Water Cooled Alternators

[Shel_B]

I've watched a few videos in which engines are equipped with water-cooled alternators. These have been on German cars, Mercedes and Audi, and none others that I can recall.

What's the reason for these alternators? They seem overly complicated considering that millions of cars do just fine with just regular alternators. Are these found on cars other than German models? It seems a bit risky to run water and electricity in such close proximity. What safeguards are taken to prevent disaster?

 

[Astro14]

I've watched a few videos in which engines are equipped with water-cooled alternators. These have been on German cars, Mercedes and Audi, and none others that I can recall.

What's the reason for these alternators? They seem overly complicated considering that millions of cars do just fine with just regular alternators. Are these found on cars other than German models? It seems a bit risky to run water and electricity in such close proximity. What safeguards are taken to prevent disaster?

200 amp alternators require cooling.

Regular cars, like a Camry, do fine with an air cooled 80 amp alternator.

But high end cars have the additional electric load from four heated seats, heated steering wheels, air conditioned seats, HID lights, and a bunch of other luxury features, in addition to the load your Camry has, and the regular alternator would be unable to provide the needed current.

Liquid cooling is more efficient. 15-20 times as efficient as air cooling.

This has been around for over 20 years. Nothing new.

 

[DemoFly]

I replaced a water cooled alternator on a 2000s Cadillac. Pretty simple to R&R. But, I couldn't help but think that my own jeep had more electronic equipment and was served fine by an air cooled 110a alternator.

 

[supton]

Any conversion of power is not 100% efficient. I don't know what those alternators are hitting, but 200A*14V is some 2800W. If it was 90% efficient it could be upwards of 300W having to be gotten rid of, while in a hot engine bay. Electronics tend not to like high temperatures.

Coolant may seem hot at 100C but the transfer is very good, as Astro14 points out. Auto electronics is creeping up there, 150C max used to be the norm but it's creeping up. They can pump a lot more of that waste heat, and more easily, with liquid cooling. Now they can "assume" the coolant will always be 100C (unlike so-called ambient air) and run the electronics under more consistent conditions.

[But as a typical luddite, you can guess it'll be a while before I have one of these under my hood. ]

 

[brianl703]

200 amp alternators require cooling.

Regular cars, like a Camry, do fine with an air cooled 80 amp alternator.

But high end cars have the additional electric load from four heated seats, heated steering wheels, air conditioned seats, HID lights, and a bunch of other luxury features, in addition to the load your Camry has, and the regular alternator would be unable to provide the needed current.

Police vehicles have a pretty high electric load. The police Crown Victoria has a 200-amp alternator. It's air cooled. I'd expect that most police vehicles are running air-cooled alternators.

 

[BMWTurboDzl]

I've watched a few videos in which engines are equipped with water-cooled alternators. These have been on German cars, Mercedes and Audi, and none others that I can recall.

What's the reason for these alternators? They seem overly complicated considering that millions of cars do just fine with just regular alternators. Are these found on cars other than German models? It seems a bit risky to run water and electricity in such close proximity. What safeguards are taken to prevent disaster?

BMW used them in the past (~20 yrs ago).

 

[MrHorspwer]

Police vehicles have a pretty high electric load. The police Crown Victoria has a 200-amp alternator. It's air cooled. I'd expect that most police vehicles are running air-cooled alternators.

2022 Chevrolet Tahoe w/ 9C1 police upfitter package has a 250A alternator.

Air cooled.

https://www.gmupfitter.com/wp-content/uploads/2021/09/2022-Police-Tahoe-9C1-Municipal-Specification-Guide-081721.pdf

 

[supton]

Dumb question: is there a size difference between a 200A water cooled and a 200A air cooled alternator?

 

[Chris142]

The Germans like to over complicate things. Have you ever seen an 80's Mercedes throttle linkage?

 

[Astro14]

Dumb question: is there a size difference between a 200A water cooled and a 200A air cooled alternator?

Huge difference.

No room at all for an air cooled alternator in the V-12 engine bay.

 

[supton]

Huge difference.

No room at all for an air cooled alternator in the V-12 engine bay.

I bet there may be a weight difference too.

I'd wager there is different design requirements & goals for a sports/luxury car and a police cruiser. With resulting compromises and tradeoffs.

 

[slacktide_bitog]

I've seen cars with oil-cooled alternators, when the valve cover gasket leaks oil all over the alternator

 

[Puhdantic]

They seem overly complicated..

Sounds about German.

 

[Astro14]

The Germans like to over complicate things. Have you ever seen an 80's Mercedes throttle linkage?

This isn’t an issue of over complicate.

600LBFT of torque. 500+ HP. Able to support 200 amps of charging from a compact alternator to fit that engine in a 2 seat convertible.

Specific engineering objectives require more advanced solutions.

Dumb engineering analysis - like “my diesel truck has bigger” - is just that.

Dumb.

Because it fails to take into account what the engineers were trying to accomplish. The M275 needed a liquid cooled alternator to make it all work. In a $180,000 luxury sports car, it makes sense.

In a run of the mill grocery getter, police cruiser, or regular truck, it does not.

 

[DemoFly]

Dumb question: is there a size difference between a 200A water cooled and a 200A air cooled alternator?

Yes. Water cooled are considerably smaller.

 

[nthach]

I replaced a water cooled alternator on a 2000s Cadillac. Pretty simple to R&R. But, I couldn't help but think that my own jeep had more electronic equipment and was served fine by an air cooled 110a alternator.

Buses used to use the Delco-Remy 50DN oil-cooled alternator. 270A at idle, oil lines from the engine fed it. Now they all use an air-cooled EMP 290/325A unit.

 

[Oillover]

I think it also has to do with the amount of available air circulation.

Vehicles over the past 20 years have become increasingly complex, with more and more items placed in the engine compartment.
When the alternator is now buried deep into the engine compartment, you'd better believe that's going to affect it's ability to be cooled by air alone.

 

[carviewsonic]

I wonder if the failure rate of air vs liquid cooled alternators is similar, or very different. Hard to know, since they're installed in different vehicles. Liquid cooled should last longer.
How about replacement cost of a liquid cooled alternator vs. air cooled? That might have more to do with the brand of vehicle than the alternator's design I suppose.
Maybe I've answered my own questions..

 

[4WD]

I bet there may be a weight difference too.

I'd wager there is different design requirements & goals for a sports/luxury car and a police cruiser. With resulting compromises and tradeoffs.

My son bought one of these - looks like a P&W PurePower (but trucks have space) …
They have undersized pulleys and hit more RPM’s …

 

[Craig in Canada]

The BMW E39 came both ways. My I6 528i had an air cooled alternator, but it had a scoop and duct line from the front bumper skirt directly into the rear of the alternator. It was not cooled by ambient underhood air, but with fresh air scooped from outside. The same year V8 540i (dad's) had a water cooled alternator. The water cooled unit never leaked or failed, going over 200,000km.

Lots of folks doing DIY bumper repair or conversion from "standard" to "sport" trim on their I6 failed to take into account the ducting to the I6 alternators and cooked them within a couple of months. Those air ducts could also ingest debris and pack it into the rear of the alternator - another thing to occasionally check and clean.