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How To Figure Total Current Draw & Wire Size

Discussion in 'Audio & Video' started by blacksandtaco, Jun 12, 2009.

  1. Jun 12, 2009 at 8:35 AM
    #1
    blacksandtaco

    blacksandtaco [OP] Well-Known Member

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    Can anyone tell me if this is an accurate way to measure total current
    draw for a car audio system?

    I got this from Crutchfield -
    Multiply the # of channels by RMS watts (450 Watts RMS x 2 Channels =
    900 Watts, 50 Watts RMS x 4 = 200 - A total of 900 + 200= 1100 Watts
    RMS)

    Double that amount to account for amplifier ineffeciencies (1100 x 2 =
    2,200 Watts)

    Divide that number by the average output voltage of running
    alternator, 13.8 volts (2,200/13.8 = 159.4)

    Divide that amp output by 3 to account for 1/3 signal requirement for
    average power in a test tone (159.4/3 = 53)

    So I end with a current draw of 53 amps. This seems kind of low for
    an 1100 Watt RMS setup. Can anyone confirm this?

    I'm planning on running 2ga power and ground wire and splitting off to
    4ga to each amp from my distribution block. My alternator has a 130
    amp rating and I have the heavy duty battery that comes stock on the TRD Sport w/ Towing Package. Will this set up require a stiffening cap or deep cycle battery and what are the differences/benefits between the two?

    I've received some feedback on this already but just want to confirm. Thanks in advance!
     
  2. Jun 12, 2009 at 9:10 AM
    #2
    Octane151

    Octane151 Well-Known Member

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    Are you trying to find what your speakers are drawing from your amp? I have a formula to find that number to tweek the gain on your amp if you need it.

    Also, I'm running a 0/2 gauge wire to a distro block, and splitting to 4 gauge to both amps. So far, I've had no charge issues and no dimming lights. I have the same battery/alternator setup as you with the tow TRD package. You should be good to go with that setup... no need for a cap on my system.
     
  3. Jun 12, 2009 at 3:38 PM
    #3
    blacksandtaco

    blacksandtaco [OP] Well-Known Member

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    Thanks for the reply. I'm trying to figure out what my total amp power draw is on the charging system of my truck based on the number of RMS watts each is able to produce. Have looked at other formulas and charts but have never heard of the 1/3 power requirement on test tones? Got the info from Crutchfield, which I always knew to be a reliable source. I figure close to 160a or 170a with most other formulas I've seen. But 53a just seems really low. What size amps are you running, RMS wise?
     
  4. Jun 12, 2009 at 4:59 PM
    #4
    Octane151

    Octane151 Well-Known Member

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    Ohhh! Sorry, I misread your question. I dabbled a little in electronics... That number does seem a little low. There seems to be a much easier formula and solution than what Crutchfield has put out. I found this basic formula for that, which is all you'll need in my opinion.

    P=EI ... Which is Power(Watts "P") equals volts (Electrons "E") times amps (current "I"). For example, take a 500 watt amplifier. When a vehicle is running, the charging system would run at 13.8 volts. So, your amp can draw around 36.23 amps. 500=13.8 x I
    500 / 13.8 = 36.23.

    So having two amps equaling 1100 Watts will give you 79.7 Amps. Hope this helps!

    BTW, I'm running two Alpine PDX amps... one is the 4.100 (4 channel 100 Watt RMS) and the other is a 1.600 (1 channel 600 Watt RMS)
     
  5. Jun 12, 2009 at 6:01 PM
    #5
    sooner07

    sooner07 1/2 man 1/2 amazing

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    Are you sure you don't mean amps? 80 volts will most likely kill every piece of stock electronics in the truck.
     
  6. Jun 12, 2009 at 10:06 PM
    #6
    Octane151

    Octane151 Well-Known Member

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    Good catch! I corrected it... guess it would help to proof read before a post, right? :p
     
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