Alternator as motor during acceleration?

[Logic]

Originally Posted by freebeard

One could bypass the battery pack with an electric turbocharger, but the heat kills the magnets.

Er..? I dont get it freebeard?

You want to cut charging while accelerating and thats when you'd want to turn on an electric turbo..?
Or do you mean those exhaust driven alternator/charger things?

[oil pan 4]

The smallest hybrid battery I recall was from first Gen prius. It was about 0.4kwh, but that hybrid drive topped out at like 34mph.

[freebeard]

Er..? I dont get it freebeard?

In the cold light of dawn, I'm not sure either. I know what I was on about (and why it wouldn't work), but I don't see that it applies to your situation.

Exhaust heat recovery system
An exhaust heat recovery system turns waste heat energy in exhaust gases into electric energy for batteries or mechanical energy reintroduced on the crankshaft.Wikipedia

[Ecky]

Originally Posted by oil pan 4

The smallest hybrid battery I recall was from first Gen prius. It was about 0.4kwh, but that hybrid drive topped out at like 34mph.

Pretty sure that was the usable capacity, while the actual pack was more like 1-1.3kwh.

~

I think lower hanging fruit is in improving alternator efficiency. Not that you can't do both, which is the point of a hybrid. But every step in the system is lossy, even in hybrids.

With an alternator you're looking at ~50% losses (give or take) when charging, then ~20-30% losses putting it into the lead-acid battery. Discharge efficiency depends on how fast you discharge the battery, but could be as much as 30%, and then you're looking at another ~50% (I guess?) loss using the alternator as a motor.

That gives a round trip efficiency of... what, 13%? Give or take? That's before even sending it through the transmission and tires.


The system really needs a permanent magnet motor with a controller, higher voltage, (preferably) a lithium battery, and a DC-DC converter for supplying the 12v electronics. That probably gives 5-6x improved efficiency. Once there, you have a hybrid with two entirely separate electrical systems.

That's not to say you couldn't do it with a 12v system alone, but as-is, 12v systems are set up so that you're floating the charge on the battery, and only enough electricity is being generated to meet the immediate needs of the car, which masks a lot of its inefficiencies.

Mazda apparently thought this was inefficient enough that they decided to put a supercapacitor pack in parallel with the 12v battery, and simply turn the alternator off now and then.

https://www.mazda.com/en/innovation/...y/env/i-eloop/

I expect it's more of a gimmick, but better than nothing if you're trying to incorporate stop-start with a conventional alternator and no high voltage system.

[Logic]

Originally Posted by serialk11r

Hub motors run at very low speed. Alternators run at 17000rpm. Huge difference.

Just look at the numbers for permanent magnet motor losses. It's not that bad, and you won't be spending a lot of time at high engine speed regardless. 10kW motor has a no load power consumption of 300-400W at maximum speed.

Alternators have field weakening, but they are so inefficiently designed from the start that it's not a big difference. They have inefficient cooling fans, significant rotor power consumption, and 4x the iron losses for the same magnetic field strength.

Erm; The number I recall is 6000 rpm for max output.
And thats alternator rpm.
The alternator pulley is generally less than half the crank pulley, so we're looking at more than double engine rpms..?
Dont recall a max efficiency #??

, so I went looking and found:
Improving Alternator Efficiency Measurably Reduces Fuel Costs
https://www.delcoremy.com/documents/...ite-paper.aspx
Still need to get to it, but from a quick scan it looks worthy of a thread of it's own!

Bicycle hub motors:
Ye much lower rpms
But my reading says motors designed for higher rpms are more efficient.
So too for alternator I would think..?

I thought of belting 2 hub motors to the inner CVs of a car.
Fabrication would be pretty easy.
Cost, control and lithium batteries; not so much.

That said
Here for example is a Tadpole Trike powered by 2 high rpm and efficiency Radio Control motors through a reduction box.

https://www.youtube.com/watch?v=WKAMus3oSdw

https://www.electricbike.com/50mph-m...lectric-trike/

Looks like a damn nice Motor/Alternator to me!
Just one of those coupled to the end of the crank pully..!?

I like this mentioned jump in efficiency when modding an alternator to 48 volts:
"...The efficiency (and power output) of an alternator can be improved markedly by moving to synchronous rectification and raising the output voltage using load dump configurations. For example a 48V 100A output may improve to almost 75% or better..."
https://electronics.stackexchange.co...configurations.

I haven't checked that yet???

A 48 volt system is nice and should simplify switching modes but Lithium is expensive.
Lead Acid for the 10?? seconds of acceleration?
Other?
Maths time.

[Piotrsko]

Based on MY personal experience in the home built E-ranger: battery chemistry doesn't matter for power, does matter for longevity and cost. My FLA pack cost approximately the same as the Volt pack I now use, but you only get 3years before they die. 7 years so far on the Lifepo4 I now have, half the weight 2/3 the size

[aerohead]

Originally Posted by Logic

Found this post
where a guy's talking about 8000 W from a normal alternator, when accelerating, with a ctlr and extra batteries. (100vdc)

Old post and the guy seems to have faded away. Site's dead etc.

I know newer cars have one way bearings on the alternator to use any rotational momentum it might have.
That wont work with this.

Then there's the 100 volts thing.
I'm guessing its a small pack if its only for acceleration but lithium isn't cheap or weightless.

Thoughts?

https://www.diyelectriccar.com/threa...s-motor.80547/

https://youtu.be/7iM6Oa8uh0k

1) At a nominal 12-VDC your at around 80-Amps.
2) Pushing the field up to create 100- VDC respects the 80-Amp barrier.
3) Which opens a question about the field 'conductor' capability.
4) At 90% efficiency, the alternator is handling 1,067-Watts of shaft energy ( 1.43-hp ).
5) Extracting 8,000-Watts ( 10.72-hp ) at the shaft would require 8,888-Watts (11.9-hp) of input energy from the belt.
6) 9,070-Watts ( 12.25-hp ) from the engine-to-belt.
7) Definitely a cog-belt system as freebeard has mentioned.
8) Clearance to the radiator/ shroud / radiator bulkhead would now be an issue.
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Personally, I'd be looking for a way to shave '12 1/4 hp' from mass, rolling- resistance, and aero.

[Logic]

Originally Posted by aerohead

1) At a nominal 12-VDC your at around 80-Amps.
2) Pushing the field up to create 100- VDC respects the 80-Amp barrier.
3) Which opens a question about the field 'conductor' capability.
4) At 90% efficiency, the alternator is handling 1,067-Watts of shaft energy ( 1.43-hp ).
5) Extracting 8,000-Watts ( 10.72-hp ) at the shaft would require 8,888-Watts (11.9-hp) of input energy from the belt.
6) 9,070-Watts ( 12.25-hp ) from the engine-to-belt.
7) Definitely a cog-belt system as freebeard has mentioned.
8) Clearance to the radiator/ shroud / radiator bulkhead would now be an issue.
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Personally, I'd be looking for a way to shave '12 1/4 hp' from mass, rolling- resistance, and aero.

My starting car is a Lotus Europa Special.
Basically a go cart with a fiberglass (flat bottom) body.
Not easy to shave more weight of 640kg - 1410lb.

It's also so low that there's a mad rush to get the windows closed when a Great Dane's thinking about lifting its leg against the car! (1.080m - 42.5 in)

https://en.wikipedia.org/wiki/Lotus_Europa
So pretty aero, but some room for improvement.

I don't want to nerf the car's looks or performance when you put your foot down. (worth more original, with removable bits)
A motor generator would help in that dept, as well as fuel efficiency.

So ye; efficient alternator, led bulbs, ram air intake, tuned length exhaust with anti reversion and a Pressure Wave Termination Box, etc is where I'm looking.

Aero:
I'm thinking headlight ..? fairings? what they called?
Side mirror delete with cameras.
Aero hub caps.
Perhaps some kind of rear deck fairing and rear wheel fairings.
The front spoiler alo looks like it could be improved.

[Piotrsko]

Headlight covers? Pot loads of aero improvements: front diffuser/airdam, fairing in the wheels, particularly the front, some sort of flow device for the step after the passenger compartment.

10 lbs of added improvements would not affect acceleration or handling by much.

[Logic]

Originally Posted by Piotrsko

Headlight covers? Pot loads of aero improvements: front diffuser/airdam, fairing in the wheels, particularly the front, some sort of flow device for the step after the passenger compartment.

10 lbs of added improvements would not affect acceleration or handling by much.

er... Seems you do more writing than reading?

This bit from previous post:
"I'm thinking headlight ..? fairings? what they called?
Side mirror delete with cameras.
Aero hub caps.
Perhaps some kind of rear deck fairing and rear wheel fairings.
The front spoiler alo looks like it could be improved."