Is my stock alt enough

[myowngod316 10+ year member]

what should i do to fix it? i dont know much about alts...

 

[iceteebone 5,000+ posts]

has anybody bought an alternator from mralternator.com? i was just wondering if they were any good or not.

 

[abfan1127]

here is the deal...

as long as the time average power consumption of the amplifier does not exceed the extra power ( ~40% of output ) of the alternator... nothing else matters, you are golden. The reason head lights dim when powerful bass hits is this: when the bass hits, LOTS of current is requested for the amplifier... almost like a short circuit. Well, this "short circuit" is much smaller than the internal resistance of the battery... all batteries have internal resistance, better batteries like Optima Yellow Tops have lower internal resistance, poorer batteries like those from Walmart have higher internal resistance... This internal resistance and the impedance of the amplifier create a "voltage divider", so the output of the battery drops... thus the headlights dim... the higher the current draw on the battery, the dimmer the lights, see? To correct this, apply a high discharge capacitor to the terminals of the amp... (1 Farad for every 1000 W, ie for 2000 watt system, get 2 Farads) Note: that if the amplifier pulls more power than the alternator can provide, no amount of additional batteries or capacitors will solve this issue...

Equations to know are Ohm's Law V = I * R

power W = V * I

efficiency = Pout / Pin

if you plan to have a system with over 500W of power

 

[n2audio 5,000+ posts]

I've been posting this a lot the past couple weeks, but I think it sums up high power audio quite well - especially lately when everyone running a 100 watt jensen is worried that their electrical system's going to fail.

Here's RC's explanation of powering a 4000 watt system.

Originally posted by Richard Clark: guys the math is really very siimple------4000 watts is 4000 watts and watts is always volts x amps-----so in a 12 volt system it would be 333 amps and at 15 volts it would be 266 amps--------now if we have to pass that wattage through a lossy system (like an amplifier) we have to account for efficiency losses and add a percentage----ie if the efficiency is 50% we have to double our starting amperage since the voltage is still the same------so a 50% lossy device outputing 4000 watts would draw 8000 watts-------at 13 volts this would be about 615 amps--------class AB amps range about 50-60% at full output and class D amps range about 60-80% at full output------NOW for the biggest factor-------if we are playing music we can automatically divide these numbers by 1/3 or more for short term values due to the crest factor of music and for long term values we can divide by even more-----there are pauses between songs and at the end of the disc where the current demands are VERY low and these affect the long term average quite a bit-----and---sooner or later you are bound to ride by a cop and might have to turn it down a bit-----its not likely that a long term value of more than 10% can be needed for actual power requirements in a real system-------so for that 4000 watt system most any stock alternator will do just fine since it is a rare system that requires more than 50 CONTINUOUS LONG TERM AMPS.............RC