Question About Wiring Upgrade for New 150amp Alternator
 

I just ordered a 150amp alternator from Eagleelectronics on ebay. Others on here recommended them.

I installed a Webasto heater recently and a couple times I have been left with a dead battery (after I used the heater, started the car, took a short trip and then tried to start the car again). I was going to go with the 120amp version, but the 150amp was only $15 more and I have injection line heaters and I have a 15amp ceramic heater sitting on the shelf that I have considered installing. So I figured I might-as-well do the 150 vs the 120.

I have read through several alternator upgrade threads. I realize that I need to upgrade the wiring from the new alternator to the junction box.

My questions are-
What size wire would be sufficient from the alternator to the junction box for a 150amp alternator? What types of stores carry this wiring?
Do I need to upgrade any other wiring in the system? How about the ground strap or starter wiring?

Thanks!
-Ryan

2-0 wire ought to handle it... try an audio installation store. I think walmart has some decent cable at good prices in their speaker section... andy took some good pics and posted them here I think he is still the #1 most replies thread... at the end of his thread he posted some links to other projects of his and one of them is his 140amp alt wire upgrade... good info there.
http://www.peachparts.com/shopforum/1251255-post7.html

Yep, that was one of the threads I found, but the problem is his photos are gone. I'm assuming they are not being hosted anymore so the links/pics are dead.

Here is another I found-
http://www.peachparts.com/shopforum/car-audio-multimedia/53236-installed-143a-alternator-my-w124-86-95e-class-photos-2.html?highlight=alternator+upgrade
He is using 2- 4 gauge cables to the junction box for a 150amp alternator. It is on a 124 though, but I am guessing it does not matter. Is the junction box ont he 124s and the 126s the same? So perhaps I should use 2-4 gauge wires. I haven't checked my juntion box, but I am assuming it splits into two hookups there as well like it does on the 124s?

I want to do this right.

that block looks nothing like any of my 123/126 cars...

My first question, in regards to your problem, is how old is your battery? and what amp rating, how much reserve?

In regards to your 150 amp wiring, with such a short distance 2ga. should be more than enough.

Yes, any of the 0 gauge wires would be overkill for under 3 feet.

Battery is less than two months old. I would assume that the battery did not fully recharge and thus having trouble starting, but there may be a new battery drain that has developed. The battery is the Duralast from Autozone. Don't recall the specs offhand but I believe it is the DL-49?? I know the problem doesn't lie in the battery itself. Hopefully the new alternator fixes it, if not there is obvioulsy a newly developed short somewhere.

Okay, looks like 2 guage it is.

FI, I know you upgraded the starter wiring, do you think it would help at all in (cold) starts? How about the ground strap? Well I'm at it, if it is beneficial, I might as well do it all.

Yeah, I would upgrade the ground wire from the battery to the body and put a nice ground strap THERE to the engine. I don't like the way MB puts the ground to the body, then another strap somewhere else to the engine. I want TOTAL ground connectivity through the copper to the engine!
obviously, MB's design is adequate for their oe wiring, but for the upgrade, I'd upgrade it all.
and while I agree a short distance makes it fine for lower capacity wire, I would want 0 or better for 150A... it gets MIGHTY hot near the turbo, and heat lower's a conductor's capacity...

A couple of points:

The starter cable and ground cable are capable of well over 100amps as evidenced by the starter cranking current passing through. If you want more starter current available, and have an adequate battery, then upgrading the engine ground strap and starter cable makes sense.

As far as the 150a alternator goes, I'd be happy with 2AWG to the junction block, and to the battery from the junction block. An easier method would be to run two 2AWG wires from the alternator; one to the battery and the other to the junction block or 2AWG to the junction block and 4AWG to the battery.

The ground strap to the battery isn't necessary for upgrade either IMO unless you're looking for more starting current. The battery isn't capable of taking 150a of charging current without melting, it will only take perhaps 30a for any period of time and decreasing from there.

The 150a alternator will put out 150a if necessary, a little of it will be charging the battery, but the bulk of its output is available to car systems while the engine is running. Most cars will never see a continuous draw of 100a or more, large stereo systems included, although resistance heating fuel tanks does tend to create some demand above the norm. One of the significant advantages to the larger alternator is its ability to put out more amps at idle and also for extended periods when hot (alternators are de-rated at high temperatures), and the peak high-current for initial charging & systems when first started in the cold.

I only replaced the wires because my cable was loose at the starter, I had some big wires laying around and a day of nothing else to do. Starting is a little better especially since I have that big 2/0 ground wire strapped directly to the starter's mount bolt but it will always be limited by the wire gauge between the solenoid and motor.

A quality rebuilder shouldn't have a problem rewinding the motor with more coil turns and use a larger solenoid-motor strap (They often do it uprating alternators). As long as you don't go nuts cranking it for minutes at a time it would probably come close to what the Mean Green starter can do but with better reliably.

I used 4-AWG for the alternator-starter, starter-battery, and engine ground, and run a stereo. Everything works like a champ.

How many amps does your alternator put out?

Here's some great info on the alternative alternators.
http://www.w124performance.com/images/W124_stereo/alternator/

This is an excellent post!

Thanks, but that is the same install that I linked in post #3. It is for a 124, which is why I asked the questions I did in post #3.