As a general rule of thumb, don't use a deep-cycle battery (like the optima yellow top) for the car'* main battery. Use an isolater and run it only for the stereo, with an optima red top or other standard automotive battery for the main vehicle battery.

A deep-cycle battery can put an incredible strain on your charging system.

Will it kill my alternator? It'* got a lifetime warrenty on it, so I'm not too worried.

Actually the acquisition of the yellow top helped alleviate some of my initial woes.
The resistance of the batt seems to love taking a quickER charge, but then again, I can see your point on the deep cycle side. More power density requires more replenishment (so the math goes). Any recommendarions on a good isolator?

BTW, all I wanted was a smaller pulley. LOL. Thanks for the help here.

My suggestion is to get ahold of speedguy........and get one of his better alts. The smaller pulley will only kill your rear bearing faster. Ty'* alt'* are beefed up internals, beefed up rear bearing, and smaller pulley.

Then get a red top for the car, and isolate it out to your deep cycle. You're probably talking a 200 amp alt, not the 160 I'm running.

I've already got the aforementioned beef, yet only about 180A. Not to mention a 2.250" pulley. But it sounds like Speedguy would be someone to talk to.
Thanks for the info.