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Car Audio Discussion
General Car Audio
is there a general guide line of how big an alternator needs to support howmanywatts
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<blockquote data-quote="akillj" data-source="post: 8309359" data-attributes="member: 644272"><p>You can do some math to ensure you have enough amperage. Let's say you have a 60 amp stock alt. Your car should use about 40-60% of this during running / normal conditions.</p><p></p><p>60 * .6 = 36a of power to run the car / maybe some accessories on. (We'll use the high estimate)</p><p></p><p>Let's say you're running a 5000w amp (RMS).</p><p></p><p>You can estimate how much current (amps) it's going to consume by dividing input voltage (14.4) by rated output power (5000w)</p><p></p><p>But first, since no amp is 100% efficient, we need to figure out how much power it's going to consume, to create that 5000w. Class D amps by design are very efficient. They're usually up to 90% efficient at high ohm loads. Let's assume you're running it at 1 ohm, which we can estimate would give you about 70% efficiency. This is not 100% accurate, just an estimate.</p><p></p><p>5000 / .7 = 7142w</p><p></p><p>It's going to consume 7142 watts to create that 5000 watts.</p><p></p><p>7142 / 14.4 = 496a.</p><p></p><p>496 + 36 = 532 (</p><p></p><p>You will need 532 amps of alt to sustain this amp constantly while running the car and a few accessories. This would apply if the amp was running a constant tone, like in competitions. But we all know music isn't just a sine wave. So with a few batteries to ensure the voltage is stable, you can get away with a lot less alternator.</p><p></p><p>Full equation: (AmpOutput / ExpectedAmpEfficiency) / AltOutputVoltage = Amount of Amps required to run that amp constantly. Add that answer to (StockAltAmperageRating * 0.4-0.6) = Amount the car draws when running + a few accessories.</p><p></p><p>Add the answers to both those and you get the maximum your entire vehicle could possibly draw at one time. (Not counting for other mids/highs amps, but it will usually be minimal)</p></blockquote><p></p>
[QUOTE="akillj, post: 8309359, member: 644272"] You can do some math to ensure you have enough amperage. Let's say you have a 60 amp stock alt. Your car should use about 40-60% of this during running / normal conditions. 60 * .6 = 36a of power to run the car / maybe some accessories on. (We'll use the high estimate) Let's say you're running a 5000w amp (RMS). You can estimate how much current (amps) it's going to consume by dividing input voltage (14.4) by rated output power (5000w) But first, since no amp is 100% efficient, we need to figure out how much power it's going to consume, to create that 5000w. Class D amps by design are very efficient. They're usually up to 90% efficient at high ohm loads. Let's assume you're running it at 1 ohm, which we can estimate would give you about 70% efficiency. This is not 100% accurate, just an estimate. 5000 / .7 = 7142w It's going to consume 7142 watts to create that 5000 watts. 7142 / 14.4 = 496a. 496 + 36 = 532 ( You will need 532 amps of alt to sustain this amp constantly while running the car and a few accessories. This would apply if the amp was running a constant tone, like in competitions. But we all know music isn't just a sine wave. So with a few batteries to ensure the voltage is stable, you can get away with a lot less alternator. Full equation: (AmpOutput / ExpectedAmpEfficiency) / AltOutputVoltage = Amount of Amps required to run that amp constantly. Add that answer to (StockAltAmperageRating * 0.4-0.6) = Amount the car draws when running + a few accessories. Add the answers to both those and you get the maximum your entire vehicle could possibly draw at one time. (Not counting for other mids/highs amps, but it will usually be minimal) [/QUOTE]
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is there a general guide line of how big an alternator needs to support howmanywatts
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