OK, I know this issue was resolved only a short time ago, but I can’t find the thread. So… I’m upgrading to a Powermaster 12si 150 Amp alternator. According to the Powermaster literature, the charge wire should be at least 6-gauge but the appropriate wires in my new reproduction engine wiring harness are only 10-gauge. I’m considering running an additional 10-guage wire from the alternator to the starter, but I don’t know if having two 10-guage wires running in parallel equals one 6-gauge wire as far as current capacity goes. So, maybe running a 6-gauge wire from the alternator directly to the battery would be best? If so, do I still hook up the stock 10-gauge wire (in the harness) to the alternator? Thank you in advance for your advice. NOTE: Alternator output and power-wire gauge revised 3/25/22.
http://www.buickperformanceclub.com/alternat.htm https://www.v8buick.com/index.php?threads/12si-alternator.367994/
I used the instructions from the buickpermoanceclub.com, above, to install a 94 amp Duralast 12si nearly 20 years ago. Part number DL7194-6-3. I'm simply running a 10 gauge from the alternator to the battery. Installation is simple: buy the pigtail, do the rewiring (very easy), grind a little nub off the back of the case (not visible), swap the serpentine pulley for your v-belt, drop it in place and drive. Total time - maybe 40 minutes.
First of all, thank you for the responses, gentlemen. However, I apparently didn't do a good job of explaining what information I was looking for. So, here goes: 1 - I already performed all of the revisions to the reproduction engine wire harness noted in the Buick Performance Club article referenced by Mr. Bell above as they apply to my set-up (Full 12v to coil, Stage1Restoration Alternator Conversion Wire, etc). So, I think I'm OK with the harness EXCEPT for the stock-size 10-gauge wire that runs from the alternator to the starter, the now-bypassed external voltage reg and the firewall connector. 2 - The Powermaster literature advises use of a 6-gauge charge wire for a 150-Amp alternator. So, what do I do to compensate for the stock 10-gauge charge wire? A - Run an additional large-gauge charge wire from the alternator to the starter in parallel with the stock 10-gauge charge wire? B - Run a 6 or 8-gauge charge wire from the alternator directly to the battery + post in addition to the stock 10-gauge charge wire running down to the starter, etc? C - Run a 6-gauge charge wire from the alternator directly to the battery + post and cut or tape-off the end of the 10-gauge charge wire that normally attaches to the alternator + post? Anyone know for sure? If so, I sure would like to hear from you. (NOTE: I revised the amperage of the alternator from 100 Amps to 150 Amps and the recommended charge-wire size from 8-gauge to 6-gauge in my original question.)
I am 90% certain you should NOT run two wire together instead of one big wire. The problem is if one wire fails, now you have meltdown. Twice the wires equal twice the opportunities for a failure, ie short or disconnect. That is a lot of power coming thru, I would probably replace the existing 10 ga wire with 4 ga. and call it good. What is the big draw on the system that requires the extra power? Stereo or just power accessories. What gauge wire is your main battery cable? 00,0, 2, 4?? That is a big ass alternator, man.
Mine was a 1 wire setup. I ran the recommended wire from the alternator to the battery, but also used the stk smaller wire. No issues for a very long time
Some good info and a chart here http://www.offroaders.com/technical/12-volt-wiring-tech-gauge-to-amps/
The General has gotten away with using under sized wire, because its too short to cause much voltage drop, and the current only peaks just after the engine is started and a slug of energy needs to go back into the battery. With a combination of heavier continuous loads and a big alternator, the wire size needs to go up. I would use only one wire like those above, 6 ga welding cable is my choice as I gradually upgrade my cars. For a 150A I would use 2 ga, but why is that needed, and normal vbelt setups will slip terribly if it is actually called on to deliver 150A. good luck, Bruce Roe
The goal is not to charge the battery but to get amperage to whatever load you are driving. If you run a large gauge wire to your battery, you'll be able to charge your battery at 150 amps, which would never be necessary or possible unless your battery had an internal short, then it would explode. If you run it to your battery, you will still have a 10 AWG wire going to your load from the starter. You need to get that heavy gauge wire going directly to the fuse block if you want to use all that amperage. The people who have connected it to the battery and say it works probably have never fully loaded the alternator, if they did, that 10 AWG from the starter to the fuse block wire would have melted.
Not saying my method is the absolute correct way, but here it is. Only a 105 amp alternator on my car, but the concept is the same. I ran a 6ga wire from the back of the alternator to my battery. From the battery, more 6ga with an inline 40amp maxifuse (you would change this to whatever you need depending on ultimate load) to a power distribution block,. The block directly powers the MSD and headlights (via relays). From that block, I then run another 6ga to the back of the car to feed the stereo amp, powered sub and electric fuel pump. The problem with running a new big wire to the starter, then a new big wire to the old fuse block, is that the fuse block itself was never designed to handle more than probably 30-40 amps total (probably less than that). Finally in an effort to avoid ground loop noise I also ran a large dedicated ground to the back of the car from the battery for the stereo stuff and fuel pump. Thinking as I type, I might actually be better off, and safer, to run the big wire from the alternator directly to the distribution block, with the maxifuse inbetween, and not connecting directly to the battery.... Will have to think that over during the next few weeks before the season starts....
Hey Jon.... I think you're correct, so I'm tossing that idea out. Thank you. Hey Phil.... I'm going to send a PM to you. Thank you. Jon, Bruce, Phil, et al, I'm falling back to my original plan to only use the 100-Amp Powermaster alternator that's installed (mocked up, really) on the engine. Thank you all.
Well I guess that would be determined by where their load is coming from. All my high amp add ons.....2 larger fans that pull 40 amps combined when running, a fuel pump that draws 20 amp when running, electric water pump, oil circulation pump etc.....all of this runs right off the battery.....not my fuse block.......so I'm worried about putting 150 amps to the factory fuse block.......and if you put to much through that you will melts. Now the power that runs the control side of my relays does come from the fuse block.....but very little load there. I know if I go to a weekend race I cab run all 3 days, as many runs as I came put on it and never worry of charging.....even in the middle of summer where these accessories run longer to get the car cooler....... I have wired several street rods the same way and they have never had a charging or starting issue.........can i say its the rightist way.......no......but it has worked for me and them for years without issue.........just added the large gauge from the alt to the battery along with the factory and ran my heavy load fed from the battery
I have 150 AMP alternator with 4 gauge to starter lug, and 1/0 gauge from battery to "Flaming River" electrical battery disconnect to starter lug (and same gauge for negative), standard fuse links to harnesses, and 10 AWG off alternator to regulator. I also use fused junction block off the battery disconnect to power the fans off relays triggered by coolant temp switch and EFI ECU. (and multiple ground/bond straps and wires as well as serrated washers everywhere) Duplicated on both my 64 and 68. Resistance (and time) are bad on electrical systems/accessories, as are poor grounding/bonding. Big fat wires and the battery make for good distribution and the battery is a good "noise filter" as well. And I order custom cables from here. Excellent product, and great for anyone doing engine swaps and other custom mads and stuff. https://www.custombatterycables.com
I for one am wondering just how much current can be pulled, before belt slip is unacceptable? I had to revise my belts to deal with a 70A diesel alternator. Does a serpentine belt help a lot? If the currents are really getting that high, a setup like this might be adventageous. It was factory on my 62 and others, this conversion is on a 77 Delta. The starter cable makes a stop at this terminal, and all other loads draw from there. Nothing else going to the starter BAT terminal, all other wire is moved away from the heat, vibration and water down there. Notice the fusible links, that is good protection to have feeding any reduced size wire. Makes it far easier to service the starter too, just disconnect the bat and solinoid wires on the fender, and drop the starter with the 2 wires still attached. Bruce Roe
I agree, if you are doing something like that you would want to run a separate power buss to the relays controlling those items. Your relay actuation current is typically 20 ma which is negligible and can run from the accessory circuit. The author of the post did not state what this giant load was, assumed it was a stereo, hydraulics or something.
Hey guys…. Sorry for taking so long to get back to you. Thanks mostly to you, I decided to stay with the Powermaster 100-Amp alternator for my ’72 455 Skylark Convertible. I still have a question, though. But first, a little background info: I’m trying to keep my engine bay (including the engine wire harness) looking as close to “early-1970’s stock” as I can. That means no “bling”, power distribution blocks, etc. Right now the electrical system is stock except for the following: Dave’s small-body HEI distributor, electric choke on my QJ, internally regulated alternator, DOT-approved halogen sealed-beam headlights and a not-very powerful Custom Autosound AM-FM stereo/CD player hidden under the front seat. I may soon be installing one or more of the following accessories if desirable/necessary: Electrical “pusher-type” cooling fan, fuel pump and, possibly, throttle-body EFI. NOTE: Powermaster suggests running an 8-guage wire from their 100-Amp alternator Positive terminal directly to the battery. QUESTION: If I follow Powermaster’s advice, do I also need to keep the stock 10-ga wire that runs from the alternator down to the starter? I ask because the noted stock 10-ga wire branches out to 3 or 4 other locations, including the starter… Which is also fed by the stock battery cable. I mean, shouldn’t all of the current produced by the alternator be fed directly to the battery and then on to the starter? That’s it! As always, thank you for your help. I’d probably still be stuck on square one if it wasn’t for you all.
