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Extreme Veteran
Posts: 524
Location: West Jordan | Tech info post questions if you have them. This is a basic rundown of the difference in the charging systems, every vehicle is different, go with what works for you but this may help you in your decision. Generators; basically a generator is creating power by a drive belt that is turning the armature inside a field coil. There are some things you can do to get better power out of it but for the most part it will not do over 50 amps with about 15 at an idle. Idle power is important because if you are pulling 30 amps at idle and your generator can only do 20 amps you are pulling power from the battery and the generator must replenish the power when you step on the gas, in effect it is always running behind. Most generators make power in DC which is another limitation factor in its output. Most generators use a cut-out switch or a regulator that controls the output of the generator. If you have a bone stock vehicle there is no real reason to convert to an alternator, if we are talking about 1950 or so and newer, older ones have limitations but can be swapped out for a newer style generator, however is has become cheaper to install a GM 10SI alternator. Alternators; it is really rather stupid that we call alternators generators, they are very different. The alternator is a direct descendent from the greatest scientific mind ever to exist, Mr. Tesla. It is basically a 3 phase AC power generating device with a rectifier bridge to convert the AC to DC. A rectifier bridge is a device the splits the AC wave, the basic design is 6 diodes, 3 negative and 3 positive. A diode is like a one way valve, it allows the positive part of the wave to go to battery positive and the negative of the wave to go to the negative. In the alternator a rotor spins inside a stator, the stator is the copper winding you can see through the vent slots on the side, the rotor attaches to the pulley. In order to make power the alternator needs to have a large rotor. The larger the rotor, the larger the mass and the more magnetic field it can generate, and the more field it generates the more power will flow in the stator. The rotor and stator must have a very tight air gap, the closer the rotor is to the stator the more power will flow in the stator. The metal in the rotor must be very high quality, hard to find today with all the reclaim metal mixed into the new metal. The lack of quality metal is one of the main reasons why your are probably better off with your factory generator, chances are It has an original armature that has been rebuilt and it has higher quality metal. All alternators have a regulator with a voltage set point, the regulator supplies power to the rotor coil inside the rotor and that creates an electromagnet and cause the power to flow in the stator. The regulator is either inside the alternator or outside on the fender. Mopar designers were way ahead on this and had a better understanding of the heat that alternators generate and that is why the alternator is more opened up like all alternators are today. If you have upgraded the air conditioning, added more power in the stereo, H4 bulbs in the headlights, and / or power windows you may want to consider an alternator. Alternators will produce 45 amps and go up from there, so you are going to need to run a larger cable from the alternator to the battery, and if you have an amp meter the cable to and from the amp meter will need to be upgraded, if you want to amp meter to work correctly. The main reason to use an alternator is for maximum power at lower RPM, some 90 amp alternators can do 75 amps at an idle must most are 35 to 50 depending on pulley sizes Alternators that look like generators; let me start by saying I don’t like them because I dong think you get much band for your buck, they are way over priced for what they are. It is an alternator, it has a rotor, stator, regulator, and rectifier. The problem is the rotor is too small to generate a strong field so power suffers. In our testing we have found very bad lower RPM performance. Yes they will do 90 amps but at about 7600 engine RPM, so you are buying power you really can’t use, but if you have lower power requirements to begin with then it may work for you. But again it is usually cheaper to rebuild your stock generator than buy an alternator that looks like a generator. The worst part is they don’t have very good idle power, some lower quality units are as lower as 15 amps, yup, lower than the stock generator. So that is a basic difference between the options, later is will do a testing and diagnose post. Post questions if you have them. Keep one thing in mind, alternators generate heat, if you run them at or near full power they will have a short life span, it is always better to have an alternator that can produce more power than you need. |
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Expert 5K+
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Location: Perth Australia | Good post Darren
I like to tell people that the basics of an alternator are a reverse of a generator as in, in a generator, the feild coils are stationary and the armature generates power by spinning (rotating) through the magnetic field the feilds produce, where as, in an alternator, the feild coil now rotates (rotor) and the armature is stationary (stator).
In a generator, there are a north and south magnetic pole (normally 2 screws visible from the outside, 180 deg apart), in an alternator, north and south are achieved by 2 1/2vs of the rotor (front and rear with "fingers that cross over the centre line of the feild)), so, as the rotor rotates, at any given point of the stator winding, it has an alternating north/south magnetic feild pass through it.
Just curious, are you going to go into AC theory?
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Expert
Posts: 4589
Location: Northern New Jersey | AC Theory.
Let me go look for my Slide Rule! |
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Extreme Veteran
Posts: 524
Location: West Jordan | Nope, just basic info, don’t think anyone wants to be electrical engineers, just some basic info about how the charging system works. |
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Expert
Posts: 1730
Location: Michigan | Darren,
In your eval of Alternators that look like the generators, did you evaluate this companies products? http://www.qualitypower.co/item.php?item_id=288 |
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Expert
Posts: 1906
Location: Ontario, Canada | Darren, thanks for the post. I have some comments and a question. Using my Regal Lancer as an example, it will idle at a traffic light with headlights, wipers and AC blower on high and only show a slight discharge. One generally only idles for a few minutes at a time so I always thought that one of the reasons we had a battery was to "take up the slack" in such cases. I should mention that my generator is a true 40 amp low cut-in model. When it was professionally rebuilt the rebuilder wanted the regulator as well. I understood that when they were bench testing the generator they would adjust the regulator to match. Is this true?
Greg |
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Extreme Veteran
Posts: 524
Location: West Jordan | @Beltran;
First of all, full disclosure, we are in competition with the company that charges you lots of money and then puts a big sticker on the side of the unit so you can advertise their product. We are not authorized to do testing by anyone, we buy them at list price, test time then take them apart to inspect the internals. We have tested ones from $200 to almost $1000. We did test that unit but for getting sued reasons I am not going to get into specific info, the test we did was to determine if this was a good idea for us to get into. Two things I can say about it is this, for the most part, the more expensive the unit was the better it performed, and the higher the quality. The real problem with this design is cooling, they will run hotter because of the design, and heat destroys alternators, but how much effect it will have depends on your local temps, how you drive it, when you drive it, and accessories. So I will put it this way, if my choice was the one in the link or an alternator, I would pick an alternator, I would get the same if not better long term performance at about ½ the money, but keep in mind I am not a purest, the fact is this, if Chrysler would have has the technology of an alternator in 55, your car would have had one on it from the factory.
@LD3 Greg;
Back when the car was built that was the theory and the reason why is they had no other alternative. There are 2 facts about cars that will never change: the customer is always the R&D department and the vehicle technology will never be in sync with the desire of the manufacture and/or government mandates. So yes many cars have been working just fine with a little discharge at idle based on the technology of the day, but by today’s standards, not even close. The entire system works better at about 14 volts, you can see this when you step on the gas and the headlights get brighter. Components will last longer when running at 14 volts rather than 12 so it really comes down to how much you want it improved vs. how much you want it to look stock. I ran a 6volt +ground model A in parades, I we built a 75 amp GM SI alternator for it, the only reason for this is that I was honking the electrical mechanical horn constantly. The higher voltage and amperage resulted rebuilding the horn every 2 years rather than every year. Matching regulator to the alternator or generator if equipped is true and it is the sign of someone that knows what they are doing, although he probably also wanted to make sure there was nothing wrong with the regulator so it did not damage the unit he just built. The problem is the bench test only tells you if it works, nothing compares to installing it and testing it on the vehicle. The reasons for his is everything from the quality of your grounds, resistance in the cables, internal components, to size of the crank pulley which will be different from what is on the tester. We build alternators up to 325 amps, and charge up to $2500 to build some of them, and it is very difficult. We will spend hours test fitting rotors in stators, we look for ones that rub and hand file them down to get the tightest possible air gap. Rotating electrical unit are very inconsistent. Adjusting the regulator to the unit is the best way to compensate for inconsistencies in the unit.
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Location: Ontario, Canada | Darren, thanks for those details.
Greg |
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Location: Michigan | Ditto Darren, the insight is helpful. It won't be a daily driver. So I think I will be ok. |
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Extreme Veteran
Posts: 524
Location: West Jordan | Not a problem |
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Expert
Posts: 2312
Location: Arizona | Lots of good info. One of the things I read explaining the problem with generators is that with a generator ALL the current it generates has to go thru the brushes and that alone is a limiting factor for something sized to fit on a car. Trying to push 75 amps thru brushes that will fit inside a car sized generator just burns them up way too fast. With an alternator the "power" side of things doesn't go thru brushes, just the diodes, that's why a lot of the time the diodes are the weak point but at least they won't "wear out" from mechanical wear. |
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Extreme Veteran
Posts: 524
Location: West Jordan | Also why most generators have no output at an idle, reminds me that I probably should have mentioned the fact that the higher output ones can have output at idle, but the trade of is much shorter generator brush life. Most factory generators will little to no output at idle.
But the majority of all alternators still have brushes and they do have a limited life span. The difference is the brush rides on the slip ring of the rotor, but it only sees about 10 amps max. But diodes can have a short life span if driven at full output for too long, it is best to add up the power in your fuses or the amp loads and get an alternator that can produce 50% more than you need. It is not always possible but that way the alternator will work at 50% output and it will generate much less heat and last much longer.
If you know the wattage of the electrical device such as the stereo or if you want to play around with the volts vs. amps there is a calculator on our website:
http://rushps.com/tools.html
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Location: atlanta | Forget AC theory !, let's talk hole flow. |
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Expert
Posts: 1740
Location: Alaska | I had a buddy for years (gone now) who would argue "the holes flow don't you know". This may be too deep for some of the people here. ha ha |
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Charging system choices. Or everything you never knew you wanted to know about charging systems.
