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View Full Version : Alternators and Stereo Upgrades?


Big Dogg
02-15-2009, 02:10 AM
I know this topic of stereo systems is usually beat to death but I was wondering if any of the stereo gurus could give some advice to determine if my alternator is big enough.

I have a 75 Amp alternator. I plan on re-amping my Tower speakers with a JL 300x2 pushing 150w RMS on each channel (2 channel), my cockpit speakers are on a Sony 4ch 600 watt amp (60w RMS x 4), I also have a sub amp, but I cant remember its exact specs but I know it is currently 2 channels bridged to 1 putting at 150RMS on that bridged channel.

Will I be drawing to many amps and hurt my alternator? I know there is an equation out there to figure this, however, I cant seem to find it.

Please feel free to give any advice or suggestions. Didnt want to have to change out the alternator and I dont think I will, but I just want to know that I will be safe.

scramison
02-15-2009, 11:11 PM
How many batteries are you running? I would suggest just running 2 batteries instead if your only running one. I have a dual battery setup and Im running 3 amps with similiar watts. No issues here on the stock alternator.

JimN
02-16-2009, 12:02 AM
I know this topic of stereo systems is usually beat to death but I was wondering if any of the stereo gurus could give some advice to determine if my alternator is big enough.

I have a 75 Amp alternator. I plan on re-amping my Tower speakers with a JL 300x2 pushing 150w RMS on each channel (2 channel), my cockpit speakers are on a Sony 4ch 600 watt amp (60w RMS x 4), I also have a sub amp, but I cant remember its exact specs but I know it is currently 2 channels bridged to 1 putting at 150RMS on that bridged channel.

Will I be drawing to many amps and hurt my alternator? I know there is an equation out there to figure this, however, I cant seem to find it.

Please feel free to give any advice or suggestions. Didnt want to have to change out the alternator and I dont think I will, but I just want to know that I will be safe.

P=IE, where P is Power (Watts), I is Current in Amperes (Amps) and E is Voltage. If your amplifiers put out 500W at 14.4V (the usual voltage assumed for full alternator output), it's drawing 34.7A if it could operate at 100% efficiency, which nothing can. Now add this to all of the other accessories that can be used at the same time. If you're more than about 50% over the rated output of the alternator, it might be best to run the stereo a little quieter unless you never go past about 50% on the volume control. Under normal use, if you touch a battery terminal and it gets hot, you need more.