What is the biggest system I can have on stock electrical?

[-unknown-]

The formula that crutchfield and sonic electronix recommends for determining the correct power / ground gauge is watts x 2 / 13.8. I don't 100% understand this but I get the concept. How do you know what the biggest amplifiers are you can use on an alternator like mine which is 128 amp If I remember correctly? Rockford fosgate lists recommended alternator amperage in their specifications. A R500X1D amp is recommended to be on at least a 75 amp alternator in their specifications. If you had 2 of those do you just add 75+75 and say I need a 150 amp alternator at least? I hope I'm explaining my questions clearly enough for somebody to clarify / correct me.

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[DaytonLax14 10+ year member]

You don't know until you try to be honest...how many watts are you trying to push?

 

[-unknown-]

Right now I have a Rockford Fosgate R500X1D and an Alpine MRV-F300, total 700 watts rms the way it's wired. I think the birth sheet on the Rockford says 645 watts rms though, so would that make it 645 + 200 rms? The alpine is wired so that all 4 speakers are supposed to be getting 50 watts rms. I'm really trying to just get an idea of what I want to do, in the probably not so near future. Who knows?

 

[mylows10 5,000+ posts]

What car ?

 

[-unknown-]

1999 Jeep Cherokee XJ

 

[mylows10 5,000+ posts]

Most cars and trucks. Can do up to 2000 rms on a stock electrical. With a Agm battery or two, a big 3 kit and 0 gauge wiring

 

[DaytonLax14 10+ year member]

With only 700 watts I'd guess you'd be fine on stock electrical

 

[-unknown-]

I know, I've had my system installed for a about a year, more or less. I'm just trying to find out a better method of knowing what you can or can't have, on certain amperage alternators.

 

[mylows10 5,000+ posts]

Generally most cars 2000 or less

 

[-unknown-]

rms x 2 / 13.8 = gauge power / ground in case of a malfunction, drop in voltage, or your fuse doesn't blow your wire won't be damaged.

so maybe rms / 13.8 = x and if x is well below your alternator amperage your ok? Idk.

When I setup my current system I figured I was ok because the the number I got to determine the gauge / power because was still under my alternator amperage.

The only other thing I know to do is find if it says recommended alternator, like on Rockford Fosgate amplifiers and add those up.

 

[n2audio 5,000+ posts]

There are so many variables involved it's really difficult to come up with even a rough guideline.

Replacement alts I'm seeing for a 99 Cherokee are 117A.

ANY aftermarket electronics add load to the alternator. At what point that load becomes a problem is where the gray area lies (and there's a LOT of it).

Most of us that have followed the hobby for a few years have read problems people are having with 500w rms while others blast 1500w rms constantly with little to no trouble which is clear evidence of the difficulty in saying what's too much and what is ok.

Plus, what is actually a "problem" may not be known until damage is done. My previous car, for example - had a 130A alternator. I ran 1500w rms in it. Day-to-day it ran perfectly fine, but two of those alternators failed in 3 yrs. So WAS there a problem? Well, no, it ran fine day after day, but YES, the alt failed every 18 mo.

IMPO - at 1000w you should assume the alternator is working pretty hard. If you blast it a lot, especially at low engine speed count on the life of the alternator being significantly shortened. Whether that's 10 yrs to 8 yrs or 5 yrs to 1 yr is impossible to say.

Going up from 1000w will clearly make things worse.

You can effect the situation a lot simply by keeping the volume down. A 1000w system at full volume will draw 30-40A almost continuously. At 1/2 volume you're looking at 10-15A.

My approach has always been to install what I want to install, and know how to replace my alternator.

I made sure the replacement part I bought had a lifetime warranty so my blown alt only cost me the time and hassle to replace it -- well, it cost me a tow too, but fortunately my insurance company reimbursed me.

The other option is to put in a big HO and hope it lives up to its specs.