[Rhodes22-list] Solar Cells, Batteries, and GPS

[mputnam1 at aol.com]

As I've mentioned before, I'll be receiving my recycled R22 from Stan in the next month or so ... and I have a question about battery power and solar cells.
 
As some background: The 1990 R22 that I'm purchasing has one solar cell and one battery (although Stan is checking to be sure there's not another battery hidden somewhere on board).
 
After much agonizing over cost, I went ahead and purchased a GPS system and a separate depth sounder.  I mainly want the GPS in the event of an emergency, if I'm sailing in unfamiliar waters in the Chesapeake, and in the event I anchor overnight.  I understand the GPS alarm can (hopefully) wake me up if my boat drifts from its anchorage overnight.
 
I mainly got the depth sounder for anchoring.  I'm not thrilled with cutting another hole in the side of the cockpit, but I didn't want to have the GPS screen be split between the GPS display and the depth sounder display.
 
Anyway, here are my two questions:
 
1) Will one solar cell be enough if its to power the GPS overnight, in addition to other power drains on the battery?  Should I spend the money to have Stan put on another solar cell (and another battery, assuming there's only one on board) in order to have a dedicated battery for the GPS (with the other battery dedicated to the radio, depth sounder, and any other electrical needs)?  I have no idea if a GPS can drain a battery overnight.  
 
2) I purchased a GPS with an internal antenna.  My plan was to mount it on a bracket that could swing into the opening of the cabin and, thus, have a clear view of the sky.  I didn't want to mount yet another instrument on the cockpit wall (there's already a compass mounted there).  But now that I think about it, if I want to rely on the GPS while anchoring overnight, should I have gotten a GPS with a separate antenna so that it could be mounted somewhere on the roof of the cabin?  That way, I can close the cabin door at night and not worry about obstructing the GPS's view of the sky.  If so, where would you mount the GPS antenna?
 
This is all new to me, so I appreciate any and all advice on these two points.
 
Thanks,
 
-Mark