Improving Alternator EfficiencyMeasurably ReducesFuel CostsBYMIKE BRADFIELD, MSMERemy, Inc.

[Logic]

Interesting paper. Well worth a read:
https://www.delcoremy.com/documents/...ite-paper.aspx

Then I tried a search for "efficient alternator".
EVERY Alibaba seller has an alternator thats "super duper ultra extlemely velly -velly efficient!", as does the rest of the world.
Anyone found a legit source??

Astro Flight 3220 motors,designed for high-end RC models are 92% efficient, weigh 5lbs, and can put out up to 15-HP each (11,000-Watts)
https://www.astroflight.com/brushless-motors.html

With the right ctlr they should turn into motors during acceleration, that help fuel economy too.

Here's 2 of them on a trike:
https://youtu.be/WKAMus3oSdw
https://www.electricbike.com/50mph-m...lectric-trike/

[serialk11r]

It's impractical to swap in a high quality permanent magnet electric motor in as an alternator.

The auto alternator design is sort of reasonable for the application. Denso square windings have lower copper losses and active synchronous rectification reduces the rectifier losses. To generate higher current efficiently, generating a higher voltage at the alternator then stepping it down is more efficient.

[Logic]

Originally Posted by serialk11r

It's impractical to swap in a high quality permanent magnet electric motor in as an alternator.

The auto alternator design is sort of reasonable for the application. Denso square windings have lower copper losses and active synchronous rectification reduces the rectifier losses. To generate higher current efficiently, generating a higher voltage at the alternator then stepping it down is more efficient.

To quote the paper:
"...truck operating under the following scenario:
2,000 hours / year operation
100 amps average electrical current (14V system)
$4/gallon fuel cost
In this case it will cost over $1,000/year to generate on-board electricity. The
fuel cost difference between a 50% and 60% efficient alternator under this scenario is over $250/year.

So yes its impractical, but worth it maybe?

More Practical:

• As alternators seem to be most efficient at 2000 to 3000 rpm (from the paper) a simple ratio change for the alternator may be worthwhile?
  
• Switch off power to the rotor during acceleration if battery's charged enough?
  
• Aero modding the fan doodat, or 3D printing one?
  
• Cool air duct also seems to help some? (from the paper)
  
• Direct coupling to crankshaft end?

Anyone done any of these??

[Piotrsko]

I will add: generation devices are made to be efficient at generating, motors are efficient at making power. The designs of both preclude superior efficiency at other ends of their task.

[Logic]

Originally Posted by Piotrsko

I will add: generation devices are made to be efficient at generating, motors are efficient at making power. The designs of both preclude superior efficiency at other ends of their task.

I can see that with brushed motors yes.
Even with a mechanical variable advance for the brushes.

But from my reading, computer controlled (Arduino etc) brushless motors auto set all this field advance stuff for any rpm?
Any links plz?

[serialk11r]

The issue with PM generators (especially in gasoline engines) is that the amount of power available increases with rpm, but vehicles need the same amount of electrical power at idle. As the vehicle is moving and the engine is running many times higher than idle speed, the PM generator is running at very low load, and that's where PM motors/generators are not efficient.

I don't really understand magnetic hysteresis very well but I know eddy current losses (which dominate at higher speed) can be cut drastically if you spend more money making thinner laminations for the rotor. Money is hard to come by though :P

Basically, this is not stuff you can do in your garage. The most DIY-able way I can think of where you mostly work with hardware off the shelf is cycle a normal alternator between 0 field current and maximum voltage, charging a bigger lithium ion battery through a step down converter, and using a larger pulley on the alternator to reduce its speed.

I think you could probably raise the alternator efficiency 20% (relative) by doing this, while losing 10% charging the battery, so you'd still be ahead.

[Logic]

Originally Posted by serialk11r

The issue with PM generators (especially in gasoline engines) is that the amount of power available increases with rpm, but vehicles need the same amount of electrical power at idle. As the vehicle is moving and the engine is running many times higher than idle speed, the PM generator is running at very low load, and that's where PM motors/generators are not efficient.

True. But the extended idea is to use a lithium battery of some sort as a store for the energy produced at higher rpms, for use at those lower.
Also to run the generator as a motor during acceleration, charge allowing...

Originally Posted by serialk11r

I don't really understand magnetic hysteresis very well but I know eddy current losses (which dominate at higher speed) can be cut drastically if you spend more money making thinner laminations for the rotor. Money is hard to come by though :P

Yep; its an issue that can only truly be solved with an electromagnetic clutch for coasting... although a centrifugal clutch may work.
If one's buying an efficient motor/generator; the manufacturer's done the thin laminations already. But as you say; cost...

Originally Posted by serialk11r

Basically, this is not stuff you can do in your garage. The most DIY-able way I can think of where you mostly work with hardware off the shelf is cycle a normal alternator between 0 field current and maximum voltage, charging a bigger lithium ion battery through a step down converter, and using a larger pulley on the alternator to reduce its speed.

I think you could probably raise the alternator efficiency 20% (relative) by doing this, while losing 10% charging the battery, so you'd still be ahead.

Yep. get that low hanging fruit.
Rounding the edges of the fan thing with a file and sandpaper strips is also something I'd do.

There was a doodat on sale here that cut the power to the alternator's rotor field on acceleration.

It also 'opened' the aircon pump's clutch on acceleration.
No idea what difference it made or how the circuit 'decided' when you were accelerating.
An aircon's "ECON" mode does the same thing nowadays I think..? Or is it just a thermoset switch?