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Second Battery Installation Question: Is an isolator required?

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Option 5:   Replace your factory vehicle Alternator for a High Output Alternator (lots of them on the market). 


As SnowDrifter explained the issue is the massive bursts of ampere draw whenever your music hits a peak (Kick Drum for example).  Your factory alternator doesn't produce enough Amps to supply those instant current draws so you end up draining it from the battery, which in turn lowers the voltage of the entire electrical system of your car.  Upgrading the Alternator Capacity is the best solution to that problem.  Second batteries can work for sure, but in reality your still overdrawing on the Alternator and affecting the entire vehicle electrical system.  All the 2nd battery is doing in that scenario is removing the visible affect of the lights dimming.  But it's still putting a strain on the Alternator almost certainly lowering its lifespan and could cause other electrical issues. 


There are two ways to upgrade how much electricity your generating.  Add a second Alternator as SnowDrifter mentioned, or replace your existing factory part with a significantly more powerful aftermarket Alternator.  The second option is, IMO, a much easier solution.  


Multiple Alternators are an absolute necessity for people running Monster SPL Systems.  I'm talking anywhere from 4,000 Watts to 20,000 Watts!  But for what I'm hearing I don't think you need that.  And honestly, I'm not convinced you even need a 2nd battery.  A 300+ Amp Alternator will solve that issue.  I WOULD however Also Upgrade your main battery along with the Alternator since all that massive amp draw is still flowing thru it.  Factory/store batteries weren't made with that kind of usage in mind.  The Autozone batteries will function, but they won't give you the best results, and likely will have a lower lifespan with that much power flowing thru them consistently. 



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