Author Topic: Electric Car Experiences  (Read 13538 times)

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Offline richard.cs

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Re: Electric Car Experiences
« Reply #150 on: August 13, 2019, 11:09:36 am »
Yes, it's a difficult to solve equation for any EV manufacturer.
I see that there are costs in making it flexible but it's not that difficult. The Renault Zoe for example just takes the three phase input to a three phase bridge and converts directly to DC, then has a contactor that shorts N to L3 if there's no voltage on the DC output but there is voltage L1-N in order to enable single-phase charging. The contactor is a little odd when they could have just added two more diodes to the bridge and had a permanent neutral connection. The 22 kW and 43 kW models both work the same just with 32 and 63 A maximum phase current (and it seems like 63 A single-phase charging would work in principle on the 43 kW model, as would things like a charge point that only supplied L1 and L2 without N or L3).

The extra cost for supporting 3 phase is a couple of extra diodes in the input stage (trivial), extra current transformers, etc. (moderate?) and a higher voltage rating for many of the components (probably the significant one). US model cars with type 1 connectors just can't have 3 phase because it's inherently a single-phase standard and doesn't have the required number of pins.

Some EV manuf. like BMW or renault build in only 1 phase chargers on the base model, so charging at a 16A/3ph is limited to 16A/1 phase -> 3kW
Of course if the charger were single phase but could work with higher voltages it would be able to charge between phases and give sqrt(3) faster charging, but it's likely the component voltage rating that is the restriction. I am somewhat surprised European manufacturers are skimping on the charger to that extent given that 16A 3 phase is such a common charger in Europe.
 

Offline f4eru

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Re: Electric Car Experiences
« Reply #151 on: August 13, 2019, 11:21:11 am »
The extra cost for supporting 3 phase is a couple of extra diodes in the input stage (trivial), extra current transformers, etc. (moderate?) and a higher voltage rating for many of the components (probably the significant one).
Unfortunately not.
You can't do that with diodes. The power factor would be extrelmely bad, and that's not allowed by regulation.
You'll need a multi-kW isolated SMPS per phase with a continuous rating, a high immunity to surges, not too heavy, and acting as a PFC. That has quite some cost.

Quote
The Renault Zoe for example just takes the three phase
anyone has the specs for 1ph and 3ph charging of the zoe ?
 

Offline richard.cs

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Re: Electric Car Experiences
« Reply #152 on: August 13, 2019, 12:27:02 pm »
You can do active PFC on the secondary side of a 3 phase bridge reasonably well so long as there is no capacitance before the converter. It's not perfect because you can't draw current from the lowest voltage phase but you can achieve pretty good conduction angles. Certainly much better than you can achieve on a bridge which is capacitively loaded.

I have seen a diagram for the input structure of the Zoe where the first thing it hits is a three phase bridge, with a L3-N contactor. Of course this wasn't official Renault documentation so maybe it's incorrect or an over-simplification. What is well-documented is that it reused the motor driver and the motor windings as the 43 kW AC charger, I imagine there are plenty of patents describing this if one wanted to go digging.

A 5 minute search found this: https://www.pes-publications.ee.ethz.ch/uploads/tx_ethpublications/__IPEMC_2012_Seminar_3ph_PFC_Rectifiers_FINAL_as_sent_310512.pdf which describes a large number of different three-phase PFC topologies, quite a few with a simple bridge input. I had assumed that the Zoe was something like p29, bridge followed by current-mode switcher giving ~square wave input current with 1/3 dead time. This sounds pretty ugly but the power factor of this is claimed to be 0.952. There are also approaches like on p10 where it is a simple bridge but 3rd harmonic is artificially injected back into the inputs.

(did some digging, it looks like what I read before was an over simplification and the Zoe uses a controlled rectifier as per this patent: https://patents.google.com/patent/US20120286740/en)
 

Offline f4eru

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Re: Electric Car Experiences
« Reply #153 on: August 13, 2019, 12:58:53 pm »
OK, Interesting PFC topologies :)
 

Offline richard.cs

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Re: Electric Car Experiences
« Reply #154 on: August 14, 2019, 09:02:58 am »
And a bit more on-topic...

I've been driving the Zoe about 13 months and 10,000 miles now. It basically just works. Most charging is at home overnight with occasional top-ups at other times, e.g. after work if we're going out again. Some use of public chargers with the main problem there being the fragmented ownership of them in the UK - there are dozens of different "charging networks" and for each one you have to sign up, often install an app, and pre-load an account with £10 or so. I just want to be able to show up, pay and charge, charge points with contactless payments would be good there.
 

Online coppice

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Re: Electric Car Experiences
« Reply #155 on: August 14, 2019, 11:40:40 am »
And a bit more on-topic...

I've been driving the Zoe about 13 months and 10,000 miles now. It basically just works. Most charging is at home overnight with occasional top-ups at other times, e.g. after work if we're going out again. Some use of public chargers with the main problem there being the fragmented ownership of them in the UK - there are dozens of different "charging networks" and for each one you have to sign up, often install an app, and pre-load an account with £10 or so. I just want to be able to show up, pay and charge, charge points with contactless payments would be good there.
Have you had much trouble turning up at a charger and finding its dead? There seem to be a lot of dead ones around, and as a casual observer the various apps don't seem to be very thorough in showing them.
 

Offline richard.cs

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Re: Electric Car Experiences
« Reply #156 on: August 14, 2019, 11:51:32 am »
Have you had much trouble turning up at a charger and finding its dead? There seem to be a lot of dead ones around, and as a casual observer the various apps don't seem to be very thorough in showing them.

It's not happened yet. I have though actively avoided ones marked as dead in ZapMap. One petrol station near my got a rapid charger and then proceeded to only switch it on when people went in and asked for it, but they stopped that sillyness after a few weeks. ICE cars parking in the way seems to be more of a problem. Supermarkets in particular seem to have the problem of putting the chargers near the building (probably because that's where the power is) but then the spaces end up being desirable, in close to the entrance with the disabled and parent & child bays, so people just park in them and the only parking enforcement they do is time-of-stay.

 I've not yet been unable to charge anywhere that was marked as working, but having multiple bays and chargers in most locations helps there.
 

Online coppice

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Re: Electric Car Experiences
« Reply #157 on: August 14, 2019, 12:08:59 pm »
Have you had much trouble turning up at a charger and finding its dead? There seem to be a lot of dead ones around, and as a casual observer the various apps don't seem to be very thorough in showing them.

It's not happened yet. I have though actively avoided ones marked as dead in ZapMap. One petrol station near my got a rapid charger and then proceeded to only switch it on when people went in and asked for it, but they stopped that sillyness after a few weeks. ICE cars parking in the way seems to be more of a problem. Supermarkets in particular seem to have the problem of putting the chargers near the building (probably because that's where the power is) but then the spaces end up being desirable, in close to the entrance with the disabled and parent & child bays, so people just park in them and the only parking enforcement they do is time-of-stay.

 I've not yet been unable to charge anywhere that was marked as working, but having multiple bays and chargers in most locations helps there.
I think the placement of charging stations near the building is partly for convenient wiring, but there are other factors. They'd need at least one space near the building as a disabled space, or people would complain they aren't supporting disabled people properly. However, the disabled sticker situation in the UK is insane. Supermarket car parks have at least 10% of their spaces set out as disabled spaces. There used to be just 2 or 3, and they were not always in use.

Companies putting chargers in their staff car parks generally place them in a very desirable (i.e. short walk) part of the car park. I think its considered a perk of driving an electric car.

 

Offline richard.cs

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Re: Electric Car Experiences
« Reply #158 on: August 14, 2019, 12:28:24 pm »
Supermarket car parks have at least 10% of their spaces set out as disabled spaces. There used to be just 2 or 3, and they were not always in use.

Not in the Southampton area they don't, 10 spaces out of perhaps 300 seems normal around here, with perhaps a further 20 for parent and child.
 

Offline tom66

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Re: Electric Car Experiences
« Reply #159 on: August 19, 2019, 03:47:00 pm »
Do quite like my VW Golf GTE PHEV.

For short journeys, which represent 90% of my mileage, it's fantastic.  Long term fuel economy is >200mpg (<1.2L/100km)

Electric economy is around 17kWh/100km but if I drive sensibly in summer weather with just the fan/air con on low it gets around 14.5kWh/100km or better.

Likes:
- The regen braking, the instant torque, and smoothness of drivetrain
- The hybrid petrol-electric combination for acceleration (210 hp is enough to make a dent when trying to overtake)
- Adaptive cruise and auto hold are so smooth and well put together
- Cost of running on electric is dirt cheap
- Petrol engine is surprisingly efficient (~50 mpg is possible if driven sensibly with summer tyres)

Dislikes:
- DSG gearbox can be a bit clunky (shifts are a little jerky), especially when cold (think it's related to the DSG clutches and the oil) 
- DSG gearbox isn't great at going from high gear to low gear quickly (e.g. 20 mph approach onto a roundabout and rapid acceleration) but this can be reduced by paddle shifting down before.  Yes, the car uses the gearbox in e-mode, which is odd!
- HV battery has had recall already which resulted in replacement due to poorly fitted weather seal (93C3 recall action) but bonus was new HV batt at 51,000 miles
- Adaptive cruise sometimes doesn't get the braking right in traffic on hills which results in a tiny bit of rollback when setting off but nothing serious
- Range in winter is quite a bit poorer with only the resistive heating and poor cabin insulation
- Overall range of the car is quite poor, which is fine for my uses but means waiting for a charge to use e-mode again (e.g. pop home and stop for 1.5 hours to wait for charge before going on a journey, or finding a shopping centre with charging.) The car has a petrol engine, but I like to minimise the use of that!
- Service schedule is same as regular Golf despite low engine use; ultimately cost of annual maintenance is similar, although fully synthetic oil recommended which is extra.
« Last Edit: August 19, 2019, 03:51:33 pm by tom66 »
 

Offline boffin

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Re: Electric Car Experiences
« Reply #160 on: August 19, 2019, 05:18:57 pm »
Do quite like my VW Golf GTE PHEV.

For short journeys, which represent 90% of my mileage, it's fantastic.  Long term fuel economy is >200mpg (<1.2L/100km)

Thanks for the info.  The PHEV Golf was never available in North America, I'd love to see one.   I drive the full-on EV Golf, and even the 135hp (100kW) motor is pretty zippy for city driving. 

 

Online coppice

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Re: Electric Car Experiences
« Reply #161 on: August 19, 2019, 05:29:00 pm »
Do quite like my VW Golf GTE PHEV.

For short journeys, which represent 90% of my mileage, it's fantastic.  Long term fuel economy is >200mpg (<1.2L/100km)

Thanks for the info.  The PHEV Golf was never available in North America, I'd love to see one.   I drive the full-on EV Golf, and even the 135hp (100kW) motor is pretty zippy for city driving.
You electric car guys are all torque, and that matters a lot more than maximum power for city driving. The old rubber band driven gas powered DAFs used to be able to move off the line faster than a Ferrari, because they could get quite a high gearing ratio from the transmission, and apply enormous torque for their initial burst of motion.
 

Offline boffin

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Re: Electric Car Experiences
« Reply #162 on: August 19, 2019, 05:44:59 pm »
Do quite like my VW Golf GTE PHEV.

For short journeys, which represent 90% of my mileage, it's fantastic.  Long term fuel economy is >200mpg (<1.2L/100km)

Thanks for the info.  The PHEV Golf was never available in North America, I'd love to see one.   I drive the full-on EV Golf, and even the 135hp (100kW) motor is pretty zippy for city driving.
You electric car guys are all torque, and that matters a lot more than maximum power for city driving. The old rubber band driven gas powered DAFs used to be able to move off the line faster than a Ferrari, because they could get quite a high gearing ratio from the transmission, and apply enormous torque for their initial burst of motion.

Yep, dad's old 66 Marathon was pretty quick off the line.  It had a tiny 1300cc renault engine (maybe 60hp), but was really quick off the line; although I always put reason for that on the bright yellow paint job w/ black racing stripe.

A car unknown outside of Europe.
 

Offline tom66

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Re: Electric Car Experiences
« Reply #163 on: August 19, 2019, 05:58:41 pm »
The GTE has ~400Nm of torque from standstill; more than the GTI (the GTI has to hit ~3500rpm before it can deliver that torque.)

One other thing that is rarely talked of is that without a clutch engagement, there is no need to slip that to set off quickly.  That is after all the point of launch control and like systems; with the GTE, simply press the pedal hard. Even in the sporty GTE hybrid mode, the car sets off in electric, then switches the engine on as the e-motor begins to ramp off in torque.  So, the initial launch is pretty good, though, not as crazy as the Model S, which I test drove. That really surprised me, and caught me out once on the test drive.

I find the pure electric torque to be *more* than sufficient for the majority of my driving.  The car is so quick off the line, great for nipping in gaps when you need. It's like having an ICE car that's permanently in the powerband, has full torque available until about 40 mph, which as coppice says, is basically all you ever need for a city.

For my work commute, I drive there and back on EV, and in the summer months I've been getting rated mileage so I could do the 50km or so that the car says you have in the tank.  There are chargers at work, which I need to use to make the return journey possible. But this is no issue at all, as I am usually there for 9 hours a day. Plenty of time to charge.
« Last Edit: August 19, 2019, 06:05:10 pm by tom66 »
 

Online Jeroen3

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Re: Electric Car Experiences
« Reply #164 on: August 19, 2019, 07:31:47 pm »
Do quite like my VW Golf GTE PHEV.

For short journeys, which represent 90% of my mileage, it's fantastic.  Long term fuel economy is >200mpg (<1.2L/100km)

Thanks for the info.  The PHEV Golf was never available in North America, I'd love to see one.   I drive the full-on EV Golf, and even the 135hp (100kW) motor is pretty zippy for city driving.
You electric car guys are all torque, and that matters a lot more than maximum power for city driving. The old rubber band driven gas powered DAFs used to be able to move off the line faster than a Ferrari, because they could get quite a high gearing ratio from the transmission, and apply enormous torque for their initial burst of motion.
I have a Honda CVT Hybrid, which is exactly that plus electric motor. It's quickly away, but soon overtaken. Total power to weight is miserable with only a 70 kW VTEC motor and 15 kW electric.
Would never go back to full ICE though. The immediate response on throttle and single pedal highway driving is amazing.
 

Online nctnico

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Re: Electric Car Experiences
« Reply #165 on: August 19, 2019, 07:48:21 pm »
You electric car guys are all torque, and that matters a lot more than maximum power for city driving. The old rubber band driven gas powered DAFs used to be able to move off the line faster than a Ferrari, because they could get quite a high gearing ratio from the transmission, and apply enormous torque for their initial burst of motion.
You should brush up your physics. Only power gets you moving because power delivers energy. Look at formulas and think about that long and hard before replying. Saying torque gets you going is like saying voltage is flowing through a light bulb.

But let me rephrase your comment: an EV can develop a lot of power at low revs so can get away quickly.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Online coppice

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Re: Electric Car Experiences
« Reply #166 on: August 19, 2019, 08:44:43 pm »
You electric car guys are all torque, and that matters a lot more than maximum power for city driving. The old rubber band driven gas powered DAFs used to be able to move off the line faster than a Ferrari, because they could get quite a high gearing ratio from the transmission, and apply enormous torque for their initial burst of motion.
You should brush up your physics. Only power gets you moving because power delivers energy. Look at formulas and think about that long and hard before replying. Saying torque gets you going is like saying voltage is flowing through a light bulb.

But let me rephrase your comment: an EV can develop a lot of power at low revs so can get away quickly.
I think you need to brush up your physics or your reading skills. Only the power you can actually deliver to the wheels gets you moving. Most cars cannot deliver much power from rest, because they are torque limited. They lack the extreme gearing needed to achieve the kind of torque that would allow them to deliver a high percentage of their power capacity.
 

Offline ahbushnell

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Re: Electric Car Experiences
« Reply #167 on: August 19, 2019, 11:29:03 pm »
You electric car guys are all torque, and that matters a lot more than maximum power for city driving. The old rubber band driven gas powered DAFs used to be able to move off the line faster than a Ferrari, because they could get quite a high gearing ratio from the transmission, and apply enormous torque for their initial burst of motion.
You should brush up your physics. Only power gets you moving because power delivers energy. Look at formulas and think about that long and hard before replying. Saying torque gets you going is like saying voltage is flowing through a light bulb.

But let me rephrase your comment: an EV can develop a lot of power at low revs so can get away quickly.
I think you need to brush up your physics or your reading skills. Only the power you can actually deliver to the wheels gets you moving. Most cars cannot deliver much power from rest, because they are torque limited. They lack the extreme gearing needed to achieve the kind of torque that would allow them to deliver a high percentage of their power capacity.

Let's talk physics.

For rotion the power on a shaft is:

P=omega * torque
Omega the angular velocity in rad/sec. 
torque is in N-m. 
So at zero speed there is no power. 
As the shaft begins to rotate then power comes into play.

Cars can't deliver power from rest because the speed is low or zero. 

The rate of angular acceleration is:
 
d(omega)/dt=I * torque
I is the inertia. 

This ignores friction losses. 


 
 

Online nctnico

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Re: Electric Car Experiences
« Reply #168 on: August 20, 2019, 12:10:23 am »
But in the end it is the amount of power the motor can output which determines how fast it can accellerate. Torque is only interesting for dimensioning the gears. A gearbox is just like a impedance adaption transformer. It maximises the power transfer. Also if you have a motor with a constant power output then the torque will decrease with increasing RPM. That is very counter intuitive because more is usually better.
« Last Edit: August 20, 2019, 12:12:56 am by nctnico »
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Online coppice

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Re: Electric Car Experiences
« Reply #169 on: August 20, 2019, 12:50:31 am »
But in the end it is the amount of power the motor can output which determines how fast it can accellerate. Torque is only interesting for dimensioning the gears. A gearbox is just like a impedance adaption transformer. It maximises the power transfer. Also if you have a motor with a constant power output then the torque will decrease with increasing RPM. That is very counter intuitive because more is usually better.
Read what ahbushnell wrote. When the car is moving slowly it takes a huge amount of torque for even a small amount of power to be applied to accelerating the car. Any real world motor has a maximum torque that it can produce, and this limits the power it can apply to accelerating the car, and therefore limits the acceleration. As the car speeds up, the amount of power needed to sustain maximum torque rises, until the engine becomes limited by the amount of power it can produce. From that point it is the power capacity of the motor which limits acceleration.
 

Offline EEVblog

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Re: Electric Car Experiences
« Reply #170 on: August 20, 2019, 01:23:03 am »
Does the LEAF have a 240V 10A EVSE these days?
IIRC is never used to?
If I got a LEAF I'd picture myself charging from a normal 240V 10A outlet quite a lot.
 

Offline tom66

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Re: Electric Car Experiences
« Reply #171 on: August 20, 2019, 06:21:07 am »
Yes, in the UK at least the Leaf comes with a standard "granny lead" as well as a type2 lead (the Leaf itself either has a type1 socket for older models, or type2 for newer.)
 

Offline tom66

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Re: Electric Car Experiences
« Reply #172 on: August 20, 2019, 06:25:23 am »
But in the end it is the amount of power the motor can output which determines how fast it can accellerate. Torque is only interesting for dimensioning the gears. A gearbox is just like a impedance adaption transformer. It maximises the power transfer. Also if you have a motor with a constant power output then the torque will decrease with increasing RPM. That is very counter intuitive because more is usually better.

The point isn't that EV's have more torque, the e-Golf has approximately the same torque figure as a 2.0L petrol TSI engine.

The point is that an EV can deliver the full torque to the motor shaft from zero rpm, without a clutch or torque-converter slipping to regulate speed, and without having to be at a high-rpm.  Most petrol engines deliver peak torque around 3000 rpm, which means that for first gear in a regular car, you need to be around 15 mph before the vehicle is maximising its torque capability.

One side effect of this if is you have ever tried to park a car with an automatic gearbox.  It is a lot harder in my car to park (torque control is worse so creeping into my short driveway is hard) when the EV battery is "flat" and the car is using the engine exclusively for drive functions. When in the electric mode, I can creep forward less than 1cm at a time because the clutches are fully engaged and there is no need to slip anything.

Climbing up a hill is also interesting, at low speeds.  The "power meter" in the GTE will go to about 30%, which would indicate that the car is pulling 25kW or so, but the actual power consumption is around 3-4kW. (At low speeds the power meter seems to map to torque instead, perhaps to give a consistent appearance.) Most ICE vehicles to climb a hill need to run the engine quite aggressively in a low gear to get the torque required, but my car will climb almost anything in 4th or 5th gear in E-mode, and burns relatively few electrons doing this.
« Last Edit: August 20, 2019, 06:28:33 am by tom66 »
 

Offline boffin

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Re: Electric Car Experiences
« Reply #173 on: August 20, 2019, 03:17:31 pm »
Does the LEAF have a 240V 10A EVSE these days?
IIRC is never used to?
If I got a LEAF I'd picture myself charging from a normal 240V 10A outlet quite a lot.
In North America, the couple of friends that I know that have them got 120V/12A charging cables with theirs. Whether that was the dealer that threw it in or not, I'm not sure, but a 240/10A is pretty inexpensive (Check out Mike's recent teardown of a couple).
 

Online nctnico

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Re: Electric Car Experiences
« Reply #174 on: August 20, 2019, 05:36:40 pm »
But in the end it is the amount of power the motor can output which determines how fast it can accellerate. Torque is only interesting for dimensioning the gears. A gearbox is just like a impedance adaption transformer. It maximises the power transfer. Also if you have a motor with a constant power output then the torque will decrease with increasing RPM. That is very counter intuitive because more is usually better.

The point isn't that EV's have more torque, the e-Golf has approximately the same torque figure as a 2.0L petrol TSI engine.

The point is that an EV can deliver the full torque to the motor shaft from zero rpm, without a clutch or torque-converter slipping to regulate speed, and without having to be at a high-rpm.  Most petrol engines deliver peak torque around 3000 rpm, which means that for first gear in a regular car, you need to be around 15 mph before the vehicle is maximising its torque capability.

One side effect of this if is you have ever tried to park a car with an automatic gearbox.  It is a lot harder in my car to park (torque control is worse so creeping into my short driveway is hard) when the EV battery is "flat" and the car is using the engine exclusively for drive functions. When in the electric mode, I can creep forward less than 1cm at a time because the clutches are fully engaged and there is no need to slip anything.

Climbing up a hill is also interesting, at low speeds.  The "power meter" in the GTE will go to about 30%, which would indicate that the car is pulling 25kW or so, but the actual power consumption is around 3-4kW. (At low speeds the power meter seems to map to torque instead, perhaps to give a consistent appearance.) Most ICE vehicles to climb a hill need to run the engine quite aggressively in a low gear to get the torque required, but my car will climb almost anything in 4th or 5th gear in E-mode, and burns relatively few electrons doing this.
Sorry but this is utter nonsense from a physics point of view. It doesn't make any sense at all.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 


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