Increasing Gauge Size of Alternator Battery Wire
 

I am installing a 150 amp alternator in my 66 Lemans. It has/will have dual pusher Spal fans, 340 LPH fuel pump. GV OD, amplifier, Dakota Digital dash, Progression Ignition. The car has a brand new M&H engine wiring harness with 12V wire for HEI and upgraded for an internal regulator.

The CVF alternator I bought may be used as a 3-wire or 1-wire. Since I have to use a 6 gauge battery wire for the alternator is it OK to attach the 3 engine harness wires to the alternator as the factory did, and add the 6 gauge wire in tandem, to the starter’s battery post?

Or should this be wired in the 1-wire configuration? If so, is it OK to run the wire to the starter’s battery post.

I’d prefer to do it as a 3-wire so I can make use of the new engine harness.

I'd hook the alternator up as a 3 wire system and make sure the sense wire source is on a switched circuit somewhere down near the fuse box, not just a jumper from the alternator's sense pin to the alternator's output lug.

Speedway has a wire size chart (below) that calls for #4 wire for a 5 foot or less run at 150 amps from alternator to battery, increasing to #2 wire for 5 to 10 feet.

In the real world I'll bet your alternator will seldom if ever put out over half of its rated 150 amps.

https://content.speedwaymotors.com/D...ernator-lg.jpg

The M&H harness is set for a 3-wire alternator so no jumper wire needed. Are you saying I can't connect that as normal and add the 6 gauge cable? CVF said 6 gauge is what I should use - also, I mistakenly said it's 150 amp - it is 140 amp.

Adding the #6 wire will help. I'd make sure the two wires terminate the same place on both ends.

Thank you!

The factory wire goes to a junction as I understand it. Not sure where it goes from there.

I agree on the 3-wire installation. Also with running the 6ga. from the alternator to the cable terminal on the starter.

That is how Mark Hamilton @ madelectrical.com suggests, and I've had excellent results from following his suggestions over the decades.

Thanks Lee. So in your install, you kept factory style 3-wire connection and just added the heavy wire as an additional wire?

Did you have to make it a certain length so it matched that of the factory harness?

Any overcharging the battery with this set up?

Will,

MOST of what I know about electrical systems, has been gleaned from reading Mark's information. He also has a couple of small books, but excellent information in them.

Here is a link, there are actually 3 pages of info here, so be sure to click through all 3. I started typing, then realized it is better to just give you the link :-)
http://madelectrical.com/electricalt...hreewire.shtml

To answer your question, I have sometimes replaced the factory charge wire, and other times added a second wire. I route the wire up from the starter, then trim to the length I want at the alternator. I use a set of Thomas & Betts forged steel crimpers for wires up to 10ga, and have a handheld hydraulic crimper for heavier gauge wires. For power wires I typically use uninsulated terminals, do the crimp, then solder the connection, and finish with adhesive-line shrink tube.

I've had AGM batteries (XS Power and Braille) last up to 10 years, routing this way.

Something else from Mark to consider: http://madelectrical.com/catalog/tb-1.shtml

Thanks, Lee - I've looked at the madelectrical site and its great info. I may get that book!