trying to get 4 gauge power wire from alternator to battery

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trying to get 4 gauge power wire from alternator to battery

March 08, 2013, 02:21:39 PM

anyone have any pictures of a power wiring upgrade from a stock alternator?

trying to get 4 gauge power wire from alternator to battery

Reply #1 – March 08, 2013, 11:19:41 PM

PA Performance. $55 shipped for the "basic, ~$75 for the deluxe. I have one of each: Deluxe on the T-Bird, basic on the Mustang. Very nice set up.

trying to get 4 gauge power wire from alternator to battery

Reply #2 – March 09, 2013, 07:38:33 AM

I ran 4gauge around the firewall to a 150amp fuse to the battery side of the solenoid.

trying to get 4 gauge power wire from alternator to battery

Reply #3 – March 09, 2013, 01:34:39 PM

Quote from: 86T-bird;410811

PA Performance. $55 shipped for the "basic, ~$75 for the deluxe. I have one of each: Deluxe on the T-Bird, basic on the Mustang. Very nice set up.

I wasn't very fond of the PA Performance one when I looked at it. I'll have to look again (still on shelf) as to why. It had something to do with the connections at the end of each wire length. Soldered ring terminals on both ends is the only reliable/removable way to make cables. They are good if you don't want perfection though.

I will be making my own soon, after I swap parts on the top end and accessories. My current 1/0 gauge is too bulky, having broken off one alternator stud years ago, and not being easily routable on the radiator support (I ran it across the accessories). It's rare to go over 50A, even with a larger stereo, so why worry about losing 2% of the power?

trying to get 4 gauge power wire from alternator to battery

Reply #4 – March 09, 2013, 04:10:05 PM

Please enlighten me why in the world would you need a #4 cable from the alternator. just asking as it seems a little OVER THE TOP!!!

trying to get 4 gauge power wire from alternator to battery

Reply #5 – March 09, 2013, 05:52:31 PM

Quote from: TOM Renzo;410840

Please enlighten me why in the world would you need a #4 cable from the alternator. just asking as it seems a little OVER THE TOP!!!

Over what? Stock wiring into the cabin is . The biggest benefit of a new straight 4awg run over a straight 8awg run would be up to 30% more output from the headlights if they are also relayed. It will also prevent the alternator from maxing out at idle when you are stopped (4-6 tail lights on) and having all of the system plummet to under the battery's voltage, making everything dim to half as bright. Why just burn up power as heat in the wiring, rather than make it used by the drain?

With the length of the factory alt to battery cable with alt on passenger side and battery on drivers, the losses for just that section of wiring may be:
At 40A alternator output:
8 awg: 2A lost as heat, 0.6V drop
4 awg: 1A lost as heat, 0.2V drop
1/0 awg: 0.5A lost as heat, 0.1V drop

At 80A alternator output:
8 awg: 10A lost as heat, 1.2V drop
4 awg: 3.2A lost as heat, 0.5V drop
1/0 awg: 1A lost as heat, 0.2V drop

At 130A alternator output:
8 awg: 22A lost as heat, 2.0V drop
4 awg: 9A lost as heat, 0.8V drop
1/0 awg: 3A lost as heat, 0.3V drop

The voltage sense wire that goes back to the alternator will help it compensate, but the alternator will max out sooner. Not on our cars, but on those that can cruise on the highway at under 4kW of energy (5-ish HP), the reduced losses can improve economy by up to 5%, but I'd take a more conservative assumption that this would be closer to nill, but then again, there is definitely too much load with my lights turned up. The car can't stay in lean burn (75mpg+) at more than 55mph, while it can do it easily at 65-70mph with the lights off. Summer bumps that up to 80-85mpg, so there are of course other variables.

Then there's just those people who are in sound competitions and need every available Watt of energy, or those that are OCD about voltage losses. I think 4 gauge is perfect for a normal vehicle from the alternator to battery. I used 1/0 years back because I was into the whole sound system thing, and wanting every last volt to the trunk, but it never went anywhere except me trying to bump up efficiency in the car. I've gotten to the point where I'd rather have the ease of use (also the reason for me getting away from gt40p heads) instead of going to the extremes such as the 1/0 wire.

Either way, there are a lot of other variables, but 4awg is the minimum that I ever recommend to people. 4awg isn't physically big, it's cheap, and it cuts down on wiring resistance/burned off power. Now if only people also made proper connections...

trying to get 4 gauge power wire from alternator to battery

Reply #6 – March 09, 2013, 06:47:36 PM

I am totally in denial of your post. As i work on over the road trucks with 4 1200 CCA battery's in parallel and 200A alternators and they do not have any charging issues with #6 alt wiring. The pre-heaters draw 120A and the recovery time on the battery's is like 10 minutes at 60A MAX. The rigs have a load twice of any car on the road. I do know that heavy wire is OK but it comes to a point when it gets ridiculous.

So with a 120 A alternator if i read the voltage at the battery that is 50% discharged. i will see a charge rate at 12.7 V and a 22 AMP loss of current with stock wiring??? NOT HAPPENING!!

trying to get 4 gauge power wire from alternator to battery

Reply #7 – March 09, 2013, 09:17:48 PM

Quote from: TOM Renzo;410857

I am totally in denial of your post. !

http://en.wikipedia.org/wiki/Ohm's_law

My figures above were assuming 10-12ft wire lengths between the alternator and battery. Battery to fender/frame, fender to radiator support (or firewall), across to passenger side, back toward alternator along fender/frame, down under airbox, and backup to alternator.

I think 4awg is fine for up to 200A in scenarios where every watt isn't needed. I'd jump over 2awg and go straight for 1/0 or larger for any higher amperage.

Quote from: TOM Renzo;410857

So with a 120 A alternator if i read the voltage at the battery that is 50% discharged. i will see a charge rate at 12.7 V and a 22 AMP loss of current with stock wiring??? NOT HAPPENING!!

This is one of the other variables. I know my 130A alternator's good up to 165A. If you are putting out 120A on a 120A alternator (which let's say will actually do 140A max when new), the alternator can sense the lower voltage due to losses and output more (let's say 140A) to help maintain 14V in the sensing terminal. Alternators that either keep the sensing internal, or if you jumper the output back into the sense terminal immediately, cannot compensate for the losses in the system and you will experience the lower voltages at the battery. The sense terminal is one of the many variables that come into play with the electrical system. It still comes down to the alternator needing to output more power to make up for the losses in the wiring (or other areas). This is also why the 4 wire alts are a bad idea - they do not compensate for high resistances in the wiring, which could eventually lead to dead batteries, even with a good alternator. That is just theory though - I'm not sure anyone's wiring or connections have gotten that bad before it'd just catch on fire. At that point, there's far more serious issues.

trying to get 4 gauge power wire from alternator to battery

Reply #8 – March 09, 2013, 11:21:58 PM

Here is a wake up call SEEK no alternator can put out there max amperage rating. They would burn up pr0nto. Anyone versed in the charging system would know that. Read the instructions on a new alternator and it spells that out QUITE CLEARLY. Not only that to get the full output of the rated capacity that alt has to be spinning at MAX RPM. If any alternator can exceed the AMPACITY of a #4 wire it has to be HUGE!!. I have rigs with 400A alternators with #4 wire and that is rare. What you do not understand is a battery can not be forced feed tuns of amps and not be damaged. For some reason people think the MAX OUTPUT is the determining factor of the wire size. IT IS NOT IN THE EQUATION. Your alt is a 130A unit i am thinking and it normally would never output anywhere near that amount. So i find it fascinating that people throw these numbers out as FACT.

This is one of the other variables. I know my 130A alternator's good up to 165A. Absolutely incorrect

Don't expect that replacing an existing/stock alternator with a high current alternator is a simple bolt on retrofit.

Almost certainly a true continuous duty high amp replacement alternator will be significantly larger than the alternator that it is replacing. If it's not larger, it's unlikely that it will be able to provide you, continuously, with the additional current that you are looking for.

The manufacturer knows that the alt will not be used continuously at it's max rating. They are hard pressed to be anywhere near 1/3 output at best. They desigh alternators to run app 1/3 there full rated output at best.

trying to get 4 gauge power wire from alternator to battery

Reply #9 – March 10, 2013, 01:55:22 AM

I think I will address some points one by one. I may be off base on some items, but I believe I understand the electrical system quite well. I have a bad habit of being an information der and not believing anything until I've actually seen it for myself in a controlled test environment, or heard it from numerous credible sources.

Quote from: TOM Renzo;410893

Here is a wake up call SEEK no alternator can put out there max amperage rating. They would burn up pr0nto. Anyone versed in the charging system would know that. Read the instructions on a new alternator and it spells that out QUITE CLEARLY.

The diodes, being solid state, are limited in its output due to heat and nothing else (as long as they are sized properly). The brushes "should" not be affected much, as they are used in an entirely different way than a generator. A quality alternator unit should have very little wear on anything but the brushes, but you also don't seem to get that with $200 units. My alternator is rated for 130A continous, 165A max (as are many "200A" units). Now I wouldn't want to run it at 130A all the time playing some sine wave through some subwoofers as that would put an additional 5hp (3.7kW) load on the motor. There are usage scenarios of alternators that are far more heavy duty than those seen on standard vehicle loads. The only niche area that I can think of for alternators is car stereo systems, where there are people who add a second alternator to keep up with their (pointless imo) sound systems. From what I have seen over the years, the OEM units fail but once you get up to about the $500 price point for passenger vehicle alternators, they can hold up without any issue. Perhaps they are sold as 200A units but can actually output 300A+. Yes these would be a bit larger physically.

Quote from: TOM Renzo;410893

Not only that to get the full output of the rated capacity that alt has to be spinning at MAX RPM.

My alternator is at max rpms by 2k engine. I'd have to find the numbers again, but the pulleys should put my alternator at "idle" 2k rpms when the engine is at the commanded 624 rpm idle. In pretty much all driving conditions, the alternator is at max rpms. When you're at an rpm that is too low for the load, you get voltage drop. The more power you lose in the wiring, the less the alternator can make available to the electrical drains within the vehicle. I don't think anyone likes their lights dimming when they comes to a stop, in the dark, with headlights, brake lights, and windshield wipers on. This situation typically draws up to 40A more from the alternator, versus everything being off on a clear summer's day. Add in an electric fan and may be at 60A + base electrical load. 70-80A continuous is a normal load for an alternator. Don't forget the losses as heat which may need the alternator to output 85-90A in the same vehicle operating conditions.

Quote from: TOM Renzo;410893

Not only that to get the full output of the rated capacity that alt has to be spinning at MAX RPM. If any alternator can exceed the AMPACITY of a #4 wire it has to be HUGE!!. I have rigs with 400A alternators with #4 wire and that is rare.

I do have a question - what do you consider "adequate" for wiring for each expected load? It depends on the duration that a wire will have to carry a load. For continuous current, the NEC provides some good guidelines for wiring size and the expected temperatures that the wire will reach (requiring a minimum insulation temperature so that it does not melt. 90C gets you 95A on 4awg wire: http://www.usawire-cable.com/pdfs/NEC%20AMPACITIES.pdf . By the time that your wire is getting that hot, you already have a ton of voltage drop and energy turning into heat within the wiring, rather than being utilized. Yes, if you're just cranking over a vehicle of driving down the road, you'll be seeing the 20-40A range instead. I refer to overbuilding for safety - I won't recommend anything that could possibly be unsafe, especially if one WERE to build a system that were to draw 80A+ average. I always build for the best final oucome, even when making electrical circuits - build for worst case and go from there. I expected that my horn upgrades may draw up to 30A so I built a cooling system for the MOSFETs that can handle 40A for 2 hours straight and remain under 80C. Will it ever reach this? No, but it can and everything is fused to the 10awg wiring used. The horns would fail long before the 10awg would heat up. Anyway, I digress...

Quote from: TOM Renzo;410893

What you do not understand is a battery can not be forced feed tuns of amps and not be damaged.

The battery only sees this current if it is discharged. The power will move to the drain, not the battery. The wiring to the battery is just a pathway, but it continues from there onto the rest of the chassis, and eventually reaches the drain. If there is no drain, the alternator provides the 14v for whatever to take, but the amperage will be next to nothing.

Quote from: TOM Renzo;410893

For some reason people think the MAX OUTPUT is the determining factor of the wire size. IT IS NOT IN THE EQUATION. Your alt is a 130A unit i am thinking and it normally would never output anywhere near that amount. So i find it fascinating that people throw these numbers out as FACT.

In a typical vehicle, wire size doesn't matter as much. I agree with you there. To minimize the losses in wiring resistance, bigger wiring is always better. People always want more headlamp output, and wiring improvements provide this. Yes, I have built my vehicle for all-around efficiency (as best one can with an old-tech v8) and now with the LED tail lights, expect to be saving another 10A at the bulb, 12A from the source, the alternator (since I am using the small factory wiring that drops from 14V to 11V with the stock bulbs due to inadequate wire size). I AM curious what I can get my alternators loads down to, but that's a completely unrelated topic.

Quote from: TOM Renzo;410893

This is one of the other variables. I know my 130A alternator's good up to 165A. Absolutely incorrect.

Would it be better if I called it a 165A alternator rated for 130A continuous?

Quote from: TOM Renzo;410893

Don't expect that replacing an existing/stock alternator with a high current alternator is a simple bolt on retrofit.

Almost certainly a true continuous duty high amp replacement alternator will be significantly larger than the alternator that it is replacing. If it's not larger, it's unlikely that it will be able to provide you, continuously, with the additional current that you are looking for.

In terms of these cars, the upgraded alternators have a bigger casing for the internal fan, and a bit more bulk for the additional amperage. A stock 130A alternator may only be able to handle 10-20A more continuous over the stock units, but it's there. In these cars, even the newer alternator designs bolt up, not that this really means much past a standard 3G unit. With some aftermarket brackets, there are even more choices available. I know people who do the car stereo thing think they need the 300-400A alternators, and they find ways to get them to work in their engine bay. I'm not sure why since the stock unit can get your music loud enough to cause hearing damage?

Quote from: TOM Renzo;410893

The manufacturer knows that the alt will not be used continuously at it's max rating. They are hard pressed to be anywhere near 1/3 output at best. They desigh alternators to run app 1/3 there full rated output at best.

I haven't tested an alternator myself at max load, so I'll take your word on that. I can only go off of what I hear, and know about motors and solid state electronics. There are many alternators that are factory or builder rated to sustain over 100A in a passenger vehicle. I'm not sure I want to be in a passenger vehicle that requires that kind of power generation capability.

My own personal maximum current limitations for wire gauges and the sizes I use for automotive circuits are below. For 100% duty cycle, I limit to half of these numbers.
18awg - 6A
14awg - 20A
12awg - 30A
10awg - 50A
4awg - 200A
1/0awg - 300A

As always, good to hear your side of things. I enjoy that you take time our of you day to explain your understanding of things to the best of your ability, as I also try to do. I think the biggest difference between our thinking is I come at it from an engineering quality standards standpoint (least loss, durability) where you are coming from a standpoint of "will it work and get the vehicle to do what I/it needs to do without problems?" . I'll stick with my recommendation for $1 per foot 4awg copper wiring. I also cannot recommend aluminum wiring due to it being a much poorer conductor and not solder friendly. My way of doing things may also be why I can spend $150 to get rid of an insignificant problem that no one cares about when I could have just spent $10. I just figure do it right the first time and never have a reason to come back and do something again. This ideology only works for some things though (apparently not drivetrain upgrades).

trying to get 4 gauge power wire from alternator to battery

Reply #10 – March 10, 2013, 03:15:58 AM

Here are some typical continuous loads that may be placed on an alternator:

20A   Electric Fan
12A   Tail Lights
3A   Marker Lights
7A   Headlights
5A   General Illumination of Interior
5A   Wipers
15A   Blower Motor
5A(?)   Engine

72A total. The wipers may be intermittent

10A   Electric Waterpump
5A   Stereo system

With an electric water pump, this jumps to 82A. Add a stereo system and you may need another 5-10A at "high volume levels". So we're looking at 90A continuous, yet alternators can last years with this load. People do this on daily drivers and standard 3G "130A" alternators.

trying to get 4 gauge power wire from alternator to battery

Reply #11 – March 10, 2013, 03:21:06 AM

Nice discussion gentlemen! I'll be back tomorrow with pictures of my 4awg wiring from Alt -> 125a fuse -> Solenoid -> Battery. If I remember correctly... And I did it for no better reason than it seemed like a good idea! Also the fear of having a fuse link burn my car down..

trying to get 4 gauge power wire from alternator to battery

Reply #12 – March 10, 2013, 09:26:17 AM

OK nothing wrong with more copper that is a given. But you do not have a 165A alternator in your car with a stock mount!! So below is a 200A alternator and look at how big they are. What you do not understand is simple an alternator does not put out continuously high current. If you ever bought a replacement alternator it comes with instructions. And it clearly says do not use this alternator on a dead battery. Always charge a dead battery first. This is simple as the alternator cannot put out it's max current rating continuously. So there fore a #4 wire is GOOD but a waste of time money and resources. Below is true 200a alternators. By the way your math is off on your wire size. Reason being you are calculating on continuous output which no alternator ever does. By the way Max alternator speeds are around 10,000 RPM. I have been messing with alternators all my life and i find it fascinating that people actuallt think they put out continuous amperage. THEY DO NOT!!

http://www.qualitypowerauto.com/catalog.php?item=159

trying to get 4 gauge power wire from alternator to battery

Reply #13 – March 10, 2013, 02:12:59 PM

Quote from: TOM Renzo;410921

OK nothing wrong with more copper that is a given. But you do not have a 165A alternator in your car with a stock mount!! So below is a 200A alternator and look at how big they are. What you do not understand is simple an alternator does not put out continuously high current. If you ever bought a replacement alternator it comes with instructions. And it clearly says do not use this alternator on a dead battery. Always charge a dead battery first. This is simple as the alternator cannot put out it's max current rating continuously. So there fore a #4 wire is GOOD but a waste of time money and resources. Below is true 200a alternators. By the way your math is off on your wire size. Reason being you are calculating on continuous output which no alternator ever does. By the way Max alternator speeds are around 10,000 RPM. I have been messing with alternators all my life and i find it fascinating that people actuallt think they put out continuous amperage. THEY DO NOT!!

http://www.qualitypowerauto.com/catalog.php?item=159

Those products are correct with my earlier claim that it takes a $500 alternator to be reliable at high, continuous currents. I'm not disagreeing with you there. If a manufacturer claims that they have an alternator that is xxx Amps max and xxx Amps continuous, I would assume we can use it at that continuous output without issue (not always true). Simply, the larger wiring will allow the alternator to "relax" and output less current, at ALL current levels, than if it were using smaller gauge wire. This means that either you will not surpass the level where it can output a continuous amperage, or you will not reach the levels where the output causes the amperage available to drop. If you're losing 10A in the wiring, that's 10A more that the alternator must output for no reason other than a couple dollars saved on the wiring. The numbers are simply based on the "laws" that everyone has been using to design and build electronics for over a century.

My 10A loss figures would be the above 80A electrical load, typical for my car in the dark. If I were using a 12ft 8awg wire, the alternator would need to output 82A to keep the battery from draining. If I were to use 4awg, this would drop to 75A generation being required. With my 4ft 1/0 gauge that I currently use, the alternator needs to output 72A continuous. My junk Napa rebuilds, which failed 4 times with their "lifetime warranty", many times failed to output this much current and the voltage would plummet to under 12.5V at a stoplight in the dark. Cruise speeds just wore it out. My 165A alternator? It handles the load without a problem. Luckily, with my LED modifications, saving 10A from the alternator will more than make up for me moving back to a 12ft length of 4awg wire that will burn away 3A of power.

My numbers are real in practice. I do excessive testing and could show that the Napa rebuilds cannot take a continuous 80A load for long - some last days or months but it was always the winter months that killed them. Quality alternators, which fit in the 3G housing, can provide over 100A without dying an early death. The cheapest I'd go with is a PA Performance alternator but there are also better units out there, for a much higher price. It's one of those things where you get what you pay for, but there are diminishing gains.

trying to get 4 gauge power wire from alternator to battery

Reply #14 – March 10, 2013, 02:48:49 PM

Tom you show neece nevilles, I work around them alot, they shouldn't be compared to something thats on a car. There humungous even for trucks,even there 90 amperes. I think the OP asked how to run a stock 2g alt. with 4gauge, not sure why he would want to do that. I took a pic of my 200A powermaster and it fits just like a 3g.You can't see the sticker on it cause it' facing the inside, It came off the v6 I took out.