109,000 miles and new battery needed :(

D***! My luck. If I had lived in Ca the warranty would have been 'til 150,000... anyways, all the lights came up yesterday. brought it to the dealership and lights magically went away. They performed a history on my baby and one of the cells was dying but he said no worries, it'll last a while longer. Except today all the lights went on and acceleration was experiencing difficulty so looks like I'm possibly out $3-$4K. anyone have experience with replaced batteries? I love that there is a 12 month warranty.. oh, totally being sarcastic. I've never had to deal with this car like this before and am ready to cry. Is this normal to dump this much money in the car? I feel like I'm not really saving... just had to replace something else a couple months ago for $500.