 17 volts which is
where they operate, then with a controller cutting that to 13.8 volts
but you still only get the original 7.6 amps.
        Sorry but your six watter may actually only output about 1/4
amp, good for a set of Nimh camera batteries.
        david (dsl82westy)
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>I just bought a Sunsei solar panel that produces 6 watts... they
>have that diode so I don't have to worry about losing current at
>night... anyway... I don't really have good place to put it... right
>now its sitting on the passenger seat... so I'm wondering if I put
>it on behind the tinted side glass... how much energy will I not be
>producing.... has anyone fooled around with this??? thanks...
>
>And maybe I should have gotten the one that produces 18 watts...