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Need help with decision-2nd Battery, or new alt.

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  • Need help with decision-2nd Battery, or new alt.

    Hey guys, I have a dilemma. I just bought 2 Pioneer 3002 SPL's which run at 1000rms each. So I don't go completely broke, I am going to get two amps to push 750rms at 4 ohms each. I don't know if my stock alternator can handle that since I'm 99% sure my stock alternator on my Subie pushes 75A. This probably won't be enough since the total power would be around 1500W. Using the equation Power=Voltage X current, we get 1500W= 13(ish) x current. Therefore, I get about 120amps. So here is my question: even with a die hard deep cycle battery and both amps having their own 1 farad cap, it would seem like I need a new alternator, correct? Those run about $350 (at least the ones I could find). Does anyone think I could get away with installing an even better battery, like an Optima Yellow top? My other option is to try put a 2nd battery in my trunk, but for all the pain/hassle, I'd rather almost go with getting a new alternator. What does you guys think? Thanks in advance for any help.
    CarPC: 100%
    Software: 100%
    Amps/Subs: 0% (on hold)
    Fabrication: Need help!!! Someone in Boston area who can help me with this please send me a PM.

  • #2
    thread moved to car audio.

    if you don't have an alternator that could charge two batteries, it doesn't matter if you have two batteries or not.

    I would upgrade the alternator first, then add a battery later...that is if your alternator is as weak as you say it is. I would also upgrade your stock battery with a deep cycle while you're at it.

    In this game, you've got to pay to play. You cannot just slide by the seat of your pants...else you're not really getting your money's worth if you're not getting your performance worth.
    Jan Bennett
    FS: VW MKIV Bezel for 8" Lilliput - 95% Finished

    Please post on the forums! Chances are, someone else has or will have the same questions as you!

    Comment


    • #3
      Alright then my next question is this: would I have to worry about overpowering the ECM (Computer Module) in my car? If yes, how hard is it to find a new chip to put in there and how much would I be looking at for price? Thanks again.
      CarPC: 100%
      Software: 100%
      Amps/Subs: 0% (on hold)
      Fabrication: Need help!!! Someone in Boston area who can help me with this please send me a PM.

      Comment


      • #4
        no - you wouldn't need to worry about that at all.

        just because you use a larger alternator doesn't mean the car is constantly seeing higher amperate.

        the only reason that would happen is if the voltage regulator were bad...and then you would have a number of other problems.

        Asking such specific questions about your particular vehicle and a chip for your EMC on a car pc forum isn't going to yield you many results.

        the people who post on here are average Joes. They do not know everything about every make and model of car out there, nor do they know about the aftermarket for every make and model out there.
        Jan Bennett
        FS: VW MKIV Bezel for 8" Lilliput - 95% Finished

        Please post on the forums! Chances are, someone else has or will have the same questions as you!

        Comment


        • #5
          Much thanks Red. I agree with you on you're last point, except for the fact that you've helped me out. When I'm all done with this stuff I'll let everyone know how it worked out. Thanks again.
          CarPC: 100%
          Software: 100%
          Amps/Subs: 0% (on hold)
          Fabrication: Need help!!! Someone in Boston area who can help me with this please send me a PM.

          Comment


          • #6
            dude, first, ditch the caps, overall caps do more harm than good, especially if your system is a daily, your alt spends extra effort trying to keep the caps charged, and this takes away from your batterie, and everything else.

            1500 watts: i would do the big 3 first with 1/0 wire, then prolly put a kc1400 in the rear, should be all you need, and im pretty sure your alt is 125.

            run 1/0 guage wire from your front batteries pos. and neg. terminals to the rear batteries pos. and neg. terminals, and you will be fine.
            1997 grand am GT BLACK ON BLACK!!
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            Kicker KX3 crossover
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            2.75 cubes tuned to 27 ish

            Comment


            • #7
              If I understand caps correctly, they are wired so that, if the voltage starts to drop across the amp, they kick in and supply the power that is needed. From what I've found on net, the stock WRX alt is around 75A. Therefore, There still is the questing of upgrading my alt, and if I upgrade my alt, there is no way in hell I'm going to put another battery in the back in addition to the alt upgrade. There is one other option: add a second alt. For the money tho, if anything makes sense, it's getting an alt upgrade, and that's what I think I'm going to do. Again, I'll let you people know. Peace.
              CarPC: 100%
              Software: 100%
              Amps/Subs: 0% (on hold)
              Fabrication: Need help!!! Someone in Boston area who can help me with this please send me a PM.

              Comment


              • #8
                Ok - the Cap discussion has been beat to absolute death on these forums. If you want to discuss it, use the search button and find the threads on it and discuss in there.

                If you upgrade your alternator, go ahead and get a better battery up front.

                Don't add a second alternator, there's just no purpose for it. It takes a good deal of work.

                Do the big 3 for starters anyways before you go any further. If you don't upgrade the big 3, the rest of it really won't matter much.
                Jan Bennett
                FS: VW MKIV Bezel for 8" Lilliput - 95% Finished

                Please post on the forums! Chances are, someone else has or will have the same questions as you!

                Comment


                • #9
                  Would I need to upgrade a deep cycle Die Hard batt? If yes then I'm looking at Optima Yellow top, right?
                  CarPC: 100%
                  Software: 100%
                  Amps/Subs: 0% (on hold)
                  Fabrication: Need help!!! Someone in Boston area who can help me with this please send me a PM.

                  Comment


                  • #10
                    upgrading the stock battery is always a good idea.

                    if you will run the car a lot with the engine off, then get a yellow top. if you won't be doing that, no need to spend the money. Go with a red top or something similar from other manufacturers. You want more reserve capacity than what your stock battery offers. If you can find out what that is, it would be ideal.
                    Jan Bennett
                    FS: VW MKIV Bezel for 8" Lilliput - 95% Finished

                    Please post on the forums! Chances are, someone else has or will have the same questions as you!

                    Comment

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