What Gary and Fokion are saying is very true. The Alternator needs to exceed the load condition but the battery only needs to start the engine and run the lights(or listen to the tunes) with the engine off.

In fact, I ran my Sportage for a couple of months with only a 5AH battery.

Ron Schroeder
Long Island NY
99 4DR auto Sportage, 30x950R15 tires, 3/4" strut spacer, rear air springs, Manual Hubs, FRONT Torsen LSD
00 Safari AWD, 2" lift, 30x9.50 tires, 4x4 conversion in progress
73 Pinzgauer Swiss Army troop carrier