In many classics and musclecars, the output of the alternator was simply to sustain the power needed to run the engine with the headlights on. There wasn’t any need for high-amp alternators, because the only accessory that many of these cars had were an additional pair of speakers in the back. The addition of fog lights, driving lights, amplifiers, and other high powered accessories hadn’t really hit the market very heavily until the 1980s.
Some cars also have an air suspension system, meaning the compressor needs to keep that air tank full – and that draws on the electrical system more than ever was intended. Upgrades to digital ignition boxes and alarm systems also add to the amount of wiring that is added to a vehicle; people are also adding electric cooling fans to replace the mechanical fan. All of these components are going to require a better charging system if you don’t want to overwork your battery.
So how do you upgrade an electrical system that was never designed for all of these accessories? With many older alternators, the wiring alone can’t handle more than the 45-60 amps the factory alternators were putting out, and the voltage regulators were mounted remotely, so adding a high output alternator meant a lot of rewiring and upgrading the existing wires to handle more current. Many factory alternators from the classic car era had 14-16 gauge wires, which are not sufficient to handle higher alternator outputs.
One solution to the charging dilemma is to upgrade to a single-wire alternator that puts the power directly to the battery – and only when the engine is running. These alternators, like the one’s we’re covering here from Power Master and Tuff Stuff are internally regulated, so the power wire doesn’t need to pass through a factory voltage regulator, through the dash wiring, or through any existing harnesses. Being a true one-wire alternator means that having a solid ground and an ample wire attached to the battery is all that you’ll need to keep that battery charged, and will do so with 100 amps output or more.
What Determines The Output?
For many people, the term “bigger is better” isn’t just a saying; some people think that going big is always better, no matter what you’re talking about. However, unless you’re powering a huge audio system, have air compressors, video monitors, and lots of additional lighting on your show car, you don’t really need to get the biggest and most powerful alternator.
We checked out Powermaster Performance and Tuff Stuff Performance to get a better idea of how to choose a one-wire alternator, and to learn more about them. Both companies have guides for how to determine what amperage you should consider when upgrading to a one-wire alternator, and they’ll be the first to tell you that if you’re just running the most basic of electronics in your car, you don’t need a huge-output alternator.
While running a 200-amp alternator isn’t going to overcharge a battery, it’s the equivalent to installing a larger fuel tank: the capacity increases, but you’re still using the same amount of fuel when you drive. Likewise, high output alternators aren’t going to improve the quality of electrical components because they consume the power they need and nothing more. They will improve their effectiveness when the alternator is installed correctly, but when a 100-amp alternator will suffice, 200 amps will do very little other than empty your wallet more.
Powermaster has technical bulletins that can help you determine the average amperage load of the accessories in your car, such as air conditioning, auxiliary lighting, high-powered stereos, etc.
Tuff Stuff also has a technical bulletin for installing a one-wire alternator and how to choose wire gauge. These are the bulletins that will apply to most people with regular drivers.
If you’ve been to an auto stereo competition where people are running thousands of watts and multiple amplifiers, it’s common to see someone with multiple alternators powering their electrical system. As you can guess, these are show vehicles and aren’t typically driven on a daily basis, and there’s a purpose to it. Neither Powermaster nor Tuff Stuff recommend multiple alternators for a daily-driven vehicle – leave that to the show cars.
If you do some research on one-wire alternators, you’ll find pros and cons, like almost anything performance oriented. Brady Basner, Technical/Marketing Director for Powermaster, says, “Most information found online is either outdated, doesn’t apply to all one-wire alternators, or it’s simply incorrect.”
Most information found online is either outdated, doesn’t apply to all one-wire alternators, or it’s simply incorrect. -Brady Basner
When one-wire alternators first came out, those were valid concerns: low output at idle meant sitting at a light with headlights and stereo blasting wasn’t good for the electrical system or the battery. Some alternators required revving the engine to a certain RPM in order to excite the alternator so it would turn on and start charging.
Bud Riser, Technical/Marketing Rep for Tuff Stuff, said, “All Tuff Stuff alternators charge at very low engine RPMs.” Riser stated that it doesn’t take revving the engine to get the alternator to start charging, and that the alternator will put out sufficient amperage at idle.
He said, “There is no need to worry about using an underdrive pulley, or an ignition regulator turn-on with Tuff Stuff units.”
While some of the concerns were valid many years ago, they aren’t a concern with the alternators that both of these companies produce, all of those concerns were taken into consideration to produce one-wire alternators that would perform at idle/low RPM, and not cause concern for modern one-wire alternators.
Another concern was the lack of an external voltage sense connection. Again, this is something most manufacturers have stopped doing a long time ago. What was happening was that a wire was sent to a remote location on the car and it would send a signal back to the alternator reporting what the end voltage was.
If the voltage was lower, then it essentially told the alternator to produce more voltage. Riser said, “The problem with this setup is with concern to the initial voltage drop. If there’s a voltage drop across a wire that means the problem is with the wire; the size of the wire or the connection is bad. More current should not be pushed through a wire with a problem.”
Simple, One-Wire Hook Up
As you might assume, the concept behind a one-wire alternator is that there is a single wire used to connect the alternator to the battery. The voltage regulator is internal, and there are no other wires that need to be connected to your electrical system. However, that doesn’t mean that you don’t need to have a solid ground wire connecting the alternator to the engine/chassis.
With many of these alternators, they are chrome or powdercoated, and that can compromise a good ground connection. You should never assume that the mounting bolts provide a clean ground, and therefore, a second ground wire should be used to provide a ground connection for the alternator. That wire should be of similar gauge as your hot wire to the battery connection, and it needs to be mounted to the engine block, which should also have a good connection to the chassis. Without a solid ground connection, the alternator may not charge properly.
While these two connections aren’t complicated, they are required and care needs to be taken that the wires used are of the proper gauge, and that they are routed away from moving parts and areas of higher temperatures – like headers and exhaust.
The beauty of this is that it eliminates those extra, messy wires going to the external voltage regulator. – Bud Riser
Riser said, “One wire alternators are pretty straightforward regarding installation. All the car owner needs to do is connect the positive post on the back of the alternator to the positive post on the starter solenoid or the battery. There is no other wiring required for the alternator to work.”
He added, “The beauty of this is that it eliminates those extra, messy wires going to the external voltage regulator.” He recommends that the wires be removed, or taped off, and hidden away from view. But if you do have a dash light that you want operable, they can tell you how to connect it, based on your particular vehicle.
Running a longer wire back to the battery will require a larger gauge. This is because there is an inherent amount of resistance with longer wiring, and that resistance produces a slight voltage loss. You might remember something called Ohm’s Law, where anytime the resistance is increased, the amperage, or current, is decreased for a specific voltage.
For remote batteries, it’s best to run the alternator wire to the battery, being sure that proper circuit protection is utilized. This can be a large circuit breaker or fuse, but it must handle constant amperage that is higher than the alternator’s output. The charge wire can be run to the starter solenoid, providing it’s connected to a large gauge wire that runs to the battery.
Below is a chart with the recommended wire gauge for your one-wire alternator. On the left, a standard guide for wiring the alternator with the battery close by; on the right is a guide for remote mounted batteries. As you can see, the further the distance, the bigger the wire should be.
One-wire alternators aren’t necessarily “better” than typical alternators of similar quality, the big benefit is the ease of installation. When you’re building a car and have to start from scratch with your electrical wiring, the one-wire alternator will save you a lot of hassle – and help to keep the engine compartment tidy. For restorations, most people tend to stick with what the factory offered, and both Tuff Stuff and Powermaster can help with those applications as well.
But for simplicity, when you’re running accessories and additional components and you don’t want to deal with upgrading all of your wiring, the one-wire alternator removes all doubt about the small, factory wiring that was designed to carry the current load of your original, wimpy 45-amp alternator.
To find out what applications and alternators are available from Tuff Stuff Performance or Powermaster Performance, check out their respective websites and contact them if you have any questions – they’d be glad to help get your car wired for performance charging. And be sure to get the proper size wiring for your application beforehand – you should never use wiring less than what is recommended in the guides above.