What he said. The battery that comes with this car is already AGM. You're going to have to spend real money to get something notably better. And OPTIMA isn't better, by the way. Not anymore. When they moved production to Mexico, their batteries started to SUCK. Before that I always used their batteries. I went to Sears Platinum batteries which were far better, but of course they stopped selling those. So now you gotta get like XS Power or something similar from an audio shop.Check for grounding issues first, then upgrade your alternator