I bought a (Supposedly) new 200 Amp alternator from E-bay.
I cut a 4 Ga. battery cable end and attached a 1/4" connectors to run from the back of the alternator to the horn relay.
I got cable left over could I also run wire from the back of the alternator to the battery like you would do with 1 wire cables?
Will I gain anything or am I wasting my time?
Thanks
joepenoso

 

The horn relay stud is wired to your battery already, so no you will not gain anything.

 

Are you quite serious?

You are installing a 200 Amp alternator?

What kinds of accessories do you have that are going to draw that much juice?

On to your questions:
1. You are aware of the circuit that you need this 200A current to follow, are you not?

It must get from the alternator to:

1. Your battery, and
2. Whatever accessories you are running that draw that much current.

This means that you must run adequate wire for every inch of those paths, or the wire that is there will melt when you put 200A through it.

The charging circuit for your car (which I believe is a '71 Cutlass) goes:

• Alternator output post
• Horn relay power post
• Starter motor big post
• Battery

That's not counting the path of current to any high-current accessories you have (mechanical fire engine sirens, search lights, welding apparatus, etc.).

In order not to burn up the existing wires, ALL of the above wires must be replaced with wires that can handle 200A.

In order to determine the necessary wire size for a given current, you need to know:

• The current (We know that, 200A)
• The voltage (We know that, 14.5V)
• The wire material (We know that, copper),
• The desired voltage drop (for a charging circuit, I'd go low, like about 2%), and
• The length of the wire (from alternator to horn relay to starter - the wire from the starter to the battery should be heavy enough.
  Alternately, you could go from the alternator to the horn relay to the battery directly, cutting out the starter motor portion of the run.
  You also need to know how much of a run you have for your high-current accessories).

If we figure the distance from the alternator to the horn relay, and then to the battery, I think that's about 8 feet of wire (maybe a bit less, depending on routing), SO...

• Obtain your Voltage Drop Index thusly:
  (Current [in Amperes] X Distance [in Feet]) / (Voltage Drop [in whole-number percent] X Potential Difference [in Volts])
  
  VDI = (200 X 8) / (2 X 14.5) = 1600 / 29 = 55, so
  
  VDI = 55
  
• Find your VDI on a Wire Sizing Chart, such as this one,
  making sure that your required current (200A) does not exceed the listed Ampacity:
  
  
  In this case, your VDI of 55 is close to the listed VDI of 62, which corresponds to an Ampacity of 195, which is close enough.
  This corresponds with a copper wire gauge of 00 (or "2-0"), which has a cross-sectional area of 67.4mm, which means a conductor diameter of about ⅜".

The 4ga wire that you used has a cross section of about 21mm, and a diameter of about 0.2", which gives it roughly a third the current capacity of the wire that we have just figured out that you need for your 200A alternator, and, in fact, your 4ga wire is rated up to no more than about 60A for power transmission.

So, you need to rip out the 4ga wire that you just installed, and install 00 wire from the alternator to the horn relay, and then to the battery, and also to any accessories that you might be using that could draw 200A, unless they are farther away than 8 feet, in which case you will need to run 000 wire to them.

See? Easy!

- Eric

edit:
NOTE: I have found references that recommend wire sizes as low as 2ga for this run, for higher acceptable losses and non-continuous power flow - you need to assess the power that will actually be flowing through the wires and decide on the best solution.

 

I am curious as to why you need a 200 amp alternator. Chances are good you will never have the 200 amps flowing from the alt anyway unless you have an inverter. If the wire from the horn relay is large enough to handle the 200 amps, adding a wire will not help, but if it is too small a new wire will help and it won't hurt anything if you put it on anyway. You may need to upgrade any wires that may be getting the higher amps that the alt is intended for. You may find that the 200 amp alt will put out even less at low RPM than the original alt, but that will depend on the type of alt it is and how it was made to put out 200 amps.

 

I have a 60 amp alternator and run 20' of 4 gauge for it, and 00 from there to the trunk mounted battery and up front to the horn/junction block. It is a race car with the NHRA required battery shut off in the rear bumper.

 

Looks like Eric is way ahead of me. Follow his directions they are detailed instead of general like mine. I would add you should determine what amps the circuit will draw to determine wire size and again I doubt if you will ever see 200 amps being produced unless it is a huge load and the RPM are very high.

 

Eric your theory would be correct if the load on all those wires was 200 amps. A battery has 650+ so would you want all the wires in the car sized to handle that? Wire sizes are based on the load of each individual circuit. 4ga is good to 200A up to 7 feet.

http://www.powermastermotorsports.com/charge_wires.html

 

It all depends on whether he expects to use the 200A continuously or intermittently, and where he needs to direct it.

As I said, he needs to run the right wires for any accessories he has that he expects to draw 200A. Obviously, accessories that draw less will require smaller wire gauges.

However, if he is planning to run 200A from his alternator to his battery, 00 is the correct gauge for low current loss for that run.

If he runs 4ga wire, he will have a 5% voltage loss, which means he will lose 0.7V on the way to the battery.
Since the difference between a charged battery at about 12.5V and a normal charging voltage of about 14V is about 1.5V, that 0.7V loss is significant.

- Eric

 

I don't think he will come close to drawing 200A on any or all the circuits combined on his car. The recommended wire sizes already have load a fudge factor built in. I agree 200A is way over kill for a car, but won't hurt anything. Any accessories need to have an appropriate fuse in line as not to create a Chernobyl like melt down in case of a short.

 

Not if it's a stock car. But if it's a stock car, then why would he need a 200A alternator?

I based my recommendations on the ASSumption that there was a reason for him to have a 200A alternator in the first place - obviously, my ASSumpton could be baseless, and he could be running a 60A charge into a normal battery for 45 seconds after 3 seconds of cranking whenever he starts, and other than that not doing anything but powering the stock accessories, in which case, he probably doesn't need to change his wiring (or his alternator) at all.

- Eric

 

It would be nice to know the reason for a 200 amp alt. I would also recomend a volt and amperage output test both with a load and no load on what is in there now and again after the change is made.

 

It claimed to be 200 amps.............................maybe Chinese amps which for hyperbole are considerably weaker than usual ones.
The alternator sold was advertised for 200amps. but alternators rarely put out what they advertise.
Output drops as heat builds.
Alternators are not meant to be run at full capacities for long length of times....................................The alternator was selling for a price I couldn't refuse since my stock alternator is starting to squeal like a stuck pig when the dual electric fans start up.
The alternator is just like the one below except it was made with 3 wires
http://www.ebay.ca/itm/NEW-ALTERNATOR-CHROME-GM-CHEVY-HOT-ROD-12-Clock-Plug-Position-HIGH-OUTPUT-200AMP-/290685553079?pt=Motors_Car_Truck_Parts_Accessories &fits=Model%3AMalibu%7CMake%3AChevrolet&hash=item4 3ae3589b7&vxp=mtr
Ok I'll admit it I'm like a flock of birds,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,you 'll hear cheap!! cheap!! cheap!!
Anyhow to the original question will running a second heavy duty 4 Ga. cable from the battery to the horn relay be useful?
thanks
joepenoso

 

Sounds like a loose fan belt.

- Eric

 

Checked that.................................The alternator light comes on when squealing
thanks
joepenoso

 

Again, loose fan belt.

Belt slips, squeaks, alternator doesn't turn, light comes on.

 

Which also corresponds with the idea of a loose belt.

By the way, what's with the All-Bold-All-the-Time? IT'S ALMOST AS BAD AS ALL CAPS.

- Eric

Joe - JINX!

 

No offence intended ......sorry for the bold..........I just like the way it looks. I checked the belt after squealing ( Tight)............... I guess I will leave the original alternator there and tighten it again, maybe even put some belt dressing to make sure it isn't slipping.
Thanks for taking the time to answer the question. I think sooner rather than later I will be putting the high AMP alt. on. I won't be putting a fused link from back of the alt. to the horn relay. The battery to the relay is about 60"s. I will run a 4 ga. wire from the battery to the horn relay..............should it be fused?? I don't believe the alt. puts out 200 amp continuously........................I guess you will find out if I write back telling about melted wires.
It's raining out and I got to take the kids somewhere to play........................Chuck..E.....Cheese or McDonalds playground. They have cabin fever.
thanks
joepenoso

 

i've just one thing to add to this, from the ebay page: "... We recommend installing a fused 4 gauge main charging wire ..." emphasis on fused.
without some sort of protection in the alternator output wire, if a short occurs, you will have chernobyl under your hood.

ahh, the fun of high-current under-hood wiring, if not done properly, the results are usually disastrous.


bill

 

I would discourage you from using belt dressing, it doesn't solve any problems, at best it hides a problem temporarily. The belt could be glazed from previous belt dressing or slipage, I would replace it first......

 

Thanks
joepenoso

 

With the engine running use a wire brush and CAREFULLY press the bristles against the belt to rough up the surface a little and remove the glazing. The belt needs a little friction to grip the pulleys. Also, the belt shouldn't bottom out in the pulley grove, it needs to grip the flange of the pulley. Don't use belt dressing, thats like putting a Band-Aid on a gunshot wound.

If you expect to get 200 amps of alternator output to the battery you need to have cables big enough to carry the current from the alternator to the horn relay, and from the relay to the battery. I cant imagine any car needing that much current.The largest alternator capacity in new cars I'm aware of is 160 amps, that is expected to power electric fans, heater seats and windows, electric defrost, and other accessories. Assuming that alternator is capable of that much current I would be surprised if a factory belt wouldn't slip on the pulley under max load.

 

I might do this as a temporary fix on the highway to get me to an auto parts store, but that's the only reason.

 

Hi Joe:
Here is my suggestion which is a combination of the comments above and experience with running 100 AMP radios from a car.
Install a new 4ga RED wire from the alternator directly to the battery (not to the Horn Relay).
Install a new 8ga RED wire from the battery to the Horn Relay.
Keep your existing Alternator wire; just disconnect it from both the Horn Relay and the Alternator and tape over the ends securely.
This will allow you to revert back later if needed.

You will need a few parts from a mobile audio sound store to make the solution safe. New Stereos can consume up to 100+ amps.
The mobile stereos stores will have the high current parts you need and the technical support to explain how to install them safely.

The goal here is to protect your existing wires and to avoid major modifications to existing wires.
The new 200 amp alternator will not be running at 100% capacity, I am guessing you may only peak at 100 amps for a few seconds.
The rest of the time the alternator will be under 70 amps (assuming a 71 CS with AC??).
You will need an In-line bullet fuse holder with a 100 to 125 amp fuse.
Install the bullet fuse holder at the Battery end of the 4ga wire. This fuse will protect your system from an Alternator Short.
Attached the 4ga wire to the battery with a new multi-wire post connector from the Stereo shop.
Remove the old remains of the 10ga Battery to Horn relay wire and dispose of it.
Install the new 8ga wire between the Horn relay and battery (this wire usually does not have a fuse).
Use the correct color codes (Red for battery).
Use good quality lug connectors and crimp and solder.

The reason I suggested this format is for the following reasons.
The new 4ga wire connector is too big for the Horn Relay.
So just connect it to the Battery directly.
Alternators make noise; the direct battery/alternator connection will do a better job at absorbing alternator noise. The battery will act as a noise capacitor.
Then new 8ga wire between the battery and Horn relay will hand a little more power than the old 10ga wire, and still fit onto the Horn relay.
If in the future you want to build a stereo to support a concert, you will connect the super sterore directly to the battery and never to the cutlass dash fuse block.

 

One other thing you could have a worn out pulley or a bad bearing I would check those

 

miles71,

why would you recommend a 100 to 125 amp fuse for protection of an alternator that can put out 200 amps? that does not make sense. you gotta consider the "worst case scenario".

in addition to crimping and soldering connections, self-sealing heat shrink tubing should also be utilized, for a long-lasting job.

you can find correctly sized ring tongue terminals-you just have to look a bit. a good hardware store will have them in bulk.


bill

 

If your belt squealed before, wait until you try to tap 200A of power out of it!

A belt can only do so much. The upgrades for increase power transmission are typically
more belts- double is not unheard of for automobile alternators
wider belts - not practical here
larger pulleys all the way 'round - again, not practical here.
Multi-V belts like the common serpentine - "just" change all the pulleys to suit, and put 'em all in one plane.

 

Hi Bill:
I suggested a 100 to 125 amp fuse because based on the information it appears Joepenoso will be requiring just a normal load of under 100 amps. A 100-amp fuses can actually pull 10-15% more for a few seconds before popping. The fuse size can be easily increased as needed.

Octanina also brought up a good point. Most alternators over 100 amps, use multiple ribbed or multiple belts. A single stock V-belt on a 200 amp alternator would be quite at load less than 80 amps, and may start to slip / squeal above 100 amps. The more amps, the greater the belt load and horsepower required to spin the alternator.

Horsepower loads (all values are approximate assuming 700 watts per HP):
To spin a 100 amp alternator at full load would require approximately 1.9 HP.
A 200-amp alternator at full load would be approximately 3.8 HP.
The stock GM 63-amp alternator requires less than 1.3 HP Belt Load.

 

miles: let's say, for the sake of an example that the original poster's 200 amp alternator is putting out 125 amps for more than a few seconds. what is going to happen when that fuse pops? here's what's going to happen... the fuse pops, the output power now has no place to go and the output voltage jumps massively and fries his alternator. depending on how it fries it may start on fire internally(i've seen that). fusing a 200 amp alternator at 100-125 amps is poor practice, at best. proper fusing would be a slow-blow type, at 250 amps. you don't fuse a circuit at what you think it might need, you fuse it for what it can do safely, this includes the supply, the wiring gauge, and the possible load.

also, using your number for hp load vs output watts, a realistic number would be derived from the possible charging voltage x amps which would, at 100 amps output, be up to 2.1 horsepower, or 4.2 hp at a 200 amp output. this is at a maximum charging voltage of 14.7 volts(cold output). the hp load drops a miniscule amount when you get to hot output voltage, which is typically 14.2-14.5 volts.

octania's point is quite valid regarding belt slippage caused by high output alternators.


bill

 

The 4.2 HP figure is accurate, as far as the maximum output of the alternator goes, but remember that no system is 100% efficient, and most are pretty darned inefficient, so you've got to figure a minimum of 5 HP input, if not 6.

- Eric

 

Joepenoso, how did it turn out?