Blade Runner Redux - Tesla Cybertruck!

[redpoint5]

The number of "tricks" available to improve the efficiency in an EV are way more limited than in an ICE. Avoiding the brakes matters a lot less with regen. There's not a discernable efficiency gain running more or less load on an electric motor, meaning rate of acceleration hardly matters. There's no "driving with load" or "pulse and glide".

Cruising speed and tire pressure (but mostly speed) tend to be the biggest efficiency factors. I doubt a significant difference in efficiency would be observed between my wife driving an EV, and me.

[freebeard]

The number of "tricks" available to improve the efficiency in an EV are way more limited than in an ICE.

ICE? That's a big tent.

Why Solid State Might Save The Combustion Engine

[Snax]

Originally Posted by redpoint5

The number of "tricks" available to improve the efficiency in an EV are way more limited than in an ICE. Avoiding the brakes matters a lot less with regen. There's not a discernable efficiency gain running more or less load on an electric motor, meaning rate of acceleration hardly matters. There's no "driving with load" or "pulse and glide".

Cruising speed and tire pressure (but mostly speed) tend to be the biggest efficiency factors. I doubt a significant difference in efficiency would be observed between my wife driving an EV, and me.

While the differences should be less, driving style can make a significant impact.

Some people see driving an EV as a free pass to efficiency, but that's not the reality.
Acceleration at a modest pace has an unavoidable minimum hit, but accelerating more briskly reduces efficiency, heating the controller, pack, and motor more. I can't really speculate exactly how much, but it's one of the things that makes racing my i3 less fun. (More than a couple of minutes of balls out driving puts it into overheat protection.) But what a lot of drivers in general fail at, EV or otherwise, is predicting traffic, and that can have a huge impact on regeneration potential as well.

More savvy EV drivers and us attempt to never use the brakes, while the less savvy are always throwing energy away by constantly tapping them or blasting up to stopped traffic and obviously throwing a good portion of energy away. Likewise, people who are constantly on and off the throttle also multiply the inefficiency losses over time, as even regeneration at best is still well under 90%. (80-85% is the number that is floating around in my head.)

So bad drivers still get bad efficiency and drag the numbers down.

[redpoint5]

Originally Posted by Snax

While the differences should be less, driving style can make a significant impact.

Some people see driving an EV as a free pass to efficiency, but that's not the reality.
Acceleration at a modest pace has an unavoidable minimum hit, but accelerating more briskly reduces efficiency, heating the controller, pack, and motor more. I can't really speculate exactly how much, but it's one of the things that makes racing my i3 less fun. (More than a couple of minutes of balls out driving puts it into overheat protection.) But what a lot of drivers in general fail at, EV or otherwise, is predicting traffic, and that can have a huge impact on regeneration potential as well.

More savvy EV drivers and us attempt to never use the brakes, while the less savvy are always throwing energy away by constantly tapping them or blasting up to stopped traffic and obviously throwing a good portion of energy away. Likewise, people who are constantly on and off the throttle also multiply the inefficiency losses over time, as even regeneration at best is still well under 90%. (80-85% is the number that is floating around in my head.)

So bad drivers still get bad efficiency and drag the numbers down.

I disagree that it makes much difference. You plot the route and maximum speed, then drive it as efficiently as possible, then have my wife thoughtlessly drive the same route with the same maximum speed, and you'll see no more than a 1% difference.

[freebeard]

Truly amazing, since one probably can't drive twice oneself and stand better than 50/50 odds. [/sarc]

Brakes =/= Regen

[Piotrsko]

So @redpoint5: you have done the testing to see if random driving a modern EV is only 1% different than max efficiency? Seems hard to believe that data would be so similar.

I also find it hard to believe you are able to measure that 1% accurately.

[Snax]

Originally Posted by redpoint5

I disagree that it makes much difference. You plot the route and maximum speed, then drive it as efficiently as possible, then have my wife thoughtlessly drive the same route with the same maximum speed, and you'll see no more than a 1% difference.

I think you were just blessed with a partner that is not a ****ty driver. Some people cannot predict the sunset past their view of the sun when you put them behind the wheel.

[aerohead]

Originally Posted by Snax

While the differences should be less, driving style can make a significant impact.

Some people see driving an EV as a free pass to efficiency, but that's not the reality.
Acceleration at a modest pace has an unavoidable minimum hit, but accelerating more briskly reduces efficiency, heating the controller, pack, and motor more. I can't really speculate exactly how much, but it's one of the things that makes racing my i3 less fun. (More than a couple of minutes of balls out driving puts it into overheat protection.) But what a lot of drivers in general fail at, EV or otherwise, is predicting traffic, and that can have a huge impact on regeneration potential as well.

More savvy EV drivers and us attempt to never use the brakes, while the less savvy are always throwing energy away by constantly tapping them or blasting up to stopped traffic and obviously throwing a good portion of energy away. Likewise, people who are constantly on and off the throttle also multiply the inefficiency losses over time, as even regeneration at best is still well under 90%. (80-85% is the number that is floating around in my head.)

So bad drivers still get bad efficiency and drag the numbers down.

According to MOTORTREND, the data collected by their test provider, Emissions Analytics, places kinetic energy capture regen efficiency at 81.1%. This is 'WHY' EPA 'CITY' is typically higher than EPA 'HWY'.
AeroStealth just got back from Wyoming ( to Las Cruces, NM ) in the Hyundai IONIQ 5. He said that once leaving Yellowstone N.P., heading south, down the Teton Range to Jackson Hole, he had gained mileage the whole way.
The GM engineer who designed the Chevy BOLT reported that regen was responsible for 40-miles of it's EPA COMB MPG rating.

[redpoint5]

Originally Posted by Snax

While the differences should be less, driving style can make a significant impact.

If we disagree, it's probably about the definition of "significant".

I'll arbitrarily pick 3% as my threshold for what constitutes a significant difference with driving technique alone, and confine the dataset to the middle 80% of the normal bell-curve distribution, tossing out those who drive like the gas and brake are on/off switches, and likewise those who only drive steady speed on the freeway, and therefore technique doesn't play a factor.

Acceleration at a modest pace has an unavoidable minimum hit, but accelerating more briskly reduces efficiency, heating the controller, pack, and motor more. I can't really speculate exactly how much

If you're thinking about it, might as well speculate.

But what a lot of drivers in general fail at, EV or otherwise, is predicting traffic, and that can have a huge impact on regeneration potential as well.

Even full self-driving fails to do this, ignoring the red light ahead and accelerating towards it despite sensing the red light.

It matters much less when you can get 80% of that back, though.

bad drivers still get bad efficiency and drag the numbers down.

What percent difference do you speculate driving habits (same cruising speed and HVAC use) alone account for?

Originally Posted by Piotrsko

@redpoint5: you have done the testing to see if random driving a modern EV is only 1% different than max efficiency? Seems hard to believe that data would be so similar. I also find it hard to believe you are able to measure that 1% accurately.

I have not, which is why I suggest the test, especially with a forum member so relatively nearby (I'll say hi to freebeard while I'm there).

Having difficulty measuring to 1% would only matter if that's how insignificant the difference is, which would reinforce my point.

Originally Posted by aerohead

...once leaving Yellowstone... he had gained mileage the whole way.

I've only twice brought the Prius plug-in from zero EV range, back to full using regen (only ~3 kWh), and that was one of the instances. Ended up wasting a good deal of energy downshifting since once the battery was full, it was no longer slowing the vehicle.

The GM engineer who designed the Chevy BOLT reported that regen was responsible for 40-miles of it's EPA COMB MPG rating.

My spidey senses tell me it would be a very extreme scenario where 40 of the 250 mile range is provided by regen. Now that I've made that assertion, I'll see if math tends to support it...

According to Fueleconomy.gov, the Bolt uses 28 kWh per 100 miles.

40 regen miles / 100 miles = 0.4
0.4 * 28 kWh = 11.2 kWh gained from regen

The way to think about that is to imagine 11.2 kW (15 horsepower) being regenerated for 1 full hour. Of course, slowing isn't just a one time event, but spread out over the full trip length, and capable of up to 70 kW (94 horsepower).

In a hypothetical scenario where one could achieve full regen for 1 continuous regen event that supplied the full 11.2 kWh of charge back to the battery, it would take nearly 10 minutes.

It seems unreasonable to me that the Bolt could, on average, gain 40 miles of range by regen. My guess would be closer to 4 miles of range, on average. Some trips would be zero, like steady freeway cruising, and others would be more than 4, like stop and go traffic.

[Hersbird]

Sometimes that regen is counted where a coast would have been a better idea. This is the problem with Teslas one pedal only setup. On a long highway trip no doubt maybe you could get 20 miles of regen BUT at the expense of 30 miles of coasting. I'm just picking numbers, but there is always a loss in the generation, storage, and then reapplication of power. The coast is just free movement. Normally when I'm driving on the freeway, I never once brake for 100s of miles but often need to let off the pedal and lose a bit of speed. I can also much better anticipate that compared to self driving which drives right up to the slowdown and brakes instead of just letting up 50 or 100 yards back.

Side note, got pulled over this weekend for Montana's new slow down and pull over for emergency vehicles law. I didn't think it applied to stuff going on on the opposite shoulder and didn't realize the law says to slow down 35 mph below the speed limit. Luckily just a warning because the new ticket is steep. I couldn't even see the police car stopped behind a pickup pulled completely off the opposite shoulder until I was right on it. I guess slam on the brakes and hope the guy behind me who can't even see the cars stopped over there sees my 70 to 35 mph speed decrease. The new rules are so vaguely worded and there are 3 different speeds depending on the road. From what I can tell if you are on highway 93 going through Darby where the limit goes down to 25 mph. If there is a tow truck or something you need to stop and go in reverse 10 mph to meet the 35 mph reduction.

Basically if traveling Montana slow way down if you see any lights until they work this out better.