Regarding gel cells, there are some that are made for automobile use.  
They are just like the old lead-acid, in that they are 12 volt and have 
the same terminal set up so you can just swap them with your current 
battery.  They also make an excellent interior battery for using when 
camping, since they don't give off any toxic gases.

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Craig Standley				1974 Volkswagen Westfalia
University of Washington
Physics  				"Life is like riding the bus, it 
cstand@u.washington.edu			 requires change." -Dennis Miller
http://weber.u.washington.edu/~cstand    
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