Is there some kind of basic guideline for watts to amperage?

[Gatorade]

Is there some kind of basic formula that dictates the amount of amperage needed to support the level of wattage being used? Say if you have xxx amount of watts you need xxx amount of amperage support. There's got to be a basic guideline, right? For example I'm running 2.5k rms what size ho alt do i need to shop for?

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[LoudSound]

amperes*voltage=max wattage

2500watts/14.4v=173.6A

but yea, what the man below me said.

you can run a lot more than 2500watts on 173A

 

[Jeffdachef 5,000+ posts]

You are better off installing a voltmeter and all your stuff and see where your voltages drop. Sh*t on paper almost never translate to real world performance, there's waaay too many other unknown factors that you cannot properly put into your equation. Such as actual alternator idle, vehicle power draw, box rise(which dictate ACTUAL current draw, you arent drawing 250 amps at all times, especially on music, meaning your amp will never produce a constant 2500 watts, if you wire to 1 ohm, best it can do is 500-1200 watts after rise on average not because its a bad amp or anything, its just how all amps work aka physics.), amp efficiency, battery reserve etc...

I ran 2400 watts a stock 80 amp corolla alt, with plenty of battery power, no drops under 13. While some other cars basically die out with just 600 watts.

 

[LoudSound]

Say word 2400 with a corolla alt. I have a corolla with a corolla alt. Good to know it can handle that much.//content.invisioncic.com/y282845/emoticons/fro.gif.c695f1f814b01c4ad99fe7f8cccadd29.gif

 

[Jeffdachef 5,000+ posts]

Say word 2400 with a corolla alt. I have a corolla with a corolla alt. Good to know it can handle that much.//content.invisioncic.com/y282845/emoticons/fro.gif.c695f1f814b01c4ad99fe7f8cccadd29.gif

had like 3 kenetik hc 1800s though, every month needed a trickle charge overnight to top it off.

 

[Gatorade]

Lol.. I was told that every 100 watts needs 10 ampere of support. So if you ran a 1000 watt amp you would need a 100 amp alt. That's just for audio. So figured with a 300 amp alt i could get 2500 rms of audio, and have plenty left over for the car. Omg, those d*mn self proclaimed audio gurus i work with.

 

[Jeffdachef 5,000+ posts]

Lol.. I was told that every 100 watts needs 10 ampere of support. So if you ran a 1000 watt amp you would need a 100 amp alt. That's just for audio. So figured with a 300 amp alt i could get 2500 rms of audio, and have plenty left over for the car. Omg, those d*mn self proclaimed audio gurus i work with.

Thats the information you read on paper but when you go into a real world perspective, there's wayy too many other viarables they never even accounted for. Music is dynamic, you arent playing a 50hz sine wave at all times, there's peaks and dips and different levels of bass in the recording and they all affect your amplifier power output.

with a true 300 amp alt and some battery reserve, you can run an 8k wired at 1 ohm no problem. 8k at half ohm or lower would be a different story but you can either supplement with more alt or more batt power. More alts would mean you can keep 14 volts and up easier, more batt would mean you would settle for 12.6-12.8 volts. Two paths to do it, both will work and get you loud, the alt path can help you squeeze out a tiny bit more watts out of your amp if you can keep it 14 volts and up. However sometimes people cant fit more than 1 alt or that big of an alt thats why there's a battery reserve path.

Generally with electrical, i'd have all the gear in first, monitor your voltage and slowly go up with the volume knob to see how your car handle's the voltage drop then make additional electrical upgrades accordingly.

Buddy of mines has a jeep patriot stock alt on an FSD 2600(does rated power on the dyno) at 1 ohm with only the big 3 upgrade and agm under the hood and he manages a solid 13.2 volt drop at the lowest. Box rise is a real thing, you'll never see as much power as you think you see. Literally whatever amp you have, look at 2-4 ohm power ratings, thats what you'll actually see if you clamp it wired to 1 ohm. Couple that with music being dynamic, your actual power output while playing music is rather low. One of the big reasons why you see people throw 1500 watts to a 750 rms subwoofer with zero issues.

 

[winkychevelle 10+ year member]

My general rule of thumb is to have at least 75% of max amp draw available from the alt and at least 50% of max available from the battery reserve a/h rating.

So if you have an amp with a 200amp fuse i would look for at least a 150amp alternator and at least 100a/h of battery reserve. This being in addition to the factory requirements. Can't fit a big enough alt add more batts.

 

[hispls 5,000+ posts]

Lol.. I was told that every 100 watts needs 10 ampere of support. So if you ran a 1000 watt amp you would need a 100 amp alt. That's just for audio. So figured with a 300 amp alt i could get 2500 rms of audio, and have plenty left over for the car. Omg, those d*mn self proclaimed audio gurus i work with.

First of all, you can't use Ohm's law to figure out max current draw of your amp because it's only going to be operating at 80% efficiency. On the bright side, unless you drive around listening to a test tone at just shy of clipping you'll draw relatively little current over time anyway. I'd suggest a high output alternator and a 55AH additional battery or a couple 55ah extra batteries and see how you get by on the stock alternator for 2500W. Start from there and add as needed.