Upgraded Steering Wheel with Paddle Shifter Regen Mode?

[Curly]

Yeah, that's what intuitively makes sense. But what the hybrid owners figured out was that there are hotel loads (electricity used for things other than propulsion) which are present when you have the accelerator down, but disappear when you're coasting.

Sure, there is electricity used for things other than propulsion, but I would expect that would occur independently from the accelerator position. Can you give a specific example of what you are describing?

 

[Curly]

But what the hybrid owners figured out was ...

You keep referring to hybrid owners, but we're not driving hybrids; we're driving EVs. Isn't it possible that the effect you're describing applies specifically to hybrids, with their more complicated, dual-power-source drivetrains?

 

[f1geek]

You keep referring to hybrid owners, but we're not driving hybrids; we're driving EVs. Isn't it possible that the effect you're describing applies specifically to hybrids, with their more complicated, dual-power-source drivetrains?

I agree. E-Golf is not a hybrid. We need real world testing. Who is going to do it?

 

[Josip Buljac]

Hi.
I just installed a Golf 7R steering wheel into my e-Golf 2019.
I really like the rounded airbag style and it really changed the look of the interior a lot.
Now to the point. My R steering wheel also came with the paddles for shifting gears. As the e-Golf doesn't have gears I was hoping to be able to regulate the regeneration of battery power. Did anyone else tried to code it to work?
Everything worked as normal after swapping the steering wheel except the paddles...

 

[Solandri]

I think what I'd want most is a "maintain the current speed using regenerative braking" mode. I've mainly been using only D and B modes in daily driving. I only touch D1-D3 on long downhill stretches where I want to use regenerative braking to maintain speed. Manually figuring out which D[1-3] mode will come closest to maintaining speed is annoying. And sometimes the slope of the hill changes as you go down. I've figured out the pattern for the hills closest to my house that I hit frequently. But figuring it out for new locations is a chore.

Someone suggested trying cruise control. And it works! If you set cruise control for 40 mph, when you go downhill the car will automatically engage regenerative braking to maintain 40 mph!

 

[Josip Buljac]

I have test driven the Skoda Enyaq an it had the paddles for regent. And it was a great experience and option. Highly recommend if you like to actively use the reGen. during driving to minimize the power consumption.

 

[Solandri]

You keep referring to hybrid owners, but we're not driving hybrids; we're driving EVs. Isn't it possible that the effect you're describing applies specifically to hybrids, with their more complicated, dual-power-source drivetrains?

I think I figured it out. The peak efficiency (dark red) for most EV/hybrid electric motors is towards the upper edge of the upper-center portion of the torque-RPM range. (Source for the image: https://www.researchgate.net/public...nd_Batteries_for_Electric_and_Hybrid_Vehicles )



Unfortunately the y-axis is in toque. I'm not sure how the RPM maps to MPH. (I tried it for if the motor were directly driving the wheels, and for a Golf's tires it works out to only 807 RPM at 60 MPH. So there has to be some gearing in there.) I know most cars need about 15-30 hp to maintain highway speeds. But without knowing the RPM of the electric motor at that speed, you can't convert hp to torque.

So the other way I can think of figuring this out is to map the top RPM to the e-Golf's top speed (~90 mph, bit less for 2015-16, bit more for 2017+). At 60 mph you're about 2/3 of the way up the RPM range (since the car has no transmission). Which as you'd expect is right about where the peak efficiency range sits - exactly how you'd design a car which will spend a large fraction of its time at highway speeds.

But since the hp needed to cruise at constant highway speed only requires about 17% to 20% the motor's max hp (134 hp and 115 hp respectively), that probably puts you down around 20%-25% the peak torque at that RPM (accounting for it being slightly off the peak of the hp curve). Depending on motor, that's slightly to well below the peak efficiency range. Since your speed (RPM) is constrained, to get up into the peak efficiency range, the motor needs to deliver more torque. But that makes your car accelerate.

So you end up in a situation where averaged over time, cruising at constant speed (low torque, lower efficiency) burns more energy for the same average speed than accelerating to above your target speed (high torque, higher efficiency), then coasting for a while (no energy).

If you wanted to be really gimmicky, you could add a second motor whose efficiency peak is right at the torque and RPM needed to maintain highway speed. But I suspect the cost and weight make that non-optimal. And if you use that as your main motor, it likely doesn't have enough overhead for you to be able to accelerate briskly while at highway speeds. So you pretty much have to use a bigger electric motor, which ends up making it more efficient when you hypermile, than if you maintain constant speed.

Edit: You can also see why jackrabbit starts burn so much energy. You're at the upper left corner of the torque - RPM curve, which corresponds to lowest efficiency.

 

[Fugazi]

Unfortunately the numbers in the graphs are hard to read. But if you look very thoroughly, you will see that the difference in efficiency isn't that big. Totally unlike IC engines.
Graph C (Nissan Leaf) is easiest to read and you'll see that the efficiency is between 94 and 97% in most conditions.

The 2017 e-Golf has a fixed gear ratio of 2.7 and 3.61 for the final gear. So with 9.96 total gear ratio and 205/55R16 tires 3000 rpm is 35 km/h. And top speed of 140 km/h is done at 12000 rpm.

At 80 km/h you need roughly 10 kW and this means at 7000 rpm about 13-14 Nm. And efficiency (again for the Nissan) is down to roughly 90%.
To improve the efficiency (by quite little) the gear ratio would need to be longer. But as the car has only one gear it would be really bad for the acceleration.

Tesla plays with the motors to improve fuel efficiency.

You will only be in the upper left corner when accelerating full from standstill. After that rpm increases linear with speed and torque is adjusted with the go pedal.