Risks of Running High Amp Alternator?

-

jrcr_15

Well-Known Member
Joined
Jan 3, 2006
Messages
125
Reaction score
36
Hi there,

I hope everyone is doing great and keeping safe in these odd times.

Question about upgrading your alternator to one with a higher output. I am aware that when upgrading to an alternator with a higher output, you are required to upgrade the main wire coming off the alternator through the bulkhead/fire wall and into the main weld/splice behind the gauge cluster. Using the appropriate gauge as per the amount of output from the alternator.

I did this awhile back and fixed my problem.. at the time.

However, I have made more performance upgrades and added in more electronics and as such I need to go bigger again as my car very slowly drains the batteries when running / driving.

I am in the process of calculating how much my total system needs and was thinking of adding another 25-40% on top of that for safe measure / potential future expansion, as I do not want to do this again.

I expect the final number to be quite high. Here are a few items I have as an example:

Spal Cooling Fan x 2
Cooling Fan Controller
Electric Water Pump - High output
Fitech Fuel Pump x 2
Fitech Unit
MSD 6AL Ignition
Snow Water-Meth System

I am not an electrical expert and want to be careful not to BBQ my car.

If going to a high output alternator, like 140A / 160A etc, do I run the risk of burning out other components? Like my voltage regulator etc? Are there other items I should be looking as aside from the main weld/splice?


I have been reading into a lot of people going the Denso route and that may be the direction I head in..


Any insight would be much appreciated.


Thanks
 
I sure wouldn’t run through the bulkhead connectors with anything more than a stock electrical system. Those connectors are barely adequate for that.
 
IMHO

I would take all those electrical loads and run them to a dedicated distribution / fuse block directly off the battery. then run whatever Alternator you want with the output of the Alt going directly to the battery / distribution / fuse block. the rest of the car, under dash, lights etc can run off of the battery / alternator as it does now.

let's say the car without all the extra electrical loads pulls 10-20 amps with headlights, brake lights etc on. and your add on electronics draws 100 Amps. your 150A alternator can supply all of it and charge the battery too. If on the other hand you tap all the extra electronics onto the existing wiring in the car your set to roast marshmallows
 
Yes I agree with Mike. I would bypass the bulkhead completely with a larger sized wire (with appropriate current handling capacity) from the alternator directly to the battery and put in a Voltage gauge inside the car.
 
I have a lot of electrical load in my car as well, I have a 120amp Chevy style 1 wire alternator with an 8ga wire going straight to the battery. I bypassed the factory ammeter by splicing the wires together. I also removed the black factory wire from the bulkhead connector in the firewall that originally went to the alternator, and then I removed the main power wire pins from the bulkhead, drilled out the hole where they were, and ran a new main power wire directly through the bulkhead. I left some extra slack in it in case I ever need to remove it.
The upper circle is where I cut it from the dash harness, the lower circle is what goes directly through a drilled out hole in the bulkhead. They are the same wire, they look different because part is shrink wrapped.
The reason you want to drill a hole and remove the connector pins is because they are super thin and will melt with lots of amps
08A1DC78-0440-4BF3-88BC-C772B4239704.jpeg


FD6CB352-3680-4523-B919-D90B4073921E.jpeg
 
Most alternators don't put out a lot of amperage at idle including the Denso and after market rewound Mopar style ones. You definitely want to run any increased load to an under hood distribution point with proper fusing and relays.

I upgraded to a rewound CS 144 with a dual heavy duty bridge rectifier. It puts out over 140 amps at idle and over 200 amps at a fast idle. It bolted right on with a simple bracket although I did have to adjust my belt path slightly.

Here's a picture of the alternator mounted above my A/C compressor on the RB in my '70. The same shop sells the adapter bracket.

High Output Dual Rectifier High Durability Alternators

IMG_2602.JPG
 
If you ain't done the MAD bypass yet, you need to do that and THEN SOME. That's a lot of current you're gonna need on multiple circuits.
 
The problem is not only the bulkhead connector terminals, but the ammeter itself

One of my favorite examples is an electric furnace and the internal interconnecting wiring. These almost universally use 1/4" flag push on terminals.......the very same type terminal used in the bulkhead connector. Electric furnace elements are pretty much standard at 5000 watts per element. At 220V that is 5000/220=23amp nominal. So every single flag terminal in that furnace has to put up with about 20-25amps, AND THEY FAIL OCCASIONALLY

So if those fail with no more than 20A current, imagine when you double, triple, or quadruple that current

furnace-breakers.jpg
 
Last edited:
Since you are trying to make a 50 year old electrical system work with 21 Century loads, I would bite the bullet and upgrade the whole harness. You can then make allowances for any more future changes you might make and all wiring, connectors etc. will be made from modern materials and fresh insulation. Cost less than an electrical melt down...
 
Thanks everyone for the input. Sorry I should have mentioned this in my original post, I have already eliminated the Amp Meter and replaced it with an autometer voltage gauge. I have also bypassed the bulkhead connector completely.

Would this just be a matter of upgrading this to accommodate the increase power?
 
The only upgrade you really need is to have the appropriate mounting rigidity for the alternator, large enough wire between the battery and alternator output, with appropriate fuse/ breaker protection. And make certain that the VR (if external) is actually sensing right at battery voltage so it won't over charge

And of course the ground path also needs to be in good shape. On many systems this is already taken care of because the alternator is grounded to the engine, and the engine grounded by the main cable to the battery. BUT SOME modern alternators have a separate ground connection. So in that case, make sure it's in good shape and large enough

Yet another issue is whether or not you are using a "one wire" because those sense battery voltage through the charge/ output wire. This means that wire must be MUCH larger so that there is no voltage drop.
 
The only upgrade you really need is to have the appropriate mounting rigidity for the alternator, large enough wire between the battery and alternator output, with appropriate fuse/ breaker protection. And make certain that the VR (if external) is actually sensing right at battery voltage so it won't over charge

And of course the ground path also needs to be in good shape. On many systems this is already taken care of because the alternator is grounded to the engine, and the engine grounded by the main cable to the battery. BUT SOME modern alternators have a separate ground connection. So in that case, make sure it's in good shape and large enough

Yet another issue is whether or not you are using a "one wire" because those sense battery voltage through the charge/ output wire. This means that wire must be MUCH larger so that there is no voltage drop.

Good info here. My CS 144 senses voltage from the battery in the trunk.

Also, I replaced all my interior lights with LED's, so the cabin amp draw is very low. I also had my amp gauge swapped to a volt meter.

All the other high amp draw electrical loads are fed through relays and fuses through my underhood distribution block except my fuel pump which is fed from the trunk from the battery via a pair of 40 amp relays that are key switched triggered.
 
Again, really appreciate the information posted here.

I have been looking into this further and found some pretty decent Powermaster alternators that may meet my cars needs. I am seeing that most of the higher amperage ones are internally regulated, and from what I understand are the single wire style.

Example:
Powermaster Street Alternator

Currently I am running a 2 wire Squareback, externally regulated with my voltage regulator mounted on my firewall.

If I made the switch, how would this be wired? I am assuming I take my existing VR out and the new alternator would take care of all that?

Again, just being cautious to not burn up my car!
 
Again, really appreciate the information posted here.

I have been looking into this further and found some pretty decent Powermaster alternators that may meet my cars needs. I am seeing that most of the higher amperage ones are internally regulated, and from what I understand are the single wire style.

Example:
Powermaster Street Alternator

Currently I am running a 2 wire Squareback, externally regulated with my voltage regulator mounted on my firewall.

If I made the switch, how would this be wired? I am assuming I take my existing VR out and the new alternator would take care of all that?

Again, just being cautious to not burn up my car!
You would just remove everything that connects to the VR and run an 8 gauge wire to the battery/starter relay.
Also, just from my personal experience, I would go with a Tuff Stuff alternator instead of a Powermaster. I had to send my powermaster in for repairs 5 times within 100 miles and it’s still trash. I’ve made a couple threads explaining everything about it.
You can have my one wire 95amp powermaster if you want it. I was planning on using it for target practice
 
Thanks everyone for the input. Sorry I should have mentioned this in my original post, I have already eliminated the Amp Meter and replaced it with an autometer voltage gauge. I have also bypassed the bulkhead connector completely.

Would this just be a matter of upgrading this to accommodate the increase power?

Yeah that couldda saved a little time.
 
If you ain't done the MAD bypass yet, you need to do that and THEN SOME. That's a lot of current you're gonna need on multiple circuits.
What would you recommend on top of the MAD bypass?
 
What would you recommend on top of the MAD bypass?

MAD has some really good ideas including the famous Bypass. They also wisely recommend running a distribution point that is fed directly from the alternator. All moderate to high amp draws should also terminate there.

Using quality relays, fusing and wiring is critical. I've found Marine Supply stores carry higher quality components like these in addition to fuse blocks etc. Auto stereo fuses and circuit breakers are large enough to handle hundreds of amps, and I use those sized to my needs.

I also use dedicated grounds to match the positive cables from my alternator, starter, battery in trunk and engine block. power flows equally through both positive and negative. I like the welding supply houses cabling and end fittings, because of its tough casing and super flexible fine strand cables.
 
The 1963 and 1965 Mopars have dedicated buss-bar feed-thrus in the bulkhead for the thick ALT (blk) and BAT (red) wires, unlike the "56 terminals" (spade) of other years which melt. Still, I wouldn't send >70 A thru the dash ammeter since any corrosion at the screw connectors could overheat, plus the ammeter isn't ranged for that. As stated, you can just run the ALT output straight to BAT+ in the engine bay. The 5.2/5.9L Magnum engines do that, running across the top of the timing cover.

I did that, using a Magnum ALT/BAT harness. But, I installed back-back 200A diodes in that path so the normal path is thru the ammeter until >0.3 V drop in that path causes the diodes to start shunting current directly to the battery. That keeps my ammeter active. Search my post "Modernized Wiring ...". But for most people, just live with a dead ammeter as all modern cars do. You can use a cigarette lighter voltmeter to monitor while driving, as I do in my modern cars. If you see >14 V, the alternator is outputting fine, so no surprises at the next stop. Someday, when the cluster is out, you can install a voltmeter in place of the ammeter.
 
The 1963 and 1965 Mopars have dedicated buss-bar feed-thrus in the bulkhead for the thick ALT (blk) and BAT (red) wires, .

Whenever someone starts preachin' to me about "how smart" the engineers were that designed something, or that they "built it that way for a reason" I think of stuff like THIS. They KNEW the answer, and partially solved it with the police/taxi/ fleet wiring modification
 
Whenever someone starts preachin' to me about "how smart" the engineers were that designed something, or that they "built it that way for a reason" I think of stuff like THIS. They KNEW the answer, and partially solved it with the police/taxi/ fleet wiring modification

The biggest part of the problem is usually with the bean counters who won’t pay to do it right. A Lot of the time the technical decisions turn into budget decisions.
 
What would you recommend on top of the MAD bypass?

Adding some sort of protection coming out of the alternator hot. Like a mega fuse. A big one. @67Dart273 can give you a better idea, I imagine. I am not an electrical genius. I know just enough to get by.........and then get in trouble. I haven't burned anything up though.......yet.
 
Most alternators don't put out a lot of amperage at idle including the Denso and after market rewound Mopar style ones. You definitely want to run any increased load to an under hood distribution point with proper fusing and relays.

I upgraded to a rewound CS 144 with a dual heavy duty bridge rectifier. It puts out over 140 amps at idle and over 200 amps at a fast idle. It bolted right on with a simple bracket although I did have to adjust my belt path slightly.

Here's a picture of the alternator mounted above my A/C compressor on the RB in my '70. The same shop sells the adapter bracket.

High Output Dual Rectifier High Durability Alternators

View attachment 1715630108
Thank you - This is very helpful information. What size fuse are you using for your alternator? Also what about your fusible link?
 
Overcomplicated......I don't use the amp gauge at all and have no need for a voltage gauge either. I agree with doing away with the bulkhead connector as most of them are half fried and burnt up by now anyways. Get a 1 wire alternator from Jones Racing as they have very high charging output at idle. Utilize a completely different and new fuse/relay box and do away with the factory setup, I run a Leash Electronics in one car and have a system from Race Wire Solutions for another one. I have the battery in the right rear, and utilized most of what member Crackedback illustrated for the starter relay, alternator charging and battery disconnect setup. I run a 4 gauge welding cable from the battery up to the alternator with a high amp electrical pass through for the firewall down low on the passenger side.
 
-
Back
Top