alternator upgrade... how many amps should i get?

[marshallfry01]

I need to order an alternator for my 69 383 car. The ammeter has been converted to a volt meter by redline gauges. I'll also do the headlight relay upgrade so all the power won't be going through the switch. All wiring is new on the car. (M&H original style) Everything on the car will be basically stock except it will be electronic ignition (mopar orange box) and the original thumbwheel AM radio has been retrofitted with modern internals... 45 watts I believe, nothing crazy. I'm also planning on putting a low profile 8 inch subwoofer under the drivers seat that has a built in amp. I think it is somewhere around 150 watts rms.

Now for my actual question... would a 1wire/internal voltage regulater 90 amp alternator be sufficient for what I need? I know the original 60 watt is way underpowered but I don't want to go too big since it's powering a small sound system. No electric fans, no digital gauges, no fuel injection, no electric fuel pump, no power windows/locks.

[b5blue]

Think of EVERYTHING that could be on at one time. Lights/defroster blower/wipers/stereo/blinkers/brake lights all while running the motor.  https://www.qualitypowerauto.com/pages/ChryslerMegaAmp.php

[Dino]

I had a 90 amp, but after additional upgrades it wasn't enough so now I run a 120 amp. Go as big as you can.

[marshallfry01]

I had a 90 amp, but after additional upgrades it wasn't enough so now I run a 120 amp. Go as big as you can.

I guess that's where I'm getting lost... how big is too big? I know a bone stock wiring system can't handle big electrical loads... but I've eliminated that weak link. If I go with a 120 amp, what would happen if that is too much? Or do I not have to worry since it has an internal regulator?

[Kern Dog]

Nacho usually chimes in when electrical questions are posted. That guy is pretty sharp.
My understanding is that the regulator will limit the alternator output to only what the system needs. I swapped in a Tuff Stuff 120 amp alternator and then used an adjustable regulator to keep charging around 13.8 volts.
With a stock type rebuilt 63 amp unit, the voltmeter would get below 8 volts at idle with lights, the radio, A/C and the vacuum pump running. Now it idles at 13.8, runs 13.8 at 2000 rpm and at 6000 rpms.

[Gold Rush]

That is all good info and on track.  Think of the alternator as one big electron supply.  If your system asks for 100 amps of power but the alternator only has 63 amps available the system is getting starved some.  If your alternator is a 120 amp unit then there is some to spare.

The advice b5blue gave is your first step.  Just depends on what all you are needing.

[b5blue]

  The feed through the Alternator gauge was the weak spot for charging the battery if it was mostly discharged. That path of flow could draw big amps through the gauge. You said you did the voltmeter swap so not an issue.
  I also did the "Fleet upgrade" and fused my Denso 120amp output to a mini panel. Call the guys in the link.

[Nacho-RT74]

Nacho usually chimes in when electrical questions are posted. That guy is pretty sharp.

Becarefull with that affirmation! Mr. Renton can be sensitive to that

[Nacho-RT74]

As mentioned. You can install a 500 amps alt, but if the system demands 60, the alt will provide just that.


Your batt feed 100 amps to to the starter motor throught a 2 gauge wire the same that feeds the 0,2 amps the glove box light requires with a 16 or 18 gauge wire... and the glove box light and wiring won't blow because you have 500, 700, 900 amps batt.


The deal here is try to get the best output as posible at the lower speed as posible. That will guarantee your charging system will be relaxed most of the time with a battery barelly needing charge and the alts feeding all the car/accs requirements as posible.

[Kern Dog]

Nacho usually chimes in when electrical questions are posted. That guy is pretty sharp.

Becarefull with that affirmation! Mr. Renton can be sensitive to that

That guy is a total jerkoff.

[Nacho-RT74]

Forgot to say...

In other words, amperes are SUCKED OUT by devices FROM the power source, not PUSHED IN BY the power source.

So you need a source able to PROVIDE what the baby needs to suck or will be constantly crying.

The deal with high amp alts is... they are ABLE to provide they spec's power at certain speed, but, stock alts just sources at idle around half of that (depending on pulley size) then the curve begins to increase with speed.

HiPo Alts are per what I have found, able to provide at idle around 2/3 of its max ouput. That's a cool 50% increase more than the stock alts.

I'm always talking about original Chrysler alt design and their HiPo versions/options on market nowdays.

[Derwud]

As mentioned. You can install a 500 amps alt, but if the system demands 60, the alt will provide just that.


Your batt feed 100 amps to to the starter motor throught a 2 gauge wire the same that feeds the 0,2 amps the glove box light requires with a 16 or 18 gauge wire... and the glove box light and wiring won't blow because you have 500, 700, 900 amps batt.


The deal here is try to get the best output as posible at the lower speed as posible. That will guarantee your charging system will be relaxed most of the time with a battery barelly needing charge and the alts feeding all the car/accs requirements as posible.

Which brings up a great subject.. Your Feed from Alternator and Grounds MUST be Equal to/or greater than the Alternator output. Which also means bigger better fuses/fusible links..

[Nacho-RT74]

Incorrect..

The fuses are designed to protect SAME circuits installed, which remains the same. Your Cigar lighter, Radio, Lights, are still requesting the same load, then the fuse must be the same, and wires can be the same.

As mentioned, the amperes are not pushed in by the source, but sucked out by the accesories, and they are still the same. Your baby gets the same hungry no matter how much food are. So the correction to your statement is on the same quote you posted.

Diff is when you begin to add accesories on circuits not designed to hold more load. That's a diff story

[Dino]

I could be wrong, but I think Derwud is talking about the charging system wiring. Use the same gauge wires from battery to relay, and to alternator, and fuse accordingly. I ran 6 gauge with the 90 amp and a 100 amp ANL fuse. With the 120 amp alternator I changed them out to 4 gauge wires and a 120 amp ANL fuse.

[Nacho-RT74]

Once again the same...

You won't speed up the battery charge more than the battery itself is able to get recharged just because the alt gets more load to offer.

A discharged battery is one device more which suck load to get fully recharged. But chemicals inside gets its own speed limit by its own process .

Amperes can't be pushed in, just requested.

True is that with thicker path less resistance to the system. But  that's another story.

And depending on your power distribution thicker paths could be unuseful on some sections.

100 or 120 amps fuse can be killer to the system. Can't be that high. It will take a HIGH LOAD to get burnt in case of a short, and at that time the damage will be bigger where the short happened. Better protection will be reached with a lower fuse rate.


Once again, don't think a 120 amps power plant will source that. The battery on car is/was 500, 600, 700 amps reserve load ( maybe 100 to 130 cranking amps) and the fuse link is 16 gauge (rated to hold maybe 50 amps before blow) and it sourced all the car.

[Kern Dog]

I was reading about Lithium batteries last night.



The weight reduction is amazing. A group 24 I tested weighed 7 lbs versus this:



The new generation of Lithium Titanate batteries are MUCH safer than any that have been made before.
Another thing that is interesting about them is that their cranking power holds pretty steady even while it is being discharged. In other words, it will crank fast most of the time, it will only slow down just before it shuts down from excessive voltage drop. This is in stark contrast to regular lead-acid batteries that get slower and slower until they won't crank at all.

[timmycharger]

I was reading about Lithium batteries last night.



The weight reduction is amazing. A group 24 I tested weighed 7 lbs versus this:



The new generation of Lithium Titanate batteries are MUCH safer than any that have been made before.
Another thing that is interesting about them is that their cranking power holds pretty steady even while it is being discharged. In other words, it will crank fast most of the time, it will only slow down just before it shuts down from excessive voltage drop. This is in stark contrast to regular lead-acid batteries that get slower and slower until they won't crank at all.

no argument on the weight savings, that is very impressive.  What you described is exactly what I saw years ago in the hobby industry when switching from NICD/NIMH batteries that will discharge slowly until dead vs the lithium batteries that are more powerful and give power up until the end before completely quitting.  Same goes for drills/impact drivers.

What does make me nervous about a lithium battery in my car would be what happens to lithium RC car batteries when charged incorrectly, not balanced or used when damaged. They go up in flames quite often. Most RC guys use a charging bag for lithium batteries that contain any fire.

I was reading about lithium RC batteries just today.

https://www.boston.com/news/local-news/2025/01/09/onset-fire-lithium-ion-batteries/?p1=hp_featurestack

[Kern Dog]

Again, Lithium titanate is not the same as Lithium Ion.
I saw a video demonstration of the testing of the various car batteries for their responses to damage. The Titanate was no more likely to catch fire than a traditional lead-acid battery.

[timmycharger]

Again, Lithium titanate is not the same as Lithium Ion.
I saw a video demonstration of the testing of the various car batteries for their responses to damage. The Titanate was no more likely to catch fire than a traditional lead-acid battery.

Learn something new every day! thanks KD