battery size help

[LivingstonII]

hello everyone, I've gotta a question about battery sizes. but first i just want to say i'm new here and new to bikes. i purchased my first bike in Feb. its a 1978 xs1100e standard. i didnt know anything about the bike other then it ran well. i found this site and started my research and i cant believe the potential of this machine. anyways my question is my battery is dead and its one of the maintenance batteries so i decided i wanted a sealed mant free battery so i was on the local classifieds and ran into one listed. it was listed as a x2 power batt new. batt # x2-18l. sure enough i looked it up and it says its a fit. now it retails for $115.00 and the guy only wanted $40 for it. well i picked it up and it turned out to be a x2-20l. now they are both for motorcycles and they both have the same voltage. the 18l size is 8.13"x3.56"x6.38" and the 20l is 6.88"x3.44"x6.13", so that's about 1.25"x0.12"x0.25" smaller from what i should have in size. now the only other difference is the capacity and CCAs. the 18l is 20AH capacity and 330 CCA and the 20l is 17.5AH capacity and 310 CCAs. so i would like to use the 20l if i can but i don't want to install it if its not going to work. i have the option of returning it so i don't wanna use it if i just need to buy the right battery size and capacity. thanks for the help.

[crazy steve]

The smaller battery will work, but will have to work 'harder' due to it's lower AH rating, so don't expect a long life.

As to the difference between 'sealed' batteries and the older non-sealed ones, don't sell the less-expensive older style short. Properly activated and maintained, I've seen 6 years or more service life from these while the so-called 'better' sealed ones have rarely lasted more than 3 years....