I have a 1500watt aftermarket audio upgrade and I'm wondering how can I do big 3 upgrade since the battery is located in trunk? Any info or pics would be greatly appreciated

 

Short answer is you probably don't need to. 1500w isn't that much really, assuming you're talking max, not rms, and because the battery (and factory fuse box?) are right there, just use a decent wiring kit and you'll be fine.
You don't need to worry about upgrading the alternator wiring either. The factory wiring is fine, and the battery is doing all the hard work, not the alternator, so again, it's the wiring to the battery that is the most important.

 

Yeah you don't need to worry about the alternator wiring unless it's been damaged. I had my audio system upgraded w/ similar amperage & new head unit, amp,cabin speakers & subs etc. The shop just used a good grade amp wiring kit & of course new speaker wire etc.

 

You may want to consider a good quality capacitor to help the alternator on sudden high peak current draws.
On my XJS I have a 977 wrms system and I help it with a 2 farad cap, although with classical you don't necessarily encounter so many highly demanding notes.
On my XJR I have a similar system but I have not added a cap and, apparently, don't miss it.

Cheers

 

I'm going to politely disagree here. A Capacitor is almost always completely useless. If you are having voltage drop issues then the cause is your battery, and you should remedy this.
Using a capacitor is the equivalent of cutting your leg off and trying to stop the bleeding with a band-aid.
The batteries in our cars are quite large to start with, and I would be very surprised if anyone here is running anything big enough to stress it. Myself included, and I'm pushing 3000wrms.



disclaimer: my system is the definition of overkill, and even with the music turned up I'd be lucky to be using a third of it's capacity

 

Plus tweeter amp under the battery

You may be right, although the principle here is quite basic: You have instantaneous high peaks where the system may not necessarily have the full amount of instantaneous amps to cover the full demand. I have heard many times from people whose dash lights flicker with amp-demanding musical notes. I'm sure that a cap would resolve that problem, although I do believe, as well, that a review and optimization of those cars electrical systems will achieve similar effect. With the type of music that I listen to I may not have more than 10 cases (out of some 300 or more hours of music) where music notes may demand my system's top supply capacity. Like I said before, on my XJR I have a similar sound system with no big cap added and I just don,t perceive any difference. The caps don't look bad, though....

 

I'm from the old school where as you don't need a cap unless your lights dim on heavy bass notes @ volume lol.