Can stock F30 alternator handle 1800w of audio equipment?

squidlyboy · 07-23-2015, 12:33 AM

I currently am running a JL Audio XD800/8 (800 watts) amp for my main speakers and would like to add two 500w mono-amps for subs for the trunk, so the total wattage would be 1800w for the audio system. Doing some simple math on a 12v car system, that is 150 amps of draw. I looked up on RealOEM the stock F30 alternator, and it is rated for 170 amps. That only leaves 20 amps for the rest of the car - e.g. AC, headlights, ...

This would seem to indicate operating in kind of an iffy zone where the alternator would be working extra hard - i.e. lower life-span, burn out earlier, etc...

I know i'm not the only one who wants/has a set up like this. Anyone else have any issues with their lights dimming (or audio dimming), or any other battery/alternator issues when you are running this much equipment?

Btw.. i realize that in order to draw the full 150 amps off of 1800 watts of stereo equipment, the gain has to be set to 100% and the volume cranked 100%, but at the same time, i like to listen to my music pretty loud

obriennathaniel · 07-24-2015, 02:49 AM

1800 watts will only pull 125 amps, at max power, a little more if you want to calculate in the efficiency of the amplifiers. the car runs at 14.4V on avg, not 12v.

However you will wreak havoc on your cars electrical system if you tried to do that in the not so long run. BMW's are so sensitive that any huge voltage drops will cause sensors to read incorrectly etc, not to mention destroying your alternator in a matter of a few months if you do listen to your music that loud. I used to do custom car audio/alarms etc so this comes from experience.

Sussex_G20 · 07-24-2015, 06:20 AM

I defy anyone to listen continuously at those volume levels, if you do then it might as well be just plain noise for all the definition your ears would be able to distinguish after the irreversible damage caused.
Also even at high volumes with modern amplifiers the power draw is not likely to be continuous, given that, then it is more likely that the continuous power will be maybe 50 to 60% of the continuous rating even at higher volumes. Remember also the battery will act as a big capacitor or reservoir to damp out peak current demands.

Would be prudent to obtain a shunt and measure the current drawn by the equipment in operating modes. I suspect that you will find the continuous power drawn is a less than 'on paper' figures would suggest. Marketing men compile most of the data we see on products so there may be some 'tolerance' on the figures too.

If you do get draw in excess of 65% of the continuous rating then I would suggest you need to take other measures to ensure longevity of the cars electrical system. Do bear in mind of course that with AGM batteries the charge requirements are different from std batteries and therefore i would make sure you test you power consumption at 12v this will then give an additional margin when running at higher busbar voltages.

squidlyboy · 07-24-2015, 07:56 AM

Thanks guys - i appreciate the info

I guess when i say i like to listen loud, its minimally at 50% volume, and i kick it up to ~75% when a good kick-a** song comes on, or i get into 'spirited driving mode'

But between the info about 14.4v operating voltage, and really only being at 50% most of the time, i think that provides enough margin that i'm looking for!

Fronzdan · 07-24-2015, 11:35 AM

Advice for squid....don't ever get an e-car.

squidlyboy · 07-24-2015, 11:46 AM

Quote:

Originally Posted by Fronzdan

Advice for squid....don't ever get an e-car.

lol... wise guy

07-23-2015, 12:33 AM	#1
squidlyboy Major 577 Rep 1,035 Posts Drives: 2014 Alpine White 328i M-Sport Join Date: Jul 2014 Location: Chandler, Arizona iTrader: (0)	Can stock F30 alternator handle 1800w of audio equipment? I currently am running a JL Audio XD800/8 (800 watts) amp for my main speakers and would like to add two 500w mono-amps for subs for the trunk, so the total wattage would be 1800w for the audio system. Doing some simple math on a 12v car system, that is 150 amps of draw. I looked up on RealOEM the stock F30 alternator, and it is rated for 170 amps. That only leaves 20 amps for the rest of the car - e.g. AC, headlights, ... This would seem to indicate operating in kind of an iffy zone where the alternator would be working extra hard - i.e. lower life-span, burn out earlier, etc... I know i'm not the only one who wants/has a set up like this. Anyone else have any issues with their lights dimming (or audio dimming), or any other battery/alternator issues when you are running this much equipment? Btw.. i realize that in order to draw the full 150 amps off of 1800 watts of stereo equipment, the gain has to be set to 100% and the volume cranked 100%, but at the same time, i like to listen to my music pretty loud Last edited by squidlyboy; 07-23-2015 at 12:40 PM..
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07-24-2015, 02:49 AM	#2
obriennathaniel @obriennathaniel_f30 on Instagram 515 Rep 1,063 Posts Drives: 582whp/596wtq '13 335i Join Date: Jan 2014 Location: Houston,Tx ig:obriennathaniel_f30 iTrader: (0)	1800 watts will only pull 125 amps, at max power, a little more if you want to calculate in the efficiency of the amplifiers. the car runs at 14.4V on avg, not 12v. However you will wreak havoc on your cars electrical system if you tried to do that in the not so long run. BMW's are so sensitive that any huge voltage drops will cause sensors to read incorrectly etc, not to mention destroying your alternator in a matter of a few months if you do listen to your music that loud. I used to do custom car audio/alarms etc so this comes from experience. __________________ CG Precision VS-1 Exhaust\DR-1 DownPipe \| PS2 Turbo\Inlet \| PDU PI w/Fuel-it platinum kit & E sensor \| GFB DV+ Diverter Valve \| BM3 w/AIC2-V\|Tune CaryTheLabelGuy \| Full E85 \| ATM FMIC \| ER Chargepipe Inlet/Outlet \| AFE Intake \| BC Coilovers \| PSS 255/40-275/35 Velos Designwerks S3 two piece 19x9/19x10 \| Osram Xenarc \| LED retro \| AWRON digital AC gauge\|
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07-24-2015, 06:20 AM	#3
Sussex_G20 First Lieutenant 145 Rep 379 Posts Drives: G20 330i M Sport Join Date: Jun 2014 Location: South Coast - Eastbourne iTrader: (0)	I defy anyone to listen continuously at those volume levels, if you do then it might as well be just plain noise for all the definition your ears would be able to distinguish after the irreversible damage caused. Also even at high volumes with modern amplifiers the power draw is not likely to be continuous, given that, then it is more likely that the continuous power will be maybe 50 to 60% of the continuous rating even at higher volumes. Remember also the battery will act as a big capacitor or reservoir to damp out peak current demands. Would be prudent to obtain a shunt and measure the current drawn by the equipment in operating modes. I suspect that you will find the continuous power drawn is a less than 'on paper' figures would suggest. Marketing men compile most of the data we see on products so there may be some 'tolerance' on the figures too. If you do get draw in excess of 65% of the continuous rating then I would suggest you need to take other measures to ensure longevity of the cars electrical system. Do bear in mind of course that with AGM batteries the charge requirements are different from std batteries and therefore i would make sure you test you power consumption at 12v this will then give an additional margin when running at higher busbar voltages.
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07-24-2015, 07:56 AM	#4
squidlyboy Major 577 Rep 1,035 Posts Drives: 2014 Alpine White 328i M-Sport Join Date: Jul 2014 Location: Chandler, Arizona iTrader: (0)	Thanks guys - i appreciate the info I guess when i say i like to listen loud, its minimally at 50% volume, and i kick it up to ~75% when a good kick-a** song comes on, or i get into 'spirited driving mode' But between the info about 14.4v operating voltage, and really only being at 50% most of the time, i think that provides enough margin that i'm looking for!
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07-24-2015, 11:35 AM	#5
Fronzdan Lieutenant Colonel 309 Rep 1,750 Posts Drives: '24 M240 xDrive Join Date: Mar 2014 Location: MA iTrader: (0)	Advice for squid....don't ever get an e-car.
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