Electrical Alternator Advice

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Grimmjoww

CarAudio.com Veteran
Hey guys, I have a 180amp powermaster alternator, regular starting battery under the hood and a AGM 31 battery for the back. I have pure copper 2/0 welding lead running to the back and the big 3 are done with the same cable lol ( I had a spool where I weld). What am I good for power wise on an amp?
 
I'm running bass3k and a small 4 channel off a 320 amp alternator with a 50ah under the hood and 100ah in the rear with 1/0 ofc wire
 
Your "weakest point" in that is the alternator. Your stock alternator would have been good enough to run the vehicle. Fuel injection, ecu, headlights, brakelights, turns, AC, fans, all use something. If you have something made in the last 20 years you probably use 30- about 100 amps when everything is maxed, (and the new stuff with heated seats, devices plugged in, entertainment screens you are more than that). Your stock alternator will give you an idea of what they expected you to max out with a little cushion. Subtract that from your new alt, and it will give you an idea of how much you can throw at the amp without worry.

If it's 100 amp difference, then 100amps x 14.4volts = 1440 watts. You then plan for an amp being about 85% efficient so 1440 x .85 = 1224 watts is about the limit of what you want your amps to power.

Depending on what you have planned, your cable and battery will be good for 3 times that. If you could find what I would think would be about a 350 amp alt, (guessing, - 80 amps for your vehicle), then you're at about 270 amps (x14.4v = 3888watts x .85), and then you would be able to add about 3300 amplifier wattage (3304.8 watts) to your setup without worrying about it, or upgrading further.
 
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Your "weakest point" in that is the alternator. Your stock alternator would have been good enough to run the vehicle. Fuel injection, ecu, headlights, brakelights, turns, AC, fans, all use something. If you have something made in the last 20 years you probably use 30- about 100 amps when everything is maxed, (and the new stuff with heated seats, devices plugged in, entertainment screens you are more than that). Your stock alternator will give you an idea of what they expected you to max out with a little cushion. Subtract that from your new alt, and it will give you an idea of how much you can throw at the amp without worry.

If it's 100 amp difference, then 100amps x 14.4volts = 1440 watts. You then plan for an amp being about 85% efficient so 1440 x .85 = 1224 watts is about the limit of what you want your amps to power.

Depending on what you have planned, your cable and battery will be good for 3 times that. If you could find what I would think would be about a 350 amp alt, (guessing, - 80 amps for your vehicle), then you're at about 270 amps (x14.4v = 3888watts x .85), and then you would be able to add about 3300 amplifier wattage (3304.8 watts) to your setup without worrying about it, or upgrading further.
Its just a basic Jeep, only power options are windows lol.
 
Well hell, guess I will just do 1 sub that bangs around 1200rms or so lol. When I get a bigger alt I will step up.

I'd guess around 3.5-4k before your amp shuts down from low voltage and around 1-1.5k before you see noticeable headlight dimming.

Yeah so I'll clarify that for OP. The numbers I gave are for playing your stereo maxed out, for hours on end. If you listen to it like that with that wattage, you won't have any problems at all. There is still plenty of wiggle room in there.

If you listen to it for a few songs at high on full, once you turn it down, your alternator will be recharging your alternator at a rate greater than what you are using. Batteries are a storage bank, and with your second one, you probably have a good hour or two of playing a 1200w sub at full before it drains your battery with no alternator.

With that AGM battery, I'll bet yeah you're in that 3k-4K range (depending on the battery specs) where you wouldn't notice lights dimming until you start draining the voltage at a rate faster than what the alternator can recharge and for long enough to where it drops below 12v. With what you have and lets say 3K watts, it depends on the kind of music as to how much you are actually pulling, it's not constant. You would be recharging in between the bass hits, (it's not a steady, 100% draw). Rap is going to use more with all the bass. Rock, country, and just about anything else has less bass hit, and has a little more of a gap.

You can definitely go bigger than 1200W. Personally, I would feel comfortable with just under 1800-2Kw amp on that setup for rock music, and expect no problems. If you are driving at some time after you turn stereo down, and don't play it for more than an hour, you could go a little higher.

You can also turn down an amp, you don't need to set it for max now in case you know or think you might want a second or upgraded sub later.
 
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Yeah so I'll clarify that for OP. The numbers I gave are for playing your stereo maxed out, for hours on end. If you listen to it like that with that wattage, you won't have any problems at all. There is still plenty of wiggle room in there.

If you listen to it for a few songs at high on full, once you turn it down, your alternator will be recharging your alternator at a rate greater than what you are using. Batteries are a storage bank, and with your second one, you probably have a good hour or two of playing a 1200w sub at full before it drains your battery with no alternator.

With that AGM battery, I'll bet yeah you're in that 3k-4K range (depending on the battery specs) where you wouldn't notice lights dimming until you start draining the voltage at a rate faster than what the alternator can recharge and for long enough to where it drops below 12v. With what you have and lets say 3K watts, it depends on the kind of music as to how much you are actually pulling, it's not constant. You would be recharging in between the bass hits, (it's not a steady, 100% draw). Rap is going to use more with all the bass. Rock, country, and just about anything else has less bass hit, and has a little more of a gap.

You can definitely go bigger than 1200W. Personally, I would feel comfortable with just under 1800-2Kw amp on that setup for rock music, and expect no problems. If you are driving at some time after you turn stereo down, and don't play it for more than an hour, you could go a little higher.

You can also turn down an amp, you don't need to set it for max now in case you know or think you might want a second or upgraded sub later.
Right on thats good info. I have a solid 750cca 90ah cranking battery and this is my agm, its a very good battery, ran them on my bass boar trolling motor. https://shop.advanceautoparts.com/p...Y9aGSS7tY7Isoo_53KcaAmppEALw_wcB&gclsrc=aw.ds
 
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Grimmjoww

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