High Powered Alternators

[MattVAS]

No reason to high-jack a previous thread.
Very recently Classic Motorsports did a wonderful article about alternators and the issues with over doing it.

Here is the link please enjoy the read
https://classicmotorsports.com/articles ... lternator/

[aj81spider]

I'm sympathetic to your desire to make sure people understand that they generally don't need the excess capacity of a higher output alternator. However this article irritated me (to the point that I have to respond) with the alarmist tone when it called installing a higher capacity alternator "dangerous."

Their statement

"Think about this: If you install a modern, 80-amp alternator and use the stock wiring that was designed for a 36-amp alternator, what’s the inevitable outcome?"

is so deeply flawed as to make me wonder as to the electrical competence of the author. The vast majority of the wiring in a car is not designed for any more than 8-16 amps and is fused accordingly. There is a very small proportion of wiring that isn't fused. The capacity of the alternator is completely irrelevant to a fused circuit. For the most part the wiring that isn't fused will get overloaded by 65 amps as easily as 90 amps. 4-6 core wire needs to be 3 AWG to have a capacity of 65 amps (reference https://www.engineeringtoolbox.com/wire ... d_419.html if you're interested). I'm not aware of any wiring in a Fiat that's 3 AWG. You can get better than 65 amp capacity out of single stranded wire at 8 AWG - good luck working with single stranded 8 AWG wire.

The argument that buying an alternator for additional capacity in a stock Fiat won't solve any electrical problems is a good one. The argument that it's a bad idea or "dangerous" to install such an alternator is simply wrong. If you want to use a higher capacity alternator there is little problem with that, and if you add significant loads to the car (like seat warmers or a high output stereo) there are some benefits.

[chrisg]

What was it, Ohm’s law. I learned that stuff a long time ago.

[AndyVAS]

A.J. - Perhaps you're looking at home wiring (110v/220v) and not automotive 12v. In a 12 volt system you can run 100amps through a multi-wire 6ga. In a 110v home circuit you would need 3ga copper single core.

Sure, the article seems to over sell how you'll burn things out but that isn't as much a stretch as it seems at first glance. Keep in mind that most people do NOT replace any wiring at all and that hobby cars sit around. Take a battery with low charge and a 12ga wire from a 100amp alternator. In that case the alternator is likely to over power the wire and cook the insulation off it pretty quick. Any wires running with it will also melt and presto, a big short! As for the rest of the system, old cars, such as the 124, don't fuse all the circuits and don't use fusible links.

[DieselSpider]

With so many with the battery in the trunk such as my 1978 that's an extremely long wire connected directly to the alternator with no fuseable link to protect things that could get hot running under the carpet under the side of the drivers seat, across under the rear seat/parcel shelf and way too close to fuel lines.

Electrical system failures according to forensic/insurance investigators are the second most common cause of car fires with excess hydrogen from overcharging batteries being a major factor. Hot wires from cooking a discharged battery that is off gassing hydrogen can get very intense which are an explosive combination. I had this happen in my F53 which since it was computer controlled started to buck and misfire every time it got over 5 mph and high charge started to kick in since voltage was too low to keep the ECU going once the battery started to short internally at high charge however if it had been an older vehicle without the ECU to act up or a fuseable link it would more likely had just gone on until the battery exploded or the cable overheated and shorted to ground or started burning. The hot wire on the battery was indeed way to warm for my comfort level when I pulled over to check what was happening getting to it before a link or wire had burned and that was on a modern high amperage system with all the protections.

Its not the big far fetched uncommon flight of fancy that many would prefer to believe it is.

[aj81spider]

Take a battery with low charge and a 12ga wire from a 100amp alternator. In that case the alternator is likely to over power the wire and cook the insulation off it pretty quick.

That is true with either a 65 amp alternator or a 95 amp alternator.

You're right about 100 amps through 6 AWG (for runs of less than 10 feet). Here's a link to automotive wiring that adds distance to the AWG consideration http://www.offroaders.com/technical/12- ... e-to-amps/. However that doesn't negate my point. Most of the wiring in a Fiat cannot see either 65 or 95 amps because it's fused. Those unfused circuits that can see more current will be overwhelmed by either alternator, especially when supplemented by the battery current (see below).

With so many with the battery in the trunk such as my 1978 that's an extremely long wire connected directly to the alternator with no fuseable link to protect things that could get hot running under the carpet under the side of the drivers seat, across under the rear seat/parcel shelf and way too close to fuel lines.

If you short that wire out with either the 65 or 95 amp alternator it's going to cause problems. Worse, if that wire shorts the battery is a bigger problem than the alternator, as it can put out hundreds of amps, and will likely catch fire or explode as it pumps those amps into the short. In fact, any consideration of the alternator output has to consider that the battery will be boosting the current as soon as the voltage from the alternator drops (which it will as soon as it gets close to it's max capacity). Your unfused wiring is in danger whether the alternator puts out 65, 95 or 0 amps. That is why you need to disconnect the battery before working on the electricals of your car.

I'm not saying that electrical problems cannot be serious. I'm not saying that shorts won't burn wires out. I appreciate that you are educating the community on the fact that extra current from the alternator isn't really a benefit (unless you are increasing the loads in your car). However I think that message is weakened by claiming extra "danger" and people who might be willing to pay for the 95 amp alternator for other reasons (like it's new and not remanufactured) will be scared away for no good reason.

I stand by my opinion that there is no appreciable difference in "danger" between a 65 amp alternator and a 95 amp alternator.

[DieselSpider]

When there is a battery issue you could be getting to critical much faster with the higher amperage alternator. As mentioned by insurance investigators, they see more issues from failing batteries drawing high charge rates overheating wiring which they put as the #2 cause of car fires. With the extremely long battery cables on the rear mounted batteries there is not as much extra capacity to deal with both the line length and almost 50% greater amperage. Batteries commonly fail and draw high so issues from a failing battery would be the larger problem to me.

[spider2081]

Here we go again with alternator opinions So I might as well post mine.

I think the Classicmotorsport article has lots of merit. Especially when discussing the physical mounting of the alternator. I have seen a number of aftermarket alternator conversions where the belts slip because of poor mounting and pulley compatibility. Undersized bolts allowing the alternator to vibrate within the mount etc.
Not mentioned in the article is a point I think is important. The Fiat alternators voltage regulators were set for a max output voltage of 13.7 volts. Most modern alternators are regulated at 14.5 volts or more. This makes for brighter lights faster wipers but also means higher current is passing through the original conductors. Yes the majority of the wires are fused and protected but still they are working harder. This also increases the risk of overcharging the cars battery. Overcharging a battery reduces its lifespan.
My experience is Fiat's choice of wire for the lead connecting the alternator output to the starter solenoid is marginal. I have seen many of them melted or over heated or crystallized. I think this wire should be replaced with a #6 wire. When the battery in trunk mounted the green battery cable is adequate. I have not seen one overheated or fail electrically. I have seen many with very poor installations of aftermarket battery cable ends.
I am not sure the current rating of the electrical terminals used in the unfused circuits have the current rating that the wires have so the terminals seem to overheat causing intermittent operation. In some cases the wires insulation melts close to a terminal. Increasing an alternators capacity can contribute to this issue.
Personally I think the Bosch 55/65 amp alternators with internal voltage regulators are very simple reliable. I have serviced around 20 of them and have yet to find a bad bearing. Using or keeping these alternators eliminates all the physical mounting issues.

[VAS]

Lest there be any confusion, our 65 amp alternator, part number 20-1365, is new, not remanufactured.

[DieselSpider]

Lest there be any confusion, our 65 amp alternator, part number 20-1365, is new, not remanufactured.

And costs less than many of the on-line rebuilts too.

I should note though that my local rebuilder does a really great job rebuilding alternators with internal regulators for well under $100 and that's with new bearings, brushes, regulator and diodes. If one doesn't have a really great local source your new one is a top contender.

[Yadkin]

Upgraded alternators are much better at steady output than old designs so I consider them almost mandatory. I use the wire table for chassis wiring (not house wiring) and up-size the wire to charge the battery, and the ground. I install a circuit breaker in this hot lead that doubles as a kill switch. I tee off the hot lead to power a new fuse panel and then use a new 40 amp fuse to back feed the original fuse panel.

I also like to move as many high amp circuits as I easily can from the old panel to the new one: cooling fan, headlights and horn. On old cars without relays to these components I put them in and use the old wiring to trigger the relays.

Some early 60's cars used an in-dash ammeter without a remote shunt. These are a big problem when upgrading the alternator. Not only does this put a high amp circuit (literally) on your lap it makes taking out the gauge cluster pure misery, often with bolt-on connections that you can't see or reach. I eliminate that circuit completely and convert the ammeter to a volt meter.