The best answer for this depends on a couple of details.
Like:
Do you have access to AC power at the storage location?
Is there a roof over the storage location?
Attaching a solar panel to an RV cover doesn't sound like a good idea to me......unless maybe that "cover" is an actual roof.
P.S. Any charger you leave connected to it should be an automatic one and not the "dumb" trickle variety.
'07 Damon Outlaw 3611
CanAm Spyder in the "trunk"