Well I bit the bullet and upgraded the motorcycle battery Honda put in the 2008 Accord.

I went from a 51R type battery with 450 CCA to a Marine battery (part #M24-3) I bought at Advanced Auto.

I barely had enough room for the new battery and had to buy a new battery clamp but it worked.

I'm now at 800 CCA. I also did the Big 3 upgrade.

 

Cool... I was skeptical about the motorcycle battery too, but kept it in there (2003 Accord & 2007 Civic). Didn't have any problems but no big aftermarket stereo either. My daughter finally killed her battery by leaving the lights on overnight for the 4th time (84k miles too).