Of course with that loud a sound system you will not notice the motor/alternator sound very much.

If the TS has been listening to that level of music for awhile, he perhaps wouldn't be able to hear it anyway.

 

Yes, they apparently go as low as 55% efficiency.

That's less efficient than running a class AB amplifier off the mains!

 

It has not caught on because it is a dumb idea!

Why do you think that?
The 48V system would allow the use of smaller starter motors and smaller copper wires, which is likely a significant expense with the rise in the price of copper.
Going to 48V is the same as the reason cars went from 6V to 12V in the mid 1950's.

 

The 48 volt auto electrical system is pushed primarily by the sellers of the required pieces. It has not caught on because it is a dumb idea!

I respect your opinion a lot, but I strongly disagree on this one.
The reason for higher voltage is, as Cruts mentioned, is to lower the current.
Heck it is common usage even right now. Not 48 volts, but large trucks already use 24 volts, and for the same reasons: larger current requirements.

An acquaintance actually works in a BOSCH factory and they have plans to build a 400 amp alternator.
400 amps! That is really insane.

 

An acquaintance actually works in a BOSCH factory and they have plans to build a 400 amp alternator.
400 amps! That is really insane.

I am always suspicious of some of these high alternator current claims, it surely has to be for a very brief period only??
Especially when you look at the size of the stator windings and rectifier size?

 

Of course, it is peak current but it can be sustained, if not continuously, at least for a few minutes.
The unit was a real monster. At peak power, the field current could be 10 amps.

 

Consider the lighting load, in addition to the other loads, on some of those "BIG TRUCKS".
To provide battery charging along with the required lighting, a lot more capacity is required. Especially if a battery powered refrigeration system is included.
And certainly, to cover all conditions, the reserve capacity must be greater than the calculated demand by a fair margin.

 

I have a 110v 2hp motor that has 3450 Rpm. Can it spin a car alternator (180amp) ? The alternator will be doing it's intended job. Charging a pair of AGM batteries and supplying power for a 12v system (lights and car audio). Basically I just want the electric motor to be the car motor. Thanks in advance.

Hi,

This is actually a multifaceted question. It involves understanding motors, but also understanding alternators, and you can add to that pulley systems, and comparatively how it compares to a purely electrical system made just for this purpose and much more advanced.

The biggest question I can think of at the moment is how well the alternator works, as to what is the maximum voltage it can put out.
Alternators vary a lot like that, even though it's not talked about that much. Some alternators only put out maybe 14 volts even when being used in the original automobile they came from. That's not really enough to charge the battery correctly. Also, most of them will not charge the battery as well as the newer techniques can do, such as using a four stage charging method.
What this means is you can go through a lot of work getting it set up right and running, then find out it doesn't work that great anyway.
You can modify the output voltage by using the "diode fix". That's adding a diode to the alternator internally to fool the thing into thinking the battery is not yet fully charged and so it will charge it more than usual. You can look that up, but without that many alternators will provide for a very poor battery charge. Adding the diode improves the performance significantly, but it will never match the performance of a good battery maintainer that plugs into the wall.

You also have to get the pulley system right so you get the right shaft speed. The motor also has to be strong enough to allow the full output from the alternator, if that is really what you need. The efficiency also comes into question for a device that you have to use on a regular basis. This brings you down into dollars and cents needed to charge the battery.

The other thing to think about is this is going to be a mechanical device with moving parts that is going to replace a purely electrical device with no moving parts. That's not the way we usually want to go, we usually want to go from something that has moving parts to something that has no moving parts so we can improve the reliability and often at the same time, improve the performance.

I had done the same thing but with an automobile air conditioner compressor to make a paint sprayer. The compressor came from an old Cadillac so it had some pretty good performance. Four double acting pistons which you usually don't find on regular air compressors.

After all is said and done, this all "works" but how well it works depends on a number of factors, and it is very likely that it will never be as good as a battery maintainer and conditioner that can do four stage (or more) charging.

 

Spinning an alternator with a motor is no problem. Most auto parts stores have an alternator test stand which amounts to a motor turning an alternator as loads are applied. Using pulleys you can change your rotation speed. Finally since this system ran fine in the jeep it was in it should run fine using a battery and alternator. My wife had a 93 Grand Cherokee limited with a 500 watt Alpine system in it and it worked fine, granted you have a much more powerful system but again it ran fine in your jeep. Additionally I doubt you have run that system at full power, the actual power consumption is a function of volume. Have you actually measured the current drain for your amp at a few volume settings?

Ron

 

Hi,

This is actually a multifaceted question. It involves understanding motors, but also understanding alternators, and you can add to that pulley systems, and comparatively how it compares to a purely electrical system made just for this purpose and much more advanced.

The biggest question I can think of at the moment is how well the alternator works, as to what is the maximum voltage it can put out.
Alternators vary a lot like that, even though it's not talked about that much. Some alternators only put out maybe 14 volts even when being used in the original automobile they came from. That's not really enough to charge the battery correctly. Also, most of them will not charge the battery as well as the newer techniques can do, such as using a four stage charging method.
What this means is you can go through a lot of work getting it set up right and running, then find out it doesn't work that great anyway.
You can modify the output voltage by using the "diode fix". That's adding a diode to the alternator internally to fool the thing into thinking the battery is not yet fully charged and so it will charge it more than usual. You can look that up, but without that many alternators will provide for a very poor battery charge. Adding the diode improves the performance significantly, but it will never match the performance of a good battery maintainer that plugs into the wall.

You also have to get the pulley system right so you get the right shaft speed. The motor also has to be strong enough to allow the full output from the alternator, if that is really what you need. The efficiency also comes into question for a device that you have to use on a regular basis. This brings you down into dollars and cents needed to charge the battery.

The other thing to think about is this is going to be a mechanical device with moving parts that is going to replace a purely electrical device with no moving parts. That's not the way we usually want to go, we usually want to go from something that has moving parts to something that has no moving parts so we can improve the reliability and often at the same time, improve the performance.

I had done the same thing but with an automobile air conditioner compressor to make a paint sprayer. The compressor came from an old Cadillac so it had some pretty good performance. Four double acting pistons which you usually don't find on regular air compressors.

After all is said and done, this all "works" but how well it works depends on a number of factors, and it is very likely that it will never be as good as a battery maintainer and conditioner that can do four stage (or more) charging.

I also tried using an automotive compressor for spray painting. The oil mist can be filtered out, but the spray for 30 seconds then wait two minutes for pressure build up did not work.
And an alternator using an external regulator can be set wherever one wants. Not a big deal for those who know how. But the motor-generator scheme is so much less efficient.
The cheap trick is to get a bunch of surplus five volt supplies, 5 V 30 A, and adjust them to 4.3 volts and put then in series groups of three. 12 volt surplus is expensive, 5 volt surplus costs a lot less.

 

Some alternators only put out maybe 14 volts even when being used in the original automobile they came from. That's not really enough to charge the battery correctly. Also, most of them will not charge the battery as well as the newer techniques can do, such as using a four stage charging method.

A while ago I did some experimenting with an Delco Auto alternator off the vehicle.
I drove it from a powerful electric motor, with 12VDC fed to the rotor, the unregulated rotor produces around 60VDC from the 3ph rectified output.
The means of regulation was originally typically a Relay the would open and close as needed to regulate the voltage, later, the solid state version was used, but found to produce noise and whine in the car radio reception, to prevent this, the PWM version is now used.

 

Incidentally, the reason that the automotive industry went to alternators over the original DC generator, was the alternators very much higher output at low RPM's.

 

Incidentally, the reason that the automotive industry went to alternators over the original DC generator, was the alternators very much higher output at low RPM's.

Yes, I remember the concern when driving a car around town at slow speeds, that the battery would not be sufficiently charged from the old DC generators, especially in winter when more driving was done in the dark with lights and heater on.
You tended to keep an eye on the battery ammeter (cars had them then) to make sure the battery was mostly charging when you were driving. Sometimes you would rev the engine at a light to keep it charging.
Ah, the good old days (not).

 

My experience with automotive alternator whine is that the sudden onset of whine in a previously "quiet" system is probably an indication of a failed open rectifier diode. At least 3 times in the past 40 years . Certainly the ripple amplitude will be much greater with one diode not conducting.

 

A while ago I did some experimenting with an Delco Auto alternator off the vehicle.
I drove it from a powerful electric motor, with 12VDC fed to the rotor, the unregulated rotor produces around 60VDC from the 3ph rectified output.
The means of regulation was originally typically a Relay the would open and close as needed to regulate the voltage, later, the solid state version was used, but found to produce noise and whine in the car radio reception, to prevent this, the PWM version is now used.

A lot of modern alternators have a built in voltage regulator so you can't change the voltage without altering the voltage regulator in some way. A now common way to do this is to add a diode in series with the sense input so the control circuit thinks the voltage is about 0.5v less than what it really is, and thus raises the voltage by that much. That charges the battery enough.

For the comment about the 'generators' vs alternators, some of the alternators will also not charge enough with a quick drive around town simply because they voltage will never go high enough to properly charge the battery.

 

Yes, I remember the concern when driving a car around town at slow speeds, that the battery would not be sufficiently charged from the old DC generators, especially in winter when more driving was done in the dark with lights and heater on.
You tended to keep an eye on the battery ammeter (cars had them then) to make sure the battery was mostly charging when you were driving. Sometimes you would rev the engine at a light to keep it charging.
Ah, the good old days (not).

Hi,

Actually this happens with a lot of alternators too. The top voltage is close to 14.0 volts rather than something like 14.5 volts or greater, so the alternators will not charge the battery enough with a quick drive around town. In the past I've had several cars with this problem. The grounding bolt has to be super tight too or we don't even get that much.
Apparently the only way to correct this is to alter the voltage regulator built into the alternator. A common way to do this is with a diode placed in series with the sense input. The control circuit then thinks the battery voltage is around 0.5 to 0.7 volts lower than what it really is and so compensates by raising the voltage up by that much. That means more current to the battery which means a better charge. on short trips.

 

Before tampering with the regulation iit will make sense to check for a voltage drop in the charging circuit. This is done by measuring the DC voltage between the alternator output connection AT THE ALTERNATOR and the battery positive terminal AT THE BATTERY. if the difference is much more than 0.5 volts there is a poor connection someplace. Then do the same check between the alternator negative and the battery negative terminal.
One slightly poor connection will cause a problem that may be guessed to be a bad alternator or a bad battery. My experience was that it was a not tight enough nut on a terminal post. A half turn with a wrench solved the problem.

 

Before tampering with the regulation iit will make sense to check for a voltage drop in the charging circuit. This is done by measuring the DC voltage between the alternator output connection AT THE ALTERNATOR and the battery positive terminal AT THE BATTERY. if the difference is much more than 0.5 volts there is a poor connection someplace. Then do the same check between the alternator negative and the battery negative terminal.
One slightly poor connection will cause a problem that may be guessed to be a bad alternator or a bad battery. My experience was that it was a not tight enough nut on a terminal post. A half turn with a wrench solved the problem.

Yes I agree that is a good first test, but I have also seen that the original alternators or maybe the aftermarket stuff does not produce enough voltage simply because the regulator is not allowing enough voltage, and there is no adjustment like there used to be on some of the old DC generators in the much older cars (with separate voltage regulators).

The diode trick is common now but when I first started this with my older car it was not well known yet. It's a simple trick, but it involves taking the case apart, which I have done before anyway. The problem on some newer cars is that the alternator is very hard to remove from the car. I had a Volvo where the alternator was so hard to get off you had to take several other things off first, and unbolt other things too which made it so difficult to do I never attempted it.

Some people also swear that 14.1 volts is enough, but they drive to work back and forth every day of the week. For the occasional driver, this does not work.
I have watched the progress over months and months using a wireless battery voltage monitor and have accumulated data on how the battery voltage falls slowly over some weeks until it gets so low it may not start the car anymore. It can be a slow process, over four to eight weeks. I would take the battery inside the house to charge up with a power supply to get it back to good health again, but that would only hold for another month or two before I had to repeat that.

 

Just a thought... 48V automotive systems are going to cause a lot of headaches with devices melting, blowing up batteries while jump starting, and who knows what else because many people aren't even going to know the difference. Yes it will cost an arm and a leg to revamp everything to work with 48 Volts to start with, plus added production needs to produce parts for both voltages is going to be costly too.

I know in some areas large vehicles use 24 Volt, but there in the states 24 Volt systems are rare until you get in to huge equipment. You can parallel enough 12 Volt batteries to get done what needs done. Starting a big engine is usually what 24V is all about. Everything else will run just fine off 12 Volt. LED lights have done wonders for the current needs of large vehicles and equipment in general. Most semi trucks (again this is here in the state) only run a 160 Amp alternator anyways much like your normal passenger car.

For years alternators have put out less that 14 volts and kept batteries charged for years. The only difference between then and now is then there was no current draw when you shut the car off unless you left your dome light on. Now there is a small, but steady draw at all times. Charging voltage is not the problem... the problem is leaving your car sit unused for too long.

 

Just a thought... 48V automotive systems are going to cause a lot of headaches with devices melting, blowing up batteries while jump starting, and who knows what else because many people aren't even going to know the difference. Yes it will cost an arm and a leg to revamp everything to work with 48 Volts to start with, plus added production needs to produce parts for both voltages is going to be costly too.

I know in some areas large vehicles use 24 Volt, but there in the states 24 Volt systems are rare until you get in to huge equipment. You can parallel enough 12 Volt batteries to get done what needs done. Starting a big engine is usually what 24V is all about. Everything else will run just fine off 12 Volt. LED lights have done wonders for the current needs of large vehicles and equipment in general. Most semi trucks (again this is here in the state) only run a 160 Amp alternator anyways much like your normal passenger car.

For years alternators have put out less that 14 volts and kept batteries charged for years. The only difference between then and now is then there was no current draw when you shut the car off unless you left your dome light on. Now there is a small, but steady draw at all times. Charging voltage is not the problem... the problem is leaving your car sit unused for too long.

Perhaps, but I've proved time and time again with several cars and power supplies and battery chargers and battery maintainers that 14 volts is not enough to fully charge a flooded cell lead acid battery.

What I think happens is that a 50 percent charge will still start a car so many people who drive back and forth to work every day never realize that their battery is only 1/2 charged most of the time. Sure, it still starts the car, but it is not happening with the full cranking power.

If you check all over you can find SOC data on this and it will say 14v is fairly low (and 12v resting voltage is too low). Is there a chance that the battery will last longer this way overall. If it starts the car most people will never bother to check the true SOC, and never check the lifetime of the battery vs what it should be able to do. I had cheap batteries last more than the warrantee period maybe because they never fully charged.

Also, if you check the voltage of a brand new battery, it will always be around 12.6 volts. If it is being charged at only 14v that voltage (that 12.6v is sometimes referred to as the 'resting' voltage) will fall down to 12v or even less over time. The resting voltage has to be checked after the battery has stopped being charged preferably after 24 hours. Some people check it after 30 minutes, but I do not think that is long enough.