redman223

I upgraded the "BIG 3" already, and I have 2 amps and with the car on, one of them is running at 13.8 volts (the amp powering up my components) and the other one is at 11.8 volts (the sub amp).

I am going to buy a HO Alternator probably this friday, but the alternator will be a 150amp alternator, and I heard that 4 gauge wire only will handle 125 amps, (I used 4 gauge wire for the alternator to the battery) so will I need to change the wire?? If so, to what size?? I also have 4 gauge running from the battery to the distribution block and 4 gauge going to the amps.

One of the amps is 150x2 rms and the other is 500x1 rms, so only 800 total RMS watts, not a super system drainer. Will 2 gauge wire handle 150 amps??? and would I be able to run the 2 gauge from the alt. to the batt, and leave it at that?? Or will I have to run 2 gauge to the dist. block??? also???

rcurley55

Assuming that you have 800W RMS, with 50% efficiency, you are looking at a total maximum current draw of approximately 120A. So your 4 ga lead is just fine.

Keep in mind, the current carrying capability of a wire is dependent on two parameters, it's length and diameter. The 4 ga under the hood is only 6 feet long at best, so it will be just fine with the 150A.

vteg

You don't need to upgrade. At 150 amps output for 1 meter run you will get about .1 volt drop.

Oh yeah. I will give you my secret link. I use this a lot. http://www.stealth316.com/2-wire-resistance.htm

redman223

I kind of understand, but how do you figure in the 50% efficency? So basically I will be fine with 4gauge all around if I go with the 150amp alternator, and would I still just use a 125amp fuse (both from the alt to batt, and from batt to amps)?

Another question I had is how much of a difference voltage makes to the way the speakers sound in general? I am sure it is a no-brainer that 14.4 volts to the amps would be better than 11.8 but how much of a difference would it make? Would the sub bottom out less, volume be higher?

Thanks for your guys help.

rcurley55

Amplifiers are not 100% efficient. During the process, energy is lost as heat - that's why amps get hot while operating. So, if an amp puts out 100W RMS, but it's only 50% efficient, it needs to have enough input current to make 200W RMS - 50% is lost along the way as heat.

vteg

Upgrade your fuse to match the alternator output. Get a 150 in your case.

Voltage can make a big difference, or no difference depending on the amp. The higher end amps will give specs at 12.5(battery) and 13.8/14.4(running car).

As rcurley said, 50% efficiency is a good rule to follow without getting to deep into anything This is the general rule for AB amps. If you have a class D, you can probably use 75% efficiency as a guide.

My Arc 1500DR claims 120 amp current draw at 1000 watts output. That means it is only 60% efficient It is a class T amp.

rcurley55

one thing to keep in mind....if that fuse between the alternator and the battery goes....your car will die....

redman223

oh ok, so ill definently have to replace all my fuses, i still have the stock GSR teg alt. and its only 90 amps but my amplifiers fuses all add up to 100 (is that important?) so i tried to match that, right now I have a 70amp fuse from the alt to the batt, and an 80 amp fuse from the batt to the amps.

Do they make a 2 fuse box type thing?? So that I can have 2 ANL 150 fuses in it? (so both alt to batt and batt to dist. block wires can be fused) or will I have to have 2 seperate one fuse holders, I just think it would look cleaner with the one block with 2 fuses in it.

vteg

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by rcurley55 &raquo;</TD></TR><TR><TD CLASS="quote">one thing to keep in mind....if that fuse between the alternator and the battery goes....your car will die....</TD></TR></TABLE>

True. Make sure your fuse is at least as big as your alt's output.

vteg

Upgrade the fuse from the alt to the battery. The other fuses will vary depending upon what is connected to them. If it is working for you now, leave those fuses the same.

vteg

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by vteg &raquo;</TD></TR><TR><TD CLASS="quote">

True. Make sure your fuse is at least as big as your alt's output.</TD></TR></TABLE>

Ooops I forgot. Rcurley, when I do the upgrade I keep the stock wire in place also. So if the fuse blows, I will not stop rolling. I might get a lot of dimming though. I think this is the only way you should set it up. I know some cars do strange things if you completely bypass the stock connection to the alt.

redman223

Well i just checked it all out again, and now when the car is on the small amp was at 14.4-5 and the big amp was at 13.1-2 but with the car off the small was 12.5 and the big was 11.8, but I wasnt playing it too loud either and the lights were off (they were last time too though)

weird

Ok, so when I get my alternator I will need to change out the 70amp fuse for a 150 amp fuse, from the alt. to the batt. but you said that i need a different one from the batt. to the amps??? Could I get away with using the 80 amp fuse thats on there now, or should I just buy another anl 150 amp fuse?

vteg

I meant that the fuse from batt to amps is fine.

Also, the 13.1 voltage reading. Was that at full volume?

redman223

No, it was at a pretty low volume, so I'm gonna give the HO alternator a try this weekend, hopefully it will arive and be installed by next weekend.

vteg

Check your ground for the sub amp. At low volume I get 14.2 at the sub amp. I get 14.4 at the batt.

redman223

Hopefully it is not that, because unfortunately, I accidentally covered up every spot in the car with B-Quiet brownbead.......even the old ground holes, so I ended up using bolts where the seat belts are at under the back seat.

But I'll take a look