The truth about "idle"
What should I ask when purchasing a new alternator?
Purchasing an alternator can be a very trivial and mind-numbing experience if you don't know what to look for or the important
questions that should be asked. It is for this reason that we are providing the following information, so the next time you have to make
a purchasing decision for a new alternator, rest assured knowing that you won't be left in the dark.
The first, and probably the most important thing to make note of is to be very cautious if you will be making your purchasing decision
by "price-shopping". Buying the least expensive alternator can - and usually will - cost you much more than you would have ever
imagined spending in the long run. Now that we have that out of the way, there are three important questions that you should ask
when buying a new alternator. These questions are not to be taken lightly because they can mean the difference between a long and
fulfilled life-span or the quick and painful death of your vehicle's electrical system.
The first question you want to ask when buying your new alternator is: What is the alternator's idle speed output? Nine times out
of ten, the most important thing to consider is alternator amperage output at engine idle speeds. This is because today's modern
vehicles come with extremely high electrical demands, to the point that many vehicles need nearly one hundred amps at idle just to
power the vehicle's computers and accessories, and this doesn't even factor in consumer added demands such as extra lighting, car
audio components, or off-road equipment. Additionally, when you starve your vehicle of the essential power it needs, it can quickly
lead to serious problems including poor engine idling, stalling, dimming lights, and even the most dangerous one of all - computers
and modules that power off when the voltage falls to low.
The second question you'll want to ask the manufacturer or reseller is: What idle speed are you basing your idle output
amperage on? What we are looking for here is the number revolutions per minute (RPM) of the alternator pulley when the vehicle is
idling. For many years, the industry standard was 2400 RPM, and there was a time when this was accurate. However, with today's
modern vehicles, idle speeds are typically between 1600 and 1900 RPM. Despite this fact, you will find that some companies are still
using the inflated idle speed of the past when calculating their amperage output ratings in an effort to advertise the alternator as a
"high output" unit. This is not only unfair to the consumer; it also creates a very dangerous situation for the vehicles electrical system.
Lastly, the third question to ask is: How did you determine the pulley speed at engine idle? The importance of this question is
largely based on the answer you receive to the first two questions. We are not able to speak for other manufacturers, and how they
get their numbers, but at Nations, we use the following formula: test, measure, analyze, then test, measure and analyze again, and
then confirm the results by testing, measuring, and analyzing yet again. We perform extensive on-car load testing to our alternators to
make absolutely certain that our alternators will deliver what we claim and have conducted extensive bench testing to every single one
of the alternators that we offer, and we don't stop until we get it right! When installed properly, more amperage will not hurt your
vehicles electrical system, but not having enough certainly can!
|How Supply and Demand Works in Your Electrical System
A common concern among first-time purchasers of high-output alternators is: "Will a high output alternator damage my electrical
system?" The answer is no, thanks to the concept of Supply and Demand. Alternators don't always make their full rated output, they
only charge as much as necessary at any given time to meet the vehicle's electrical needs. If you were to purchase and install a 250
amp alternator, that does not mean that it is always producing that level of output. There are two reason for this: 1. Most alternators
are only rated at max output leaving the consumer unaware of what the output is during normal driving conditions, and particularly at
idle. 2. Your vehicle may not require your alternator's max output. It will only consume what it requires. For example, if it only needs 50
amps at a given time, that is all that will be produced. It's much better to have it and not need it, than to need it and not have it!
Lets take a look at the following situation - Your original alternator has a rating of 120 amps with 80 amps at 1700 alternator RPM. This
was fine when your car was bone stock and didn't have any extra goodies, but then came the cell phone charger, the kids' portable
DVD player, those ultra-bright fog lamps, and not to mention the twelve-inch woofers and that gazillion-watt power amp in the back.
Now you've effectively created a power famine within the electrical system of your car. Obviously, your stock alternator is no longer
efficient at keeping your vehicle adequately supplied with enough power to run and protect your electrical components. Furthermore,
you might be surprised to find that In this scenario, it is not the added equipment that takes the punishment, but rather the very
important - and not to mention expensive - onboard computer and electronic system.
At this point you may be wondering how this affects your car's daily driving. Say for example, that you are cruising down the highway at
70 and your vehicle is looking for a constant 115 amps to keep all the electrical components working properly and functioning
smoothly. You are not experiencing any problems or power shortages, because your alternator is rated at 120 amps. However, to keep
up with the demand, it is working at almost maximum capacity, which is hard on the alternator, and significantly reduces its life span.
This will eventually cause premature failure. It might be more noticeable when driving around town in stop and go traffic or idling at a
stop light though. In this case, your alternator is not supplying your car with 115 amps like it needs, so you may notice such things as
poor engine idling, stalling, dimming lights, or even the entire onboard computer powering off.
The only answer is to give your vehicle the power that it needs, when it needs it. You have different options when it comes to solving
your power needs , but we at Nations Alternator know there is only one solution. Purchase and install a new high output alternator or
add a second alternator to your vehicle's stock charging system. This will ensure that your vehicle has the proper power it deserves at
both idle and high speeds.
|Is Your Vehicle Getting the Power it Needs?
There are a few different options available when it comes making a decision about supplying your vehicle with the power that it
requires to function properly and meet the demands of added electronic equipment. While we will be explaining the different options
available, we at DC Power engineering only view one of them as power solution. That is option number three, we put it last so that you
have the chance to hear all sides so that you can make the most informed and educated decision possible.
Option one is to do nothing and ignore the problem. The upside - None. The downside - You may experience all or some of the
symptoms listed above. Your alternator fails prematurely due to being over worked. The worst case scenario is that your onboard
computer system fails because it looses its source of power abruptly. If you are driving and your alternator is not charging your
battery, essentially your vehicle is using only the juice in the battery to keep it self running. Once it is gone your vehicle shuts down
immediately with no warning, including your vehicles computer system. Think about all the electronics in your house, primarily your
home computer system, now imagine that the power company comes along and shuts off the power to your house at the main breaker.
When that power comes back on they recommend that all electronic equipment and computers are disconnected from the wall
because the sudden surge of power coming back into the house has the ability short them out. Now, back to the example your car or
truck, the same thing happens when the battery is reconnected or you try to jump start your dead battery. This is a very dangerous
Option two is to have the alternator rewound to have adequate rating for your needs. The upside - You have found someone to rewind
your alternator and claims that it is rated at 200 amps and 150 amps at idle, or whatever works for the needs of your vehicle. This is a
good solution as long as you ask the following question, "What idle speed are you basing your idle output amperage on?" The
downside - The answer to the questions just asked is generally 2400 RPM. If at idle you alternator is spinning at 2400 RPM this is
good news for you, but most modern vehicles that speed is more commonly between 1600 - 1900 RPM. So if your alternator's "true
idle speed" [link to truth about idle article] is 1700 RPM chances are during idle your alternator is only producing 40 or 50 amps or
even worse, not charging at all! Now you would have a serious problem because that is probably not even enough to maintain your
vehicles most basic charging system needs and you are at big risk of serious problems! And, if you are only having your alternator
rewound, they could still be re-using the other used components which have also experienced the wear and tear of working too hard,
which can cause the rewound alternator to not perform as well or last as long as expected and those parts might not have a warranty.
Option three is to purchase a new alternator or add a second alternator [link to running two alternators article] to your charging
system. This is the only option that we view as a real solution to repair the needs of your charging system. The upside - All extra and
standard vehicle equipped electronic components will have enough power to function properly and safely. And as an added bonus
your electronic equipment will not fail prematurely due to power shortages which means saving big bucks. The downside - A little larger
investment upfront. Buying a high quality high output alternator will cost you more than option one or two but is worth every dime in the
For more free information fill out our request form, e-mail, or call (573) 334-2632 to speak with a friendly and knowledge professional
available to answer all of your alternator questions.
Back to High Amp Alternator
|Quality Starter, Alternator
& Electrical parts Service
& Distribution Since 1930
Hours 8-5 Central Time Mon-Fri
"Do You Really Want To Start Something"
|Quality Starter, Alternator
& Electrical parts Service
& Distribution Since 1930