Water cooled, high amp 12v alternator

[SoonerSailor]

I think your calculations are correct. Rectifier losses are not large compared to an alternator that is only 50% efficient. There are alternators with efficiencies close to 75%, but I know nothing about them.

[team karst]

Dont forget that there are 6 power diodes wired to a three phase winding set. The current thru the diodes is highly time variant thru the revolution cycle of the rotor.
Other losses: windage, bearing friction, the entire field current, plus I sq R of the 3 phase windings. And, we havent left the inside of the case yet.

[goboatingnow]

There are 4 major heat sources

1. IsquarecR winding losses
2. Dissipation in the diode trio
3. Regulator dissipation
4. Mechanical friction

Moving 2. & 3 to external locations helps a lot

[kenbo]

Wouldn't #2 be the bridge rectifier rather than the diode trio?

[kiwin]

Has anyone tried electrodyne alternators?

[team karst]

The diode trio doesnt deal with much current. OTOH, those other 6 do the heavy lifting.
Although, ALL the power going thru the diode trio ends up heating the field winding.

[goboatingnow]

Originally Posted by kenbo

Wouldn't #2 be the bridge rectifier rather than the diode trio?

Sorry yes a meant to put the trio with the regulator

[baltic sailor]

Alternators have changed in last 10 years. All the fancy regulators like the Balmar are already incorporated into most modern generators.
https://www.bosch-motorsport.com/con...tor_B3_LIN.pdf
This one is an example for a racing car and already a few years old. As you see it´s controlled by the LIN Bus. Most cars today are controlled by LIN Bus,
With Lifepo4 its difficult to limit the charge current...my problem at moment. That's why I ´m looking for another alternator. The big loss on the rectifier diodes is no more true either. It has all changed. Temperatur is 85 degrees...
Belt manager is done by the controller. Look at the Lin commands. The big companies are focused on read the application careful. Somebody needs to build a small box with a micro to do the controlling. The special companies are all focused on the RV market, boating is only a small market.
My french car has a small alternator ...since it´s a diesel and heating is electric, the generator has to produce a lot of Amps. At the moment I use a DC-Dc to charge the Lithium....next project is a different alternator for the boat.

[lmxr]

Originally Posted by Dan Kimblad

It's true that moving the rectifier externally is much easier and will certainly lower the temperature. I have not thought about that, but how much lower will the temp be?
If we have bad diodes that have 0.7 volts in drip, it will be 70 watts at 100 Amp (please correct me if I am wrong about this).
[...]

I often read about alternators running much cooler after the rectifier has been removed and mounted externally, yet as you show the math doesn't really work out unless the alternator would be a very efficient one, in which case it would run cool anyway I guess.

I wonder whether removing the internal rectifier greatly improves the airflow through the back of the alternator, thereby lowering the temperature for the same output current simply by improving the ventilation?

[lmxr]

Originally Posted by baltic sailor

Alternators have changed in last 10 years. All the fancy regulators like the Balmar are already incorporated into most modern generators.
https://www.bosch-motorsport.com/con...tor_B3_LIN.pdf
This one is an example for a racing car and already a few years old. As you see it´s controlled by the LIN Bus. Most cars today are controlled by LIN Bus,
[...]

Hmm, the datasheet mentions "Typical lifetime before service: max. 6,000 km / 30 h".

I hope that 30 h lifetime is a typo, or does it mean something else?

[team karst]

The problem statement, as I see it, is that automotive/racing alt. designs optimize size, weight, and cost over efficiency. Yes, the regulators are now "smart", or at least controllable. However, these rather horrendous efficiencies are due to small stator wire. Yes, they can push tremendous currents, for a while, with the ubiquitous 3 phase windings with high air flows. But, if you compare a 3 phase induction motor rated at 200 Amp INPUT, with a lightweight alternator rated at 200 Amp OUTPUT, there are huge differences in copper wire size. A motor runs at near 90% efficiency, a number that alternators are not even close to.
One thing that will very much help is going away from 12V and towards 48V. Now, you have 4x the energy conversion with similar copper losses. Its this low voltage demand that makes this a difficult problem to engineer around.

[Dan Kimblad]

Hi
So satisfyed
Remowed rectifier and water cooled it seperately .
Running perfectly the whole summer.

https://youtu.be/9CrBNP1dqzs

After an hour it charge 225Amp and temperature is 42C inside the alternator.

I name it ”Kimpower”

[skipperpete]

Hi Dan, well done. Did you use raw water for cooling or fresh? The YouTube vid didn’t work on my iPhone but I’ll try later with a desktop.

[Cheechako]

Originally Posted by Dan Kimblad

Hi
So satisfyed
Remowed rectifier and water cooled it seperately .
Running perfectly the whole summer.

https://youtu.be/9CrBNP1dqzs

After an hour it charge 225Amp and temperature is 42C inside the alternator.

I name it ”Kimpower”

but.... what was the battery temperature !? Most hi output alternators shut down due to battery temp, not alternator failure...

[SailingHarmonie]

Just because many people here haven't heard of water-cooled alternators doesn't make them especially rare or exotic.

I have a WhisperPower DC generator with a water-cooled permanent magnet alternator that outputs 150 Amps at 24DC, 3.6 kiloWatts, way bigger than most drive engine powered alternators. The big benefit here is it can run at full rated output for as long as needed without ever overheating. It is cooled with the engine coolant, so it runs at a steady ~80C or so. It also does all of its rectifying and voltage control in an external box, although that heat load is not large. Not really any different than a similarly sized line-powered battery charger, which is basically what it is.

Permanent magnet alternators are more amenable to water-cooling. The magnets themselves don't really generate heat, they are on the moving rotor, so you can just let them spin and not worry about cooling them. You just cool the coils on the stator where the heat is coming from. A permanent magnet alternator is also MUCH more efficient at converting mechanical energy into electrical power, so there is significantly less waste heat to start with.

A field coil alternator makes a significant amount of its waste heat in the rotating field coils. Those can not be (easily) water cooled, so you still need to blow air through it to keep them from melting down, and that partially defeats the purpose of the water cooling.