EV Discussion thread

Petriix

Ultimately people need to get away from the notion that an EV has a specific 'range'; they don't. They have a specific amount of usable energy which can be utilised to propel the vehicle (overcoming variable external forces such as air resistance, displacing water etc) and run ancillary systems (particularly heating). It's also worth understanding that batteries cannot release as much of their stored energy when cold.

The WLTP 'range' is simply a basis for comparison rather than a real world expectation. There isn't a 'shortfall' in winter. Just like driving faster or in heavy rain, winter driving typically uses more energy for things other than propelling the vehicle. 

Martyn1981

Petriix said:

Ultimately people need to get away from the notion that an EV has a specific 'range'; they don't. They have a specific amount of usable energy which can be utilised to propel the vehicle (overcoming variable external forces such as air resistance, displacing water etc) and run ancillary systems (particularly heating). It's also worth understanding that batteries cannot release as much of their stored energy when cold.

The WLTP 'range' is simply a basis for comparison rather than a real world expectation. There isn't a 'shortfall' in winter. Just like driving faster or in heavy rain, winter driving typically uses more energy for things other than propelling the vehicle. 

Very true. The worst I've seen was in December last year, not too cold, but constant heavy rain, with standing water everywhere. Was averaging only a little better than 400Wh/mile. Wouldn't have appreciated the extra work if driving an ICE. Return journey was about 300Wh, seemed just as bad, but perhaps the standing water was a bit better, and/or the wind was having an affect.

Actually, I take that back, worst economy would be first gen Leaf. Coming back from friends with a full charge I knew I could push it a bit harder, so 70mph on motorway and heating on for a 50 mile journey, got home with 5 miles to spare, so for a 24kWh battery, 92% SOH (according to Leafspy), I make that ~400Wh/mile. Probably wouldn't have made it home if it had rained!

JKenH

Petriix said:

Ultimately people need to get away from the notion that an EV has a specific 'range'; they don't. 

While that may very well be true, it isn’t a great argument to sell EVs to those teetering on the brink of a purchase. 

Edit: deleted most of first and whole of second paragraph of the quoted post from @Petriix as my comment related to the first sentence only.

JKenH

WLTP figures tend to be more optimistic for BEVs than ICEVs based on these findings reported by Fleet News.

https://www.fleetnews.co.uk/news/latest-fleet-news/electric-fleet-news/2021/07/29/evs-fall-short-of-wltp-range-by-15

https://www.fleetnews.co.uk/news/manufacturer-news/2020/06/18/new-cars-are-54-less-efficient-than-wltp-figures-suggest-says-what-car

My personal experience is that it is far easier to better the WLTP consumption in a petrol engined car than it is to beat the WLTP range of an EV. That may be due to the nature of the journeys I do. If I spent most of my time commuting then it might be a different story. But therein lies part of the problem. 

The WLTP test, because it attempts to simulate a range of differing driving environments in a short period, is biased in favour of short journeys and a relatively low average speed which favour EVs compared to ICEVs. The WLTP range is then extrapolated from the WLTP consumption. The average speed in the WLTP cycle is low, just 46kph, I believe. Around town and commuting (i.e. local trips) you may get close to the WLTP range but range is of little or no consequence in these scenarios as you can charge up at home long before range becomes an issue. 

On long trips however, speeds are going to be higher and sustained for longer periods. These conditions favour ICEvs but are not fully reflected in the WLTP test. The EV is then outside the environment where it performs the best and may well fall short of its WLTP consumption and hence it is less likely to achieve its WLTP range. This then leads to reports that EVs don’t match their WLTP range. 

The WLTP range is never intended to demonstrate real world range - it is a construct calculated from the average consumption over the WLTP cycle x the usable capacity of the battery. 

A second issue is that the WLTP test is carried out at 23 Centigrade, which is virtually optimal for EVs. It should be no surprise that EVs therefore fall significantly short of their WLTP range in cold weather. 

The only way to avoid theses stories is to quote an urban range and a motorway range based on a higher speed and base the test at a lower temperature. The results won’t be so flattering for EVs but they will be more helpful to the consumer. 

Edit: correct link added

michaels

Martyn1981 said:

Petriix said:

Ultimately people need to get away from the notion that an EV has a specific 'range'; they don't. They have a specific amount of usable energy which can be utilised to propel the vehicle (overcoming variable external forces such as air resistance, displacing water etc) and run ancillary systems (particularly heating). It's also worth understanding that batteries cannot release as much of their stored energy when cold.

The WLTP 'range' is simply a basis for comparison rather than a real world expectation. There isn't a 'shortfall' in winter. Just like driving faster or in heavy rain, winter driving typically uses more energy for things other than propelling the vehicle. 

Very true. The worst I've seen was in December last year, not too cold, but constant heavy rain, with standing water everywhere. Was averaging only a little better than 400Wh/mile. Wouldn't have appreciated the extra work if driving an ICE. Return journey was about 300Wh, seemed just as bad, but perhaps the standing water was a bit better, and/or the wind was having an affect.

Actually, I take that back, worst economy would be first gen Leaf. Coming back from friends with a full charge I knew I could push it a bit harder, so 70mph on motorway and heating on for a 50 mile journey, got home with 5 miles to spare, so for a 24kWh battery, 92% SOH (according to Leafspy), I make that ~400Wh/mile. Probably wouldn't have made it home if it had rained!

Usable on the 24 leaf was only 21kwh.  Against that the speedo under-reads by 10%

JKenH

michaels said:

Martyn1981 said:

Petriix said:

Ultimately people need to get away from the notion that an EV has a specific 'range'; they don't. They have a specific amount of usable energy which can be utilised to propel the vehicle (overcoming variable external forces such as air resistance, displacing water etc) and run ancillary systems (particularly heating). It's also worth understanding that batteries cannot release as much of their stored energy when cold.

The WLTP 'range' is simply a basis for comparison rather than a real world expectation. There isn't a 'shortfall' in winter. Just like driving faster or in heavy rain, winter driving typically uses more energy for things other than propelling the vehicle. 

Very true. The worst I've seen was in December last year, not too cold, but constant heavy rain, with standing water everywhere. Was averaging only a little better than 400Wh/mile. Wouldn't have appreciated the extra work if driving an ICE. Return journey was about 300Wh, seemed just as bad, but perhaps the standing water was a bit better, and/or the wind was having an affect.

Actually, I take that back, worst economy would be first gen Leaf. Coming back from friends with a full charge I knew I could push it a bit harder, so 70mph on motorway and heating on for a 50 mile journey, got home with 5 miles to spare, so for a 24kWh battery, 92% SOH (according to Leafspy), I make that ~400Wh/mile. Probably wouldn't have made it home if it had rained!

Usable on the 24 leaf was only 21kwh.  Against that the speedo under-reads by 10%

I found my 30kWh Leaf speedo over read and the odometer overread  slightly. The 40kWh was far more accurate. 

Grumpy_chap

Petriix said:

Ultimately people need to get away from the notion that an EV has a specific 'range'; they don't. They have a specific amount of usable energy which can be utilised to propel the vehicle (overcoming variable external forces such as air resistance, displacing water etc) and run ancillary systems (particularly heating). It's also worth understanding that batteries cannot release as much of their stored energy when cold.

The WLTP 'range' is simply a basis for comparison rather than a real world expectation. There isn't a 'shortfall' in winter. Just like driving faster or in heavy rain, winter driving typically uses more energy for things other than propelling the vehicle. 

This is true, so far as it goes, but honest discussion is needed to avoid the unsatisfied EV customer.

There is a big gap of understanding amongst many. 

It is widely understood that the quoted mpg for an ICE is an indication for comparison.  Very few people expect to achieve the quoted figure, or even close.  Very few car sales representatives would say that the quoted figure can be achieved in the real world.  There is very limited practical impact in the use of the vehicle from this difference.  There is a cost impact to the use of the vehicle from this difference.

With an EV, it does not seem to be so widely known that the WLTP figure is equivalent to the quoted mpg for an ICE.  There is a high proportion of people that truly expect to achieve the quoted range, or very close.  Car sales representatives will sell the range as achievable.  Reduced range has a far more significant real world practical impact than simply lower mpg / the higher energy consumption.  Finally, but it is not often talked about, the reduced range has an impact to the energy costs for the use of the vehicle.

Denying the "shortfall" in winter seems like optimistic choice of language.  There is some impact in energy consumption arising from wind, rain, heating etc.  That delta is quote small as I understand it in the context of total energy demand to propel the vehicle forwards at a given speed.  It has a cost impact and range impact.  However, the reduced operating capacity of the battery in cold conditions is far greater and has far more impact to the practical use of the vehicle.  It cannot be denied.  It is the equivalent of putting a pillow in the tank of an ICE.

Members of the pro-EV community need to be honest and acknowledge the weaknesses.  Failure to do so will result in misleading expectations and ultimately delay the overall conversion from ICE to EV.

Martyn1981

michaels said:

Martyn1981 said:

Petriix said:

Ultimately people need to get away from the notion that an EV has a specific 'range'; they don't. They have a specific amount of usable energy which can be utilised to propel the vehicle (overcoming variable external forces such as air resistance, displacing water etc) and run ancillary systems (particularly heating). It's also worth understanding that batteries cannot release as much of their stored energy when cold.

The WLTP 'range' is simply a basis for comparison rather than a real world expectation. There isn't a 'shortfall' in winter. Just like driving faster or in heavy rain, winter driving typically uses more energy for things other than propelling the vehicle. 

Very true. The worst I've seen was in December last year, not too cold, but constant heavy rain, with standing water everywhere. Was averaging only a little better than 400Wh/mile. Wouldn't have appreciated the extra work if driving an ICE. Return journey was about 300Wh, seemed just as bad, but perhaps the standing water was a bit better, and/or the wind was having an affect.

Actually, I take that back, worst economy would be first gen Leaf. Coming back from friends with a full charge I knew I could push it a bit harder, so 70mph on motorway and heating on for a 50 mile journey, got home with 5 miles to spare, so for a 24kWh battery, 92% SOH (according to Leafspy), I make that ~400Wh/mile. Probably wouldn't have made it home if it had rained!

Usable on the 24 leaf was only 21kwh.  Against that the speedo under-reads by 10%

According to sat nav the speedo over read quite a bit, 70 on the dial was low to mid 60's. Most seem to be over by ~5%, I've always assumed that it makes tem look faster, and less likely to get a lawsuit if you are booked for speeding. Tesla is pretty close, so need to be a bit more careful.

Grumpy_chap

Martyn1981 said:

According to sat nav the speedo over read quite a bit, 70 on the dial was low to mid 60's. Most seem to be over by ~5%, I've always assumed that it makes tem look faster, and less likely to get a lawsuit if you are booked for speeding. Tesla is pretty close, so need to be a bit more careful.

Speedo's always over-read.
On our car, 75 mph indicated is 70 mph sat nav.
Speedo's are not allowed to under-read:
"The regulation states that speedometers must never underreport a vehicle's speed, while it must never overreport by more than 110% of the actual speed + 6.25mph."
https://www.startrescue.co.uk/breakdown-cover/motoring-advice/safety-and-security/how-accurate-is-my-speedometer#

JKenH

Grumpy_chap said:

Petriix said:

Ultimately people need to get away from the notion that an EV has a specific 'range'; they don't. They have a specific amount of usable energy which can be utilised to propel the vehicle (overcoming variable external forces such as air resistance, displacing water etc) and run ancillary systems (particularly heating). It's also worth understanding that batteries cannot release as much of their stored energy when cold.

The WLTP 'range' is simply a basis for comparison rather than a real world expectation. There isn't a 'shortfall' in winter. Just like driving faster or in heavy rain, winter driving typically uses more energy for things other than propelling the vehicle. 

This is true, so far as it goes, but honest discussion is needed to avoid the unsatisfied EV customer.

There is a big gap of understanding amongst many. 

It is widely understood that the quoted mpg for an ICE is an indication for comparison.  Very few people expect to achieve the quoted figure, or even close.  Very few car sales representatives would say that the quoted figure can be achieved in the real world.  There is very limited practical impact in the use of the vehicle from this difference.  There is a cost impact to the use of the vehicle from this difference.

With an EV, it does not seem to be so widely known that the WLTP figure is equivalent to the quoted mpg for an ICE.  There is a high proportion of people that truly expect to achieve the quoted range, or very close.  Car sales representatives will sell the range as achievable.  Reduced range has a far more significant real world practical impact than simply lower mpg / the higher energy consumption.  Finally, but it is not often talked about, the reduced range has an impact to the energy costs for the use of the vehicle.

Denying the "shortfall" in winter seems like optimistic choice of language.  There is some impact in energy consumption arising from wind, rain, heating etc.  That delta is quote small as I understand it in the context of total energy demand to propel the vehicle forwards at a given speed.  It has a cost impact and range impact.  However, the reduced operating capacity of the battery in cold conditions is far greater and has far more impact to the practical use of the vehicle.  It cannot be denied.  It is the equivalent of putting a pillow in the tank of an ICE.

Members of the pro-EV community need to be honest and acknowledge the weaknesses.  Failure to do so will result in misleading expectations and ultimately delay the overall conversion from ICE to EV.

Yes, this is a valid point. Many  forumites and even journalists put the emphasis on cabin heating as a reason EVs are less efficient in winter. That is wrong. While using the heater will reduce range the dramatic reductions in range we see in very cold weather are down to the internal resistance of the battery. 

My son explained it to me as follows

All batteries have internal resistance, which is why they get hotter the more power you put through them (in or out). The internal resistance increases as the battery gets colder. Therefore, for a given level of driving power a cold battery will absorb more energy overcoming its internal resistance, which will make the kWh/ mile worse for the cold battery. This will also heat up the battery as you drive, so the efficiency will then improve.

It is easiest to see this in the Leaf which has no thermal battery management. In winter the efficiency will start off very low. For the first couple of miles it can be sub 2mpk then it will gradually creep up. On a trip to Wales in November 2021 I drove about 30 miles without any heating on before it crept over 3mpk. I then put the heating on and the efficiency continued improving eventually reached the high 3s.