Connecting car alternators in parallel

In summary: Alternators do not output perfect DC, but rather, a rectified AC waveform that has a frequency that depends on how fast the engine is turning. It's hard enough to synchronize (phase) two generators that output nearly the same frequency (and voltage) but imagine doing that with two car alternators that have frequencies that vary quite a bit!In summary, connecting two car alternators in parallel would likely not work because their frequencies would not be in sync and could lead to damage to the battery pack. Connecting three or four alternators in parallel would also not work because their frequencies would not be in sync and could lead to damage to the battery pack.
  • #1
agabrielauto
23
0
What happens if I connect two car alternators in parallel? Can I connect three or four alternators in parallel? I just want a cheap way to increase power. I need 5.5kw for recharging a battery pack.
 
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  • #2
I'm pretty sure that this is a bad idea; alternators do not output perfect DC, but rather, a rectified AC waveform that has a frequency that depends on how fast the engine is turning. It's hard enough to synchronize (phase) two generators that output nearly the same frequency (and voltage) but imagine doing that with two car alternators that have frequencies that vary quite a bit!

5.5 kW works out to 46 A (using 120 V) or 23 A (using 240 V)--even if you could find a charger, that's a lot of current (never mind what the charger's efficiency between wall to output is). You could probably use a big gas generator, but you'd still need something to convert the 120 V output to the appropriate voltage to charge the battery pack.
 
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  • #3
agabrielauto said:
What happens if I connect two car alternators in parallel? Can I connect three or four alternators in parallel? I just want a cheap way to increase power. I need 5.5kw for recharging a battery pack.

Is the battery pack only 12 volts total? This would be the only reason you would run the alternators in parallel with each other. And as MATLABdude pointed out, there are problems with that configuration.

If the pack is a group of 12 volt batteries in series then it would be feasible to place a single alternator in parallel with each battery. Though each alternator body would have to be electrically isolated from the others, as every alternator I've ever dealt with grounds the body.

If any of the alternator bodies were to come into contact with each other, it would generate a direct short circuit across a section of the battery pack, and major destruction, death, and/or putting your eye out, might ensue.
 
  • #4
I believe that 2 alternators with internal regulators of the same manufacturer and size can be paralelled without any problems. The fact that they don't output pure DC is irrelevant. The outputs are diode fed so nothing can feed back into the alternator. The battery which IS pure DC doesn't feed back into the alternator between pulses, so another alternator wouldn't either. I've seen more than one machine with dual alternators that came that way from the factory. The main thing to remember when charging battery banks with alternators is to NEVER disconnect the battery while the alternator is turning. Make sure the alternator has come to a stop before disconnecting.
 
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  • #5
Averagesupernova said:
I believe that 2 alternators with internal regulators of the same manufacturer and size can be paralelled without any problems.

In theory that sounds reasonable. But alternators are also belt driven. You would want the belt tensions balanced as well, using the same pulleys, etc.
 
  • #6
agabrielauto said:
What happens if I connect two car alternators in parallel? Can I connect three or four alternators in parallel? I just want a cheap way to increase power. I need 5.5kw for recharging a battery pack.

What sort of battery packs are you trying to charge?
 
  • #7
I suspect that it can be done, with care. In an alternator, the rotor has a dc excitation, and the stator output is ac, which is rectified by two diodes. Feedback is taken from downstream of the two doides and fed back to the rotor to control the output voltage. If you connect two alternators in parallel, the two feedback loops will interfere with one another, unless you isolate the two alternator feedback loops by putting one additional rectifier diode per alternator downstream of the feedback loop. This extra diode drop will require that the regulated alternator output voltages be increased by the same amount.
 
  • #8
Thanks for your answers!
It may sound crazy but I,m planning(in a near future) to test this connection in an electric vehicle:

1- DC electric motor with a special pulley adapter for connecting two high output alternators
2- alternators to DC/AC converter
3- converter to charger(ev charger)
4- charger to battery pack (96vdc)

Im just trying to extend the driving range!
 
  • #9
agabrielauto said:
Thanks for your answers!
It may sound crazy but I,m planning(in a near future) to test this connection in an electric vehicle:

1- DC electric motor with a special pulley adapter for connecting two high output alternators
2- alternators to DC/AC converter
3- converter to charger(ev charger)
4- charger to battery pack (96vdc)

Im just trying to extend the driving range!

Eeegads... Just add 6 more alternators. Batteries are like people: they are all different. A dedicated alternator for each battery, powered by regenerative braking, will optimize each batteries lifespan. All these converters will just add unnecessary time and expense to your project. KISS.

But then again, I'm poor... :cry:

Good luck. :smile:

Solar rules! :cool:


solarboat_2008April13_IMG_0064.JPG


Yes that's my freakin solar powered boat... Do you think I could make this stuff up?
 
  • #10
Can I do that and still connect all the batteries in serie to supply the 96 volts needed?
 
  • #11
OmCheeto said:
Yes that's my freakin solar powered boat... Do you think I could make this stuff up?

I don't see the motor...
 
  • #12
agabrielauto said:
Can I do that and still connect all the batteries in serie to supply the 96 volts needed?

Yes.

But as a reminder:
If any of the alternator bodies were to come into contact with each other, it would generate a direct short circuit across a section of the battery pack, and major destruction, death, and/or putting your eye out, might ensue.
 
  • #13
OmCheeto, this a draw I did representing the picture in my mind about what you are saying. It is correct? If not explain, please...
 
  • #14
Ups, is this one
http://gabrielauto.webs.com/apps/photos/photo?photoid=39042511 [Broken]
 
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  • #15
You could make up a shaft with several pulleys on it and drive an alternator from each pulley and charge a battery from each alternator.
Each alternator could have its own regulator like this.

So, you might have a big solid frame with a motor at one end and a bracket with a bearing on it at the other and a pulley shaft between the two. Then have alternators on each side of the shaft with their outputs going to batteries.

If the batteries were in series, you could leave them connected, but you would have to insulate the alternators from each other and put them in a closed box for safety.

If the batteries were in parallel, you would have to remove them for charging.
 
  • #16
agabrielauto said:
Ups, is this one
http://gabrielauto.webs.com/apps/photos/photo?photoid=39042511 [Broken]

Yes. That will work.
 
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  • #17
agabrielauto said:
Ups, is this one
http://gabrielauto.webs.com/apps/photos/photo?photoid=39042511 [Broken]

As Bob S pointed out, feedback is via field winding current. Where are your field winding connections, and what regulates each?
 
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  • #18
I can't wait until you explain me how it is posible. I'm always tempted to ask why things happen.
So here goes the question.
How it is possible to charge each battery(with its own alternator), while at the same time have them connected in series to power a controler(or electrc motor 96vdc)??
Isn't suppose to make a short circuit.
 
  • #19
As long as each alternator is electrically isolated from the others, the only path for charge to go is into its own battery. This assumes the batteries are not being used in a vehicle while they are charging, so there is no load on the batteries. It is charging from the mains.

It then behaves like a car alternator should, with its own regulator to stop charging when the battery is fully charged and to stop the voltage going too high.

Why do you see this as a problem?
 
  • #20
agabrielauto said:
I can't wait until you explain me how it is posible. I'm always tempted to ask why things happen.
So here goes the question.
How it is possible to charge each battery(with its own alternator), while at the same time have them connected in series to power a controler(or electrc motor 96vdc)??
Isn't suppose to make a short circuit.

Just pretend the alternators are batteries also. The circuit then becomes two sets of parallel series batteries.

The alternators have an added feature of having diode banks on their output. This prevents them from consuming power if their voltages drop below that of the batteries.
 
  • #21
As vk6kro said,
"This assumes the batteries are NOT being used in a vehicle while they are charging".
That's my point.
I do want to recharge the batteries while being used. Just like a normal car.
If that,s not possible, then I would have to go back to my first Idea(at the beginning of this forum).
The problem is the bigger alternator I have found is 350 amps.
And I need 500amps or 5.5kw.
 
  • #22
A very big problem, addressed earlier is
"If any of the alternator bodies were to come into contact with each other, it would generate a direct short circuit across a section of the battery pack, and major destruction, death, and/or putting your eye out, might ensue".
Unlike other generators or alternators, the automotive alternator has one side (usually negative) grounded to the case. This means that all the alternator cases have to be electrically isolated. But more important is the personnel safety issue. I heard of a guy who did not believe he could feel a shock from a 12 volt (or maybe it was 6 volt) auotmotive battery, so he soaked his hands in brine for several minutes, and then electrocuted himself. I suggest that if you plan to use this setup for a marine application, you do your boating in distilled water.
 
  • #23
OmCheeto said:
Eeegads... Just add 6 more alternators. Batteries are like people: they are all different. A dedicated alternator for each battery, powered by regenerative braking, will optimize each batteries lifespan. All these converters will just add unnecessary time and expense to your project. KISS.

But then again, I'm poor... :cry:

Good luck. :smile:

Solar rules! :cool:


solarboat_2008April13_IMG_0064.JPG


Yes that's my freakin solar powered boat... Do you think I could make this stuff up?

Is that an advanced DC motor, about 8 HP ?? Nice rig!

Now I know what I can do with that old Chrysler foot that has been laying in my back yard for 17 years:biggrin:
 
  • #24
RonL said:
Is that an advanced DC motor, about 8 HP ?? Nice rig!

Now I know what I can do with that old Chrysler foot that has been laying in my back yard for 17 years:biggrin:

:frown:

1(?) hp 12(?)vdc pride wheelchair broken(free!) motor that I fixed in about 15 minutes.

For research purposes only.
 
  • #25
agabrielauto said:
As vk6kro said,
"This assumes the batteries are NOT being used in a vehicle while they are charging".
That's my point.
I do want to recharge the batteries while being used. Just like a normal car.
If that,s not possible, then I would have to go back to my first Idea(at the beginning of this forum).
The problem is the bigger alternator I have found is 350 amps.
And I need 500amps or 5.5kw.

You would only want to use the alternators as a braking system. Otherwise it's a no win situation.

I would also test it out on a single alternator battery system to see if the idea is even valid.

Find out how much current each battery will accept at 70% DOD, 50% DOD, and 30% DOD.
This will give you an idea of how well the system will work at various depths of discharge.
Obviously, it's not going to do anything when the batteries are fully charged.
 
  • #26
This company http://www.zena.net/
Give me this answer on how they do it :
This system would comprise three of our SR200.12 Power Generators ($675 ea.), one WC.12B Master Control Module ($195), two WC.12S Slave Control Modules ($165 ea.), and one WC.VR2 Voltage Regulator Module ($190).
The three generators would be mounted so as to be driven by a single engine (though multiple engines can be used) -- typically be means of a single serpentine belt pulley mounted to the engine's drive shaft. The individual output terminals of the three generators would be connected together and with our electronic controls perform as a single generator (though more efficiently since we produce much less waste heat during the generation process.
The total cost of the system would be $2740
 
  • #27
This system would comprise three of our SR200.12 Power Generators ($675 ea.), one WC.12B Master Control Module ($195), two WC.12S Slave Control Modules ($165 ea.), and one WC.VR2 Voltage Regulator Module ($190).
The three generators would be mounted so as to be driven by a single engine (though multiple engines can be used) -- typically be means of a single serpentine belt pulley mounted to the engine's drive shaft. The individual output terminals of the three generators would be connected together and with our electronic controls perform as a single generator (though more efficiently since we produce much less waste heat during the generation process.
The total cost of the system would be $2740
 
  • #28
Do any of you thinks that I could do this (2 alternator outputs to perform as a single generator) in a much easy and cheap way?
 
  • #29
If you already have the alternators, why not just try it with one battery?
I think the regulators are just built into the alternators now.

Maybe it will all work OK. At least you can't hurt the alternators like that. They have diode outputs.

They may not share the load evenly, so maybe you could temporarily put meters in line to measure the currents from each alternator?
 
  • #30
OmCheeto said:
:frown:

1(?) hp 12(?)vdc pride wheelchair broken(free!) motor that I fixed in about 15 minutes.

For research purposes only.

Sorry Omcheeto,
Should have used a capitol A, Advanced DC, are the motors used in most electric car conversions. They come in power ratings as high as 20 HP.

I might have some thoughts for the OP, but will have to come back later.

Hope everyone has a good day.

Ron
 
  • #31
agabrielauto said:
Do any of you thinks that I could do this (2 alternator outputs to perform as a single generator) in a much easy and cheap way?

$2740 isn't cheap when you can buy a 7kw gas powered 120/240 vac electric generator for $400.

And if it were easy what you were trying to do, GM and Chrysler wouldn't be bankrupt right now.

RonL said:
Sorry Omcheeto,
Should have used a capitol A, Advanced DC, are the motors used in most electric car conversions. They come in power ratings as high as 20 HP.

I knew that. :tongue:

I'm familiar with the Advanced, Warp, and E-tec engines. Comes from hanging around the ev club geeks. I've even met John Wayland! (pat on back, pat on back)
 
  • #32
OmCheeto said:
$2740 isn't cheap when you can buy a 7kw gas powered 120/240 vac electric generator for $400.

And if it were easy what you were trying to do, GM and Chrysler wouldn't be bankrupt right now.



I knew that. :tongue:

I'm familiar with the Advanced, Warp, and E-tec engines. Comes from hanging around the ev club geeks. I've even met John Wayland! (pat on back, pat on back)

Took me a long time to see the light:blushing: doing the power part is easy, making it fool proof and idiot proof is where all the problems and expensive things come to the table.:wink:
 
  • #33
agabrielauto said:
Do any of you thinks that I could do this (2 alternator outputs to perform as a single generator) in a much easy and cheap way?

When it comes to electric motors and generators, you can get really creative, there are plenty of different components to connect or separate them in whatever way you need. Last time I priced alternators, a standard 95 amp unit cost between $75-100 USD. There is no way to short-cut the power to turn them, IMO the most important goal is the ability to recover energy that has been spent.

I have worked on battery connections and what you show in your drawing is most likely the best way. I have 12 batteries, and do not have the knowledge of electronics to build what I would like to have, that is a way to have them cycle one at a time.
What I see is, one is isolated and brought to full charge, while the other eleven (in various states of discharge) power the system. As the fully charged unit comes back on line the last and hopefully least charged one is isolated and charged. This continuous loop of charging would insure that each of the 12 batteries received the same depth of discharge and the same number of charges. I just can't see how to do this electronically without touching the batteries except to check for water.

The other thing I'm working on is the use of 2-1/2 HP treadmill DC motors. Putting 12 motors (30 HP total) 6 each on a jack shaft, the two jackshafts transfer 15 HP each to the drive system, the total weight of the motors, just under 100 pounds. Cost @ $20 each (surplus New) $360 USD. (for the skeptics, how often do treadmill motors have to be replaced?)

This compared to the Advanced 20HP motor, $1,700 USD at 140 pounds

The long skinny jackshaft, motor combination makes for a major space saving idea.

There are some other heavy ideas for the use of the treadmill motors in an EV, but for now, this should draw plenty of fire from the forum.:biggrin:

Later

RonL
 
  • #34
12 motors?. Do they all get conected to same controller?
 
  • #35
agabrielauto said:
12 motors?. Do they all get conected to same controller?

That's where I bogged down, I bought components to build individual controllers, but then my brain kinda goes a little bit in different directions and I can't decide on final plans. You can have all 12 run in one direction in unison, then you can set groups of 2 or 3 to run in reverse direction through clutch bearings, turning gear reductions of whaterever might be needed for low speed applications. A little like a 3 or 4 speed transmission. All this by simply reversing and splitting current flow.

I have a tendency to think myself out of project completions.

Crazy stuff, but there are times when the ability to split and separate individual motors into different actions will prove worthwhile in minimizing current flow.

RonL
 
<h2>1. How do you connect car alternators in parallel?</h2><p>To connect car alternators in parallel, you will need to first disconnect the negative battery terminals from both alternators. Then, connect the positive terminal of one alternator to the positive terminal of the other alternator using a heavy gauge wire. Next, connect the negative terminal of one alternator to the negative terminal of the other alternator using another heavy gauge wire. Finally, reconnect the negative battery terminals to both alternators.</p><h2>2. What are the benefits of connecting car alternators in parallel?</h2><p>Connecting car alternators in parallel allows for increased output power, as the combined output of both alternators is greater than the output of a single alternator. This can be beneficial for vehicles with high electrical demands, such as those with aftermarket sound systems or additional lighting.</p><h2>3. Can any two alternators be connected in parallel?</h2><p>No, not all alternators can be connected in parallel. It is important to make sure that the alternators have the same output voltage and are compatible with each other. Additionally, it is recommended to use alternators from the same manufacturer to ensure proper function.</p><h2>4. Are there any risks or drawbacks to connecting car alternators in parallel?</h2><p>One potential risk of connecting car alternators in parallel is that if one alternator fails, it can cause the other alternator to overload and also fail. Additionally, connecting alternators in parallel can also cause voltage imbalances and damage to the electrical system if not done correctly.</p><h2>5. Is it possible to connect more than two car alternators in parallel?</h2><p>Yes, it is possible to connect more than two car alternators in parallel. However, it is important to consult a professional and ensure that the electrical system is able to handle the increased output. It is also recommended to use alternators from the same manufacturer to avoid any compatibility issues.</p>

1. How do you connect car alternators in parallel?

To connect car alternators in parallel, you will need to first disconnect the negative battery terminals from both alternators. Then, connect the positive terminal of one alternator to the positive terminal of the other alternator using a heavy gauge wire. Next, connect the negative terminal of one alternator to the negative terminal of the other alternator using another heavy gauge wire. Finally, reconnect the negative battery terminals to both alternators.

2. What are the benefits of connecting car alternators in parallel?

Connecting car alternators in parallel allows for increased output power, as the combined output of both alternators is greater than the output of a single alternator. This can be beneficial for vehicles with high electrical demands, such as those with aftermarket sound systems or additional lighting.

3. Can any two alternators be connected in parallel?

No, not all alternators can be connected in parallel. It is important to make sure that the alternators have the same output voltage and are compatible with each other. Additionally, it is recommended to use alternators from the same manufacturer to ensure proper function.

4. Are there any risks or drawbacks to connecting car alternators in parallel?

One potential risk of connecting car alternators in parallel is that if one alternator fails, it can cause the other alternator to overload and also fail. Additionally, connecting alternators in parallel can also cause voltage imbalances and damage to the electrical system if not done correctly.

5. Is it possible to connect more than two car alternators in parallel?

Yes, it is possible to connect more than two car alternators in parallel. However, it is important to consult a professional and ensure that the electrical system is able to handle the increased output. It is also recommended to use alternators from the same manufacturer to avoid any compatibility issues.

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