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  • #31
    Originally posted by jflorey2 View Post

    OK great that's a start. 7000 watts is 600 amps. That's doable, but it means multiple 4/0 conductors to a very large capacitor bank. At those currents, forget batteries; all of it has to come from a low impedance source. Impedance is the only thing that matters (wiring and source.)

    Next you are going to have to figure out average power. Your system does not take 7000 watts continuously. Get a scope with a current probe and measure the AVERAGE current you see. If it's less than 200 amps (and it most likely is) then you need only capacitance, not battery storage.


    Again, for your case, impedance is the ONLY thing that matters. It determines how much the 12V system will sag when the amplifier hits its peak draws. You are much, much better off with a 1 amp-hour ultracap with a series impedance of .01 ohms than a 1000 amp hour battery with a series impedance of 1 ohm. Do the math; the .01 ohm cap will allow the 12 volt bus (really 13.8 volts) sag to 7.8 volts; the 1 ohm impedance will allow the 12 volt bus to sag to almost zero.


    Or spend $140 on a BMOD0058; that's .02 ohms, which is a great deal for that impedance. Two in parallel gets you to .01 ohms. Or spend $500 on a BMOD0500; that's .002 ohms.
    Wire has already been taken care of. My system will not take out 7000 watts continuously especially while playing music. Average current will be about 300amps for me right now. And how long would the caps be able to hold that voltage up at a 500-600amp current compared to lithium cells I have?

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    • #32
      Originally posted by ahdiofreak View Post
      Wire has already been taken care of. My system will not take out 7000 watts continuously especially while playing music. Average current will be about 300amps for me right now.
      That's 3600 watts you are dissipating somewhere. Unless your car is heating up the whole parking lot significantly, you're not taking 300 amps average.

      Get a good current meter and a scope and measure what you are really taking. Then you will have a good starting point for a system design.

      Your batteries will give you 22 amp-hours. That means if you are really taking 300 amps (which you are not) they will run the amp for _maybe_ 2 minutes. (At those rates, your total capacity will be less than half the 1C capacity.)

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      • #33
        I found a facebook page that has DIYer for these cells specifically. People that are using them for car audio and more applications. I will bother them instead. Thank you guys for your time and input!

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