Need Some Power Advice

[tubbedII]

I'm trying to prepare my blazer's power for the audio system I planning on getting, but I'm not sure what's really necessary. Right now it's just stock other than a chrome 1 wire 100 amp alt (I guess these really aren't that good?).

Here's my system:

• Kenwood Excelon 994 deck
• Polk Audio 6.5" components
• Polk Audio 6x9s
• 600 Watt 4 Channel amp for highs
• 2 12" Subs (not yet purchased)
• 1000 Watt Mono amp for subs (not yet purchased)

Other than the stereo, lights and a Jeep electric fan, I don't have any thing else requiring power that I can think of. I do have a single Viair compressor for my air tank, but it's only a back up.

So do I need to buy a better alternator, a better battery and should I do the "Big 3" wire upgrade?

[jimmydean]

My setup isn't that far off from yours. I have 2 amps and am planning to run a 140A 3 wire alternator with marine isolator and dual rear mounted batteries. I will also have 2 Viair compressors.

My 2 amps will draw about 45-50A (equal to about half the amps fused rating) that should be enough power for mine. Using a second battery as well as a capacitor, I should have no issues rocking the bock and still have a little juice to hit switches just in case I haven't pissed off ALL my neighbors.

Figure the current draw on the amp (a 30A fuse is roughly 15-20A draw unless hammered) then figure what the truck needs to run (most trucks do well on 60A) then add some headroom. So a single 600W amp would be 30A +60A for the truck, then maybe 15A for the compressor and a 100A alternator would do the trick.

Granted, these are all guesses and more power is best. But for most setups under 1000W shouldn't need more than a 140A QUALITY alternator.

[jimmydean]

Oops, I forgot your sub amp. the best way to figure your power needs are to take the rated power at RMS per channel, *2, then divide by the amount of power at normal operation of the alternator (13.8v).

So my amp for my mids are 60W/per x 4 = 240
Sub amp is 700W x1

(240+700)x2= 1880/13.8 136.23A

At normal operation, you should be about 1/3 capacity, so divide 136.23/3 = 45.41A

So again, my 2 amps will draw roughly 45-50A of current on a good day. Don't look at max power of the amp, look at the RMS rating for the load for the math.

[jimmydean]

I am running 2 10" subs of my 700W RMS.

[john_p]

so. if that was pure electronics you would need 35 amps. full volume.. but. do not look at the advertising. look at the power fuse.. are you running a 35 amp fuse? multiply the fuse times 13, that is max power draw.. plan for that,, i have seen 500 watt amps with a 10 amp fuse.. drawing 138 watts and giving "true rms of 500 watts".. that dream of perpetual motion can not do that well..

[tubbedII]

Thanks for the advice all... So I take it a good alt is in order. Do they make one that's a one wire?

I'm still looking for a sub/amp combo, but I'm shooting for the 1000 watt range since the top will be off most of the time. Any suggestions?
Posted via Mobile Device

[piecesparts]

Contact Tuff Stuff and get one of their 140 amp alternators. They carry about 80 amps at the engine's idle speed not the 35 amps most other alternators do. I have one on my 84 GMC and it handles my fans, 3 amps, and high power headlights without problems. I also had one on my 91 Silverado, but I have sold it. They have a good product and it lasts. Call them to get the right part number and then search the warehouses for the best price. I have ordered through Tuff Stuff before.

http://www.tuffstuffperformance.com/

[jimmydean]

Originally Posted by john_p

so. if that was pure electronics you would need 35 amps. full volume.. but. do not look at the advertising. look at the power fuse.. are you running a 35 amp fuse? multiply the fuse times 13, that is max power draw.. plan for that,, i have seen 500 watt amps with a 10 amp fuse.. drawing 138 watts and giving "true rms of 500 watts".. that dream of perpetual motion can not do that well..

WUT? Take the fuse rating and multiply by 13? You are saying an amp can pull 13x the amount of fused current without blowing? I think you have at least one typo in here, maybe a lot more.

You can use the fuses to get a "quick and dirty" idea by cutting the total fused rating in half.

Example: 2 amps, 1 = 30A fuse, 1 = 20A fuse. 30+20=50A fused current.

50A/2 amps = 25A ballpark current draw.

So you will want to provide at least 25A to this 2 amp setup.

[hairlesshobo]

I definitely agree with the capacitor idea. The biggest benefit of having a capacitor is that it will help protect your alternator from the sudden load spikes that occur when your subs hit hard. Its also a good idea to increase the size of your alternator to allow enough current to run the system and keep the battery charged. As for a second battery, this typically isn't strictly necessary unless you plan to use your system often while the truck isn't running. If you intend to go this route, I highly recommend that you isolate the two batteries. This will allow you to completely drain your secondary battery without risk of stranding yourself. If you go with a secondary battey, you will definitely need to make sure your alternator can charge both, run the electronics, and your system. Just my $.02.

[tubbedII]

Thanks again for all the advice all! I called Tuff Stuff and got part #7140ABULL which sells at Summit for $197.95...A little pricey, but then I've never bought a nice alternator in my life...so if anyone knows of a cheaper one that's just as good, let me know...or if that's a deal, just let me know to stop being so cheap..haha

I've been making decent progress on my blazer lately (no pics or anything cuz I'm just putting it back together), but I've ran into an issue with wiring all the things that require power and was wondering what everyone is doing for a junction type block off the battery.

I found this battery clamp in my drawer that I plan to put on:

You can't tell by this pic, but it has a big hole for the starter, a little smaller of a hole, and then 2 10 gauge holes for wires.

Here's my plan, let me know if I'm overloading the wires:

Biggest hole
-Starter Only

2nd Biggest Hole (can someone recommend a gauge size?)
-2 amps
-Viair compressor (only used as a back up)

1st 10 Gauge hole
-2 headlight relays
-1 Pressure switch for EDC

2nd 10 Gauge Hole
-Electric Fan relay
-Painless wiring fuse

[hairlesshobo]

The second largest connection is likely 4 gauge since that's a VERY common size cable to run for automotive audio purposes.

I personally think that should do the trick. I don't see a problem because you will typically be using your starter OR your other devices, I really doubt you're gonna have every electronic device on wide open while you are starting your truck.

One idea that I plan to do in the future is to setup a remote starter solenoid to help minimize head soak. A side benefit of doing this is that it will allow me to have a nice heavy distribution post right on the fender mount solenoid. Just another idea for you.

[tubbedII]

Thanks, hairlesshobo! I'm going to order some 4 gauge wire and a 3 fuse block for the amps and compressor. I can put off the alternator for now since I don't have the subs, but I'll make sure that my budget allows for the subs/amp/alt all at once.

[hairlesshobo]

Not a problem.

One more thing. As for the alternator, it may not be 100% necessary. I would definitely recommend it but you could get away without it. I am running a factory style 12si alternator and I have 2 amps, a 300w 4 channel amp and a 1200w stereo amp (running on a 4ohm bridge). The only complaint that I have is that at an idle (~450-500 rpm) with my headlights and AC blower on, the current drops a little lower than I would like. Other than that, it provides plenty for my setup. The only change that I wish is that I had an alternator capable of putting out more current at that low of an RPM.

[piecesparts]

Originally Posted by hairlesshobo

Not a problem.

One more thing. As for the alternator, it may not be 100% necessary. I would definitely recommend it but you could get away without it. I am running a factory style 12si alternator and I have 2 amps, a 300w 4 channel amp and a 1200w stereo amp (running on a 4ohm bridge). The only complaint that I have is that at an idle (~450-500 rpm) with my headlights and AC blower on, the current drops a little lower than I would like. Other than that, it provides plenty for my setup. The only change that I wish is that I had an alternator capable of putting out more current at that low of an RPM.

That is why you would want an alternator that carries 80 amps at idle. That is why I went with the Tuffstuff unit on my trucks. I am not sorry that I spent the extra bucks.

[hairlesshobo]

I completely agree, just haven't had the extra cash to spend yet.
Posted via Mobile Device

[tubbedII]

I re-wired all the power in the engine bay last night as described above! I put in line fuses on them all as well. I need a longer starter cable cuz it's maxed out and I just don't like the way it feels/looks, but Autozone's longest 1/0 wire was 38" which is what's on there now.