I woudn't say you've been ripped. You have a great battery and if your lights are still dimming then any battery you would have bought would have done the same. The big 3 upgrade mentioned above holds some truth to the charging system. Any resistance taken out of the 12v equation can help big. Give that a try. If your still not satisfied have you thought of adding a second battery? I as well as several friends havent had any luck with capacitors and the money spent versus just adding a secondary battery. It just works....period.

By the way how many amps/watts are you running in your system and what guage and length power wires are you running to them?

 

I'm running a kicker 750.1 and one 12" CVX. 4 ga wire. The length is not very long at all considering I have the amp behind the back seat on the same side as the battery.

I'll try out the big 3 mod soon and hopefully that will help.

 

That should help but a 750 watt amp even if its only powering one sub can still pull some amps. The 4ga wire should be just fine as long as you have a short ground cable. What kind of dim are we talking about after the battery upgrade? Similar to a power window being rolled up to the stops? More/Less drastic than a power window?

 

the dim is fairly drastic... the volt meter jumps down atleast 1-2, maybe even 3 volts when the sub hits

 

you need a capacitor!! your draining you charge. maybe 2 of them.