On Feb 12, 9:51*pm, Roger Mills wrote:
Eh? 30mA at 12v is 0.36 watts - whether for an hour or a week! Over a 24
hour period it is 8.64 watt-HOURS *not* watts.

Oops, typo, obviously.

So, assuming 30mA to be the drain, the question is whether or nor a 10w
panel can produce enough watts for enough hours to produce 8.64
watt-hours in a 24 hour period. If it could produce 2 watts for 5 hours,
that should be enough.

It comes down to where it is sited.
A combination of car location re house shadowing, solar transit,
located in front or rear window, angle of panel etc.

A monochromatic panel would outperform polycrystalline under overcast
skies.