vorgath

I know one can get some from weldingsupply.com I can also get some 2 gauge from the electronics store here. The 2 gauge is the fine multistrand one.

But I also noticed Home Depot carries 1/0, 2/0, 3/0 etc, however it's a much stiffer wire, less strands, instead a dozen or so very thick strands.

Would it make any difference really ? As long as one gets real thick wires, like 2/0 or similar ?

It would be just more convenient for me to get it from Home Depot 3 miles from my house than ordering it online.


PS/ This is for the Big 3 and possibly relocating the battery to the trunk /DS

tom3

For full battery current load I'd run a minimum 1/0 wire. I used 2/0 on mine just to have some excess. The welding cable is good stuff, but a bit on the small side and it's some harder to keep in place since it's more flexible. The stiffer cable is not a problem, maybe a help for this use. I also tinned the wire ends before putting on ends to combat corrosion.

vorgath

This wire I'm talking about is extremely stiff.

So this kind of wire would be just as good as those from weldingsupply or Knukonceptz ?

Gummie

There are a bunch of factors at play here. High strand count wire is more ideal for car audio for three reasons. The primary reason is the skin effect. This is a very big deal and explains why higher strand count wires can move more current than lower strand count wires of the same gauge. If you don't know what the skin effect is click the link and learn about it. The second reason why you should buy high strand count wire is because of its flexibility, which will greatly ease installation in a car. Imagine trying to hide a strand of 2/0 (or bigger) that was designed to be used in a building – it would have an insane radius for any and all bends. The third reason is the availability of fuse holders and distribution blocks for gauges thicker than 1/0. Good luck finding anything for 2/0 for any kind of application. Fuse holders are a necessity and will save your car from a fire if anything ever goes wrong with your system.

0/1 can carry 330 amps worth of current. That's an insane amount of current. I've got no idea what you mean by a "full battery current load" but the wire will never carry more current than your amp(s) are capable of pulling, thus you should match your wire to your maximum current pull. If you're running a crazy system you're better off with multiple 1/0 strands than a single 2/0 gauge wire because of the complete lack of fuse and distribution blocks, not to mention the relative ease of installation. You must be running an insane system (3,000+ actual watts) to make use of that wire with only "some excess". If you don’t mind I would like to see some pictures of the setup including fusing, amps, etc.

As for keeping the wire in place, you should secure your wire every 3’ or so using something along these lines. If you’re going to be in any kind of competitions you will lose points if you haven’t done so every two feet. If the wire isn’t secured it’s free to bounce around and rub against things, which will eventually wear through the insulation and cause a short. If you’re not running a fuse this will mark the end of your car’s existence because of the fire that will result when your battery positive finds a new ground on the car’s frame.

I’m going to start over. Forget the first half of this post, here’s how you should buy a wire.

First, determine the maximum current your amp(s) is/are capable of pulling. You can do this by looking at their specifications or adding up the values of all their fuses. Second, think about whether or not you’re going to be upgrading your system at any point in the future. It’s always good to lay a good groundwork so that you won’t have to redo it in the future (ie start with 4 gauge and then upgrade to 1/0 in a year).

Once those two things have been decided consult this table:



Find a wire gauge that’s the next step beyond what your system is capable of pulling.

Running too small of a wire results in voltage drop, which means that your amps will be producing less power than they otherwise would if they were getting the full 13.8v/14.4v from your alternator. You also run the risk of a fire if your wire isn’t properly fused and has too much current flowing through it for too long of a time period.

To conclude: buy high strand count (Knukonceptz, Stinger, Elemental Designs, etc), fuse it, and don't go overboard if you don't need to.

For a nice write up on wire (along with calculators for voltage drop), check out this website

tom3

I guess I was somewhat confused by the original question. I was addressing the battery in the trunk deal. On a hot day with fans on, AC (heater) blower on, maybe headlights, and starting a hot engine you could see 2 - 300 amps for a short period. Take some serious wire to handle that with a longer run from the rear to the starter. The welding cable is good stuff, designed for high current, low voltage, rugged handling use. Audio equipment is a whole different animal with the sudden peaks combined with the continuous loading. Good reply by Gummie and the links have much needed info for sure.

vorgath

I was actually talking about both, Big 3 inside the engine compartment, but also about moving the battery to the trunk.

Gummie

My bad, completely missed the battery in the trunk thing but the same basic concept applies

NEEDAZ

Skin affect is not a concern here. This is DC. Skin affect is a function of a wires self inductance and only comes into play with AC, and in reality at high frequency AC, RF applications.

Fuse holders and distribution blocks are available. Look for ones that are designed to accept ring terminals and use ring terminals on the wire ends.

This is the only reason to get the high strand count in a car installs, and it's a BIG one. Getting the Home Depot wire to bend the way you'll end up needing it to to is a PITA, and forget tight bends. Welding wire is a good compromise.

Running 0/1 or 0/2 for a battery relocation is a good idea. You be surprised how how much resistance you can get in a power distribution system by the time you take the wire, and fuse holders, and ring terminals. At 300A it only takes 0.01 ohm to drop 3V.
For the BIG 3, 4 gage is usually more then adequate.
For amp installs, large gage wire can help with transients, if you care.

By the way, those charts can be misleading. You can pass 500A through 4 gage, just not for to long, a couple of seconds.

vorgath

So inside the engine compartment I should run 1/0 gauge or similiar, and if I run the battery from the trunk, use 1/0 or even bigger ?

Is there usually a loss in power or loss in recharge of the battery by relocating the battery to the trunk ?

NEEDAZ

Well, you have post how much current you'd be pulling, or what you're alt. can put out, but 4 gage is probably good for the under hood BIG 3. 0 gage or bigger for the battery is a good way to go, but you see people getting away with 2 gage.

You want to keep voltage drop to a minimum. You'll be OK with the battery in the trunk because as it charges, it will pull less current. As it pulls less current, any voltage drop will become less and less of a problem.

vorgath

So the way to do it is:

1) Battery in the trunk inside a sealed box

2) Box has to be vented to the outside (through a drain hole or something like that)

3) Run two 1/0 wires underneath the car, one for recharging the battery, one for supplying power to the engine etc

4) Both of those wires going up to a distribution block on the firewall or wherever in the engine compartment

5) Big 3 , 2 gauge or bigger

Anything I missed ?

HawkHunter

if you're relocating batteries, may i suggest gel batteries? I use them for my 24 volt hydrolic system in my trunk, they can be mounted in any position (they dont leak/spill) and for the few extra $ I think it's a great investment. Your local battery store or parts store should be able to get them for you. They're about 30-50 bucks more than a conventional lead acid battery depending on brand name and rating.

Cheers,
Trev

vorgath

Well problem is ... I'm more or less broke .. so, can't really do it, or I would run out and buy a really good battery

Gummie

Ouch, shot down twice in one thread

I will stand by the chart as a useful guide for audio installs. While you can pass 500 amps through 4 gauge without issues for a second or two it's not a good idea. It's not absolute but it is a good, safe, benchmark when it comes to installing components in a 12v enviornment.

NEEDAZ

Absolutely!

[R]ogue

hey all, I was given this in school it might help -
.
.
.
.

[R]ogue

a good starter motor on our 3rd gens shouldn't pull more than 150 amps, heck a good one normally pulls around 100 anyways as you can see its approximately 20 feet from the rear of the car to the starter on a 12v system a 4 gauge wire would be overkill, but hey its ya'lls dime so if ya wanna buy more expensive cable for no good reason then have at it

i like to cruise in my car with the gas money i save on cable so i can go down to the beach and check out all the hotties but thats just me

NEEDAZ

With 4 gage wire you drop 1.5 just over the wire at 200A. This doesn't include connection resistance at the ends were you'll lose more then that. Wouldn't be hard to end up less then 9V at the starter. With 0 gage you'd see about a half a volt drop over the wire. That's about a third of what you'd get with 4 gage.

I like a car that starts right up with no long cranks at the gas station.

camarojustin

When I did mine I used 0 gauge welding cable ( $25 from princess auto )from the battery in the trunk directly to the starter.I reused the cables from the starter to the distribution block (which was already there) and used 8 gauge from the distribution block back to the battery.
I have the old ground cable connected from the battery to the frame and another good ground from the engine to the frame.
The one thing I am missing is a fuse near the battery ( which I need to find and install

[R]ogue

where do you get these figures at?

sounds like you got a bad connection if you're dropping voltage at a connection.

the phone number for the school is right on the page I scanned I graduated in 92 so it may have changed, you can call them up and discuss it with them or.... for 14 years I've been repairing cars and trucks with the information I was taught and well.... for 14 years I've been quite successful..... so as you can see for a 200 amp load over a 20 ft span 4 gauge wire is sufficient according to the chart i provided and like i said the phone number is right there. if it matters any to ya the course material was approved by the SAE and well.... they have been an integral part of car manufacturing for longer than I've been alive.

camarojustin

Here's some stuff I learned in my electricity class.

Voltage = Current x Resistance
and
Resistance of 1/0 gauge is 0.328 milliOhms/ meter x 6m(18ft) =0.001968ohms

the resistance of 4gauge is 0.833 milliOhms/ meter...x 6m = 0.004998 ohms

so.. using 200 amps ( which is probably way more than it actually is )


V=IR.... Voltage = 200amps x 0.001968 Ohms = 0.3936 volts drop



V=IR.... voltage= 200amps x 0.004998 = 0.9996 volts drop


SO does 0.6volts really matter?(AT 100 amps those drops would be cut in half)

**If you tried that with... say.. a 14gauge wire you'd lose 10 volts though.


The insulation of the wire also plays a factor though

I hope this clears up some issues.

PS Rogue, I wish I could read that chart,is it blurry or am I going blind?

[R]ogue

nah its a little blurry I'll try another scan again when I get some time or see if i can edit it a little in photoshop or something

yea i hear ya'll on the voltage drop, i knew there was some but 1.5v that was said sounded kinda high to me - i was taught 0.2 volts max in school, in real life 14 years on the job i regularly measure up to 0.5 with no significant effects in the system as far as general repair goes - i was referring to what kind of wiring needs to be run to the starter if you relocate your battery to the trunk - basically rule of thumb I would go up one size ( down one number size ) from the stock battery cable or any wire you double in length

no i really don't see voltage drop as being a big problem with circuits working correctly - what matters is the amperage - as ya'll may already know the higher the voltage the more current you can flow through the same size wire.

i couldn't honestly tell you though in the audio world of subwoofers and stuff if the voltage drop would make an audible difference let alone a measureable difference

NEEDAZ

One, my post should have read 200A, I'll fix that. My numbers came from an on-line calculator that I've found usefully. I checked the reference folder at work and it just has a photo copied page so I can quote the source. It's different then what is posted. But this demonstrates why I hate those charts, it's easy to find them that don't agree. These charts should only be use as a ruff reference. Not all 4 gage is created equal.
I read these post before I went to work so rather then playing with the charts, I thought I'd get some REAL WORD NUMBERS.
I grabbed a DLRO when I got there and some random bits of big wire. The measurement where taken with a freshly calibrated Biddle 247001 @ 21.2*C. At that temp the 247001 is +/- 1/4% rdg + 1lsd. I also used the duplex clamp leads.

5' of 4 AWG Welding wire
1.346mohms or
0.269mOhms per foot

5' of 7 strand 2 AWG (this is what you would see at Home Depot and is often use in industrial) This particular brand (couldn't see the brand name) looked a little bigger then the other two 2 gage wires.
0.925mohms or
0.185mOhms per foot

1' 2 AWG welding wire
0.350mOhms per foot

1' 2 AWG welding wire(finer stands)
0.249mohms per foot

11' 2/0 AWG
0.782mOhms or
0.071 ohms per foot

3' 4/0 AWG w/ ends fitted that are crimped and soldered then covered(could not get to just the wire so these numbers also show connection resistance).
0.842mOhms or
0.280mOhms per foot, but NOT really, this also shows connection resistance, which would be higher in this cable. It's probably 10 years old and was in a diesel locomotive for the first 5.

And damb it, I couldn't find ONE piece of 0 AWG and the 0g spool is empty. So no numbers for that.

So going from the measured resistance for the 4g above over 20' you have 5.38mOhms (0.00538ohms x 200A = 1.076V). So you're losing 1 volt over JUST the wire. Now keep in mind how obvious the connection resistance in the 4/0 AWG above and 1.5V isn't hard.
And then wire temps will skew things the longer you're pulling current. Coppers resistance raises as temps increase. You wouldn't see to big a change here tho.

Next test at work. Put 200Adc into the 5' long 4 gage wire above. It starts getting noticeably worm after 5-6 seconds with 200A. Why? With 4 gage assuming you have a 4 gage wire with a radius of 0.101", that's radius of 2.588mm and a cross section of 21.044 mm2. So you have 41530 or so Circular Mils to work with in 4 gage wire. AT 200A THATS ONLY 207.65 Circular Mils per amp. You want at least 300 Circular Mils per Amp for continuous duty or 250 Circular Mils pulsed. (The 300 and 250 can be argued depending on how you talk to, but stand as a good rule of thumb.) I posted the measurements off a unknown chart at work as a reference, NOT ALL 4 GAGE IS THE SAME. It should be, but it's NOT. If you've ever bought an amp install kit form some off shore company, you may have seen this.

I'm using 200A because it wouldn't be impossible for an old starter on a high compression engine to pull 200A.

That's as real word as it gets.

You'll always have voltage drop at a connection. Most of the time not nearly enough to bother with, at 200A you need to start thinking about it.

It's an old car, things may not always work correctly. Do it with 0 gage and even when something fails, you're covered.

Sorry, but that's flat out wrong. Current is the only thing that matters when picking wire size. More specifically Circular Mils per Amp. With higher voltage you can deliver more power (in watts), NOT more current.

It can make a vary big difference. You only have 12V to work with, you don't what to loose anything you don't need to.

[R]ogue

NeedAZ -

again I was speaking in reference to the starter circuit which obviously isn't continous duty and i also agree to a slight degree when you said these charts should only be used for "ruff" reference

as far as the voltage drop in the connection - yea not usually enough to bother with except for in continous duty - again i'm referring to the starter circuit and most high torque mini starters on high compression and/or big cube engines normally pull about 170 amps - since you seem to be versed in electrical i'm sure you know that any motor, fuel injeictor etc etc when looked at with an oscilloscope will throw the same pattern a high peak draw then drop - matter of fact it looks a lot like a spark plug firing on an "engine analyser" ( which is an oscilloscope )

i know the chart i posted is hard to read and I'll try to fix that but again it meets SAE standards and well as far as the voltage amperage thing goes.... according to the chart 10 feet of AWG 6 is capable of 200 amps at 12 volts and 100 amps at 6 volts and well... even though I will agree not all wire is equal technically if it meets industry standards then at MINIMUM it is capable of doing what the chart says but since we don't like charts here lets go to our buddy Ohm's law -
with your example of 5' of #4 AWG measured at 1.346 ohms -
I = E / R with I= current, E = to voltage and R = to resistance then -
12 volts divided by 1.346 ohms = 8.91 amps
24 volts divided by 1.346 ohms = 17.83 amps
So.... as you can clearly see you MOST DEFINETLY can flow more amps at a higher voltage through the same wire

thats funny because the whole point of me saying you can flow more amps at a higher voltage was to basically agree with you on the fact that voltage drop is an important thing. i'm sorry if i offended you in some way. i stand behind everything I've said as far as starter circuits are concerned now stereo wiring on the other hand.... i would personally use the chart that I'll fix and up it one size for safe keeping. so basically if the chart says 4 gauge to do the job and you're wiring a heavy duty stereo then I"d use 2 gauge.

camarojustin

Those numbers you posted are pretty much exactly the same as the ones I did

vorgath

So 1/0 gauge is more than just fine for a battery in the trunk, two or three amplifiers next to the battery, plus several accessories (fog lights, LED lights, underhood lights etc whatever) up front ?

I have an Optima battery right now, and will try to find a 140 Amp CS144 soon.

NEEDAZ

vorgath, Yes, 0AWG back to the battery, 4AWG for the BIG 3. That is if you and up with all those accessories. And if you add all that under hood/lighting I would suggest you run to the junk yard and get a 'stud' style distribution block. Mount that to the fender and run 8AWG from the big starter wire to it, fuse appropriately. Just ends up making things easier.

This has turned out to be a nice little thread.

Yes yes, starter circuit should be intermittent. But I don't know vorgath, and I hope he wouldn't be the guy cranking on the starter for 10 15 seconds trying to figure out if he flooded it or if the coil when south. One of the Bull Dog remote starers had a miss-print in the install manual that had people killing there starters because it kept the starter engaged the whole to it was in remote start mode. I work as an electronics Tech with a good background in mobile electronics, I've seen odd crap happen and people do stupid things. I'm taking that heavy into consideration when recommending something. It also makes me a believer in glorious excess.

[R]ogue, I think your really close to having a much better understanding of electricity and power destitution. You just a little off in the application of some theory. We'll straighten it out. But thats going to be a long post, and it's 2:00am, I've only got 4 hours of sleep the past three nights, 2 jobs suck, and I electrocuted myself at the night gob again to night. It sucks when the insulation is bad in the insulation test sets. Time to sleep now.......

NEEDAZ

No No, not at all. I'm sorry I didn't say that in the post above, it was late. Hope I'm not offending you. I like the back and forth. I think it's the posts like this where the newer people will learn the most. There's a lot of great detail in here. Every one is backing up there assertions with some good info and I don't think it's gotten personal like these post can go sometimes.

When considering voltage drop at a connection it's more about how much current is there, not how long it's there. The resistance at a connection will more or less stay the same, So if Resistance stays the same, and Current is going up, Voltage drop will also go up. Current goes down, so will the voltage drop. Now the longer and more power you are loosing, the hotter it will get, and that can get bad too.
P=EI (P = Power in Watts)
Power is how much work is getting done, or can be done. Power lost to inefficiency is lost as heat. Heat is bad.

Yes, In-Rush current, and can it be many many times the normal current consumption of a given device/load. But it's most often vary quick so there isn't enough time if the wire to over heat/melt. But again if the wire is to small, even the fast in-rush current can over heat the wire.

That was 1.346m ohms. That's 0.001346 ohms. Or 0.0002692 ohms per foot.

We're missing what they're basing that off of, should be a certain percentage of lose. Look at the 5' 4AWG at 1.346m ohms. At 200A you'd have a 0.2692V across the wire. That's 2.2% of the supply voltage (12V) or 4.4% of supply voltage if you cut supply voltage in half (6V) and current staying at 200A. Cut the supply Voltage in half and the ratio of supply voltage to voltage drop doubles. To keep the voltage drop under a given percent you can only pass half the current. That doesn't mean that the wire can pass more current at a higher voltage. When the wire is forced to dissipate more power it gets hotter. To find how much power the wire is dissipating you multiply the voltage drop (not supply voltage) by the current.
Vd X I = Pw (where Pw is power lost by the wire because we are only
using the Voltage Drop(Vd) of the wire).
0.2692 X 200 = 53.84W (needs to be dissipated by the wire)
0.1346 X 100 = 13.46W (this one is 0.1346 instead of 0.2692 because
with half the current flow you'd see half the Voltage Drop across the same resistance)
You can see that with 1/2 the current, you have ¼ the power, because
the load resistance didn't change.

The problem here is you used the supply voltage, not the voltage drop
on the wire. What you have said here mathematically is that if the had a
battery (12V) and put a 1.364 ohm load across it you have a circuit
with 8.91A of current flow. Which is right. But if you are looking at one
part of a circuit, you would use the voltage drop in that that part.
Using the supply voltage with 0.001346 ohms (5' 4AWG) you'd be trying
to pull a theoretical 8915.3A! Really you never get because of
limitations in the battery.


Is any of this making sence?

vorgath

Stud style distribtuon block ??? Which cars had that ?

I got myself a CS144 alternator (the 140 Amp version), still trying to 1) Find a brush set at a parts store, and 2) Figure out if the alternator will bolt right on or not, haven't been able to find that information on the forum, all I know is I'll need a longer serpentine belt.

[R]ogue

no not really making any sense to me... but I just got home from Biketoberfest and have been drinking for four days non-stop the onlyl thing I can say right now is that I wouldn't use Ohm's law to computer the amperage flow across a part of the circuit cause I would only be interested in the current flow of the whole circuit - and voltage drop in a circuit would be caused by a resistance in the circuit which would be in series with any other resistance which would increase the total resistance in the circuit which would lower the amount of current flowing in the circuit and a circuit won't flow any current until it is a complete circuit - hope that makes sense....

all I know is that my 220v air compressor has made a significant decrease in my power bill over my 120v air compressore and that be a kilo-watt meter outside there

NEEDAZ

vorgath, one like this Catalog
The wire can be found cheaper then this, but as a starting point. Catalog

Thinking about it now, you car should have one between the radiator and battery.

vorgath

oh ok .. those things ok ... I've seen them in Summit & JEG's ok

aaron7

iTrader: (7)

Battery relocation kits that Summit sells are 2AWG, would that be good enough? The kit is under $70 for everything, including the battery box!

vorgath

I'm going to go with 1/0 when I relocate my battery, heck since I got an Optima Yellow now I guess I won't have to go with a selaed box anymore

[R]ogue

aaron - according to the chart I was given which meets SAE standards over a 20 foot span you are technically capable of passing 200 amps through 4 AWG ( in my 14 years of experience I have found most GM starter motors in good shape to draw around 100amps with an inrush around 140 ) so 2 AWG should be way more than enough. so... if your wire also doubles as the conductor for your high amp alternator again 4 should be enough and 2 would definetly be playing it safe.

NeedAZ - I'm still trying to figure out what you are saying - you are obviously no dummy - I've even talked to a few of my respected peers however and we are all at a loss to why you say you can't pass more amperage at a higher voltage through the same wire ???!!?!!!??!?!

i do understand about the continous duty needing bigger wire because of resistance increases from the heat. i guess i assumed that the SAE chart figured in heat into their equations since they already figured voltage drop over distance into their recommendations.

and lastly NeedAZ - what would your thoughts be on paralell wiring? since circuits in paralell have less resistance than either individual circuit theoretically you could use the smaller wire then recommended in paralell right?

NEEDAZ

aaron, if your going to be running a lot of of aftermarket electrical stuff I would (my opinion) run 0, you can get away with 2. Maybe it's just best to say 'I'm not saying 4AWG wouldn't work, but 0AWG would work best, or would be about as idle as you would need to get'. How's that?

Well, let me start by saying in my post above I was thinking that was in reference to the thermal limits of the wire (which in most cases is the thermal limits of the insulation, but as wire ages other things can come into play. Corrosion, oxidation, and stress points can drastically raises the resistance of a small section of wire). I shouldn't have said flat out wrong. If you just look at an acceptable percentage of voltage drop, yes. The resistance of the wire would stay the same, so as you pass more current though the wire, the voltage drop would go up. If you look at this voltage drop as a percentage of the applied voltage and you double the voltage, you can double the current, have twice the voltage drop, and still have the same percentage of voltage drop. You can't just keep doubling the voltage and doubling the current. Until you hit what ever current would exceed the thermal limits of the wire. What make the wire get hot is the wattage that the wire would dissipate because of it's resistance. The wattage is the voltage drop across the wire and the current through the wire. P=IxE. When you said "as ya'll may already know the higher the voltage the more current you can flow through the same size wire" You can't just up the applied voltage and pass more and more current through a wire.
Check out this page. On the right, goto #16 Wire.
Basic Car Audio Electronics
A couple of things to keep in mind when read this page. The "Speaker Wire Calculator" Is vary misleading. It's simplified to make the point, but reactive loads like speaker make things a little more complicated then it makes it look. Same thing for the "Power/Voltage Loss Demo", a bit generalized/ simplified. But way down there is a lot of good info about wire cross section and it's affects on resistance and current handling. The 300 Circular Mils 'limit' they suggest may be on the vary safe side of things. But at less then 300 Circular Mils the current will start to heat the wire, maybe only a little but it's power lost to heat. From a design stand point you try to keep things as close to ambient as is practical. But then cost restraints and... come in. Let's face it, even cars with small electrical add-ons can benefit from upgrading the BIG 3. Noticeably brighter head lights and all. Just because it works, doesn't mean it can't work better. Have a look see around at the benefits some have had by doing the BIG 3 upgrade. It's a great example.

[R]ogue

NeedAZ - thanks dude, the picture is getting clearer... I appreciate the effort you made to explain this. I'm going to be wiring up the amp in my 84 bird this weekend and yea i really can't and won't argue that there is nothing wrong with bigger is better when it comes to wiring other than added expense