EV Discussion thread

JKenH

Martyn1981 said:

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.

Very similar to my 30kWh. I reckon it was about 10% over. Odometer was about 2% over. It is exactly 100 miles to my son’s house according to Google Maps and the 40kWh Leaf but 102 miles in the 30kWh Leaf. 

1961Nick

JKenH said:

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. 

Pre-heating the Tesla battery while it was plugged into the charger made a big difference in December when it was -8C. I didn't record any figures, but it was clear that the energy saved while driving with a preheated battery was a lot more than the energy invested in heating it.

michaels

Thanks all, I did if course mean over read. 70 indicated on our 24 is 63 according to the Sat nav

Petriix

I don't think it's helpful to talk in binary terms like winter/summer etc. When it's colder you lose more energy to various factors. Different battery chemistries respond differently to the cold. My NCM battery is far more efficient at 0 degrees than the LFP equivalent in the more recent MG5, for example.

Cabin heating becomes a significant factor when doing lots of short journeys with gaps between or when sitting in the car waiting for classes to finish. The good news is that, after the initial warm-up, longer journeys become more efficient. If you rapid charge en route then you typically get a big jump in efficiency from the extra heat in the battery.

The other piece of good news is that people typically don't use their full battery capacity very often. 'Range' is mostly moot when considered within the most common driving paradigms. [I know that many people do drive long distances regularly, but they are very much in the minority.]

When people ask me about my EV's range I tend to give an honest and nuanced answer like: "I average about 200 miles per full charge (except I never actually go from 100% to 0%) but it could be as low as 100 miles or as much as 300 miles in extreme circumstances. Ultimately it's not something I worry about because 99% of my journeys are well within range of home". 

Martyn1981

Yes, I was thinking the same, for longer journeys, cold and heat level off somewhat, plus you cn of course compensate to some degree by driving a bit slower if you have concerns about charger availability.

For lots of short journeys it's a shame to get less efficiency (same for an ICEV), but less important.

Hopefully as the public charger network improves, fears will subside a bit. Whilst not good news for non-Tesla's, the SC network removes any fear anxiety, and (dare I say) a need to drive as efficiently.

Still early days, and lots of changes, then polishing needed, but a truly great transition to a better product .... eventually.

Martyn1981

michaels said:

Thanks all, I did if course mean over read. 70 indicated on our 24 is 63 according to the Sat nav

Cool, fits in with what I saw, one of the most 'enthusiastic' speedo's I've encountered. When I said 70mph, that was according to the sat-nav, I believe the speedo was showing about 77.

Have to say that those 'mind your speed' signs are pretty accurate when displaying your speed. They would read a lower figure than the speedo's, but as mentioned, with the Tesla's they seem very close, so a speed camera on a steep uphill by my house used to be taken at 33, but now only 30. But of course the beauty of BEV's means easy hill climbing anyway - in the small engined ICEV's of my past, that hill/main road required shifting down to 3rd. Fun times.

Grumpy_chap

We went out today to look at the MG EV's. 

Initially, I expected to like the MG4.  While the external styling is really rather funky, I found the internal design not really to my taste.

Then we saw the MG ZS EV.  I am not a big fan of SUV style cars, but the interior for this was the best of the range.  However, there is a very long waiting list for the Long Range versions to such an extent that MG are not currently accepting orders, so that was the end of that discussion.

Finally, the MG5 which was really quite good and would be the one of the three models that we'd buy.  It was easy, but entirely uninvolving to drive, but at least Mrs G-C would also drive it (she is not keen on auto).  Well equipped (though front parking sensors were omitted for some reason), quite comfortable, perfectly functional, but possibly a bit dull.  Did, of course, try the famed EV thing on fast pull-away but the tyres / traction control system could not cope with it - when that was avoided, this was definitely the fastest thing off the mark I've ever driven.  It was anything but sporty though and there were clear signs of the budget position.  (I actually don't think the £30k price point really reflects budget, though.)

Very impressed but we then got back into Mrs G-C's Fiesta and immediately commented how that was such a higher quality feel.

Next stop was the VW / Skoda dealer along the road.  The Enyaq's were far better quality than the MG, but at an absurd price point.  Then we looked at the iD3, which was offered to match the price-point of the MG5, but as well as the budget factor being ever-so apparent (perhaps even more so than the MG), the iD3 was so strongly "greenwashing" that is was off-putting.  I had no desire to test drive the iD3 when sitting in there and after the MG models we saw earlier.  The price comparable ICEs from Skoda were far better quality.

There was a lot I really liked about the MG5 and I think it would work for us as a car, but the price-point compared to what the same budget (or less) could get as an ICE is a challenge.
Plus, on top of buying the EV, I am going to need to find another £1k or so to get a home charger installed.
I can't quite get myself to reach for the cheque book...

JKenH

Grumpy_chap said:

We went out today to look at the MG EV's. 

Initially, I expected to like the MG4.  While the external styling is really rather funky, I found the internal design not really to my taste.

Then we saw the MG ZS EV.  I am not a big fan of SUV style cars, but the interior for this was the best of the range.  However, there is a very long waiting list for the Long Range versions to such an extent that MG are not currently accepting orders, so that was the end of that discussion.

Finally, the MG5 which was really quite good and would be the one of the three models that we'd buy.  It was easy, but entirely uninvolving to drive, but at least Mrs G-C would also drive it (she is not keen on auto).  Well equipped (though front parking sensors were omitted for some reason), quite comfortable, perfectly functional, but possibly a bit dull.  Did, of course, try the famed EV thing on fast pull-away but the tyres / traction control system could not cope with it - when that was avoided, this was definitely the fastest thing off the mark I've ever driven.  It was anything but sporty though and there were clear signs of the budget position.  (I actually don't think the £30k price point really reflects budget, though.)

Very impressed but we then got back into Mrs G-C's Fiesta and immediately commented how that was such a higher quality feel.

Next stop was the VW / Skoda dealer along the road.  The Enyaq's were far better quality than the MG, but at an absurd price point.  Then we looked at the iD3, which was offered to match the price-point of the MG5, but as well as the budget factor being ever-so apparent (perhaps even more so than the MG), the iD3 was so strongly "greenwashing" that is was off-putting.  I had no desire to test drive the iD3 when sitting in there and after the MG models we saw earlier.  The price comparable ICEs from Skoda were far better quality.

There was a lot I really liked about the MG5 and I think it would work for us as a car, but the price-point compared to what the same budget (or less) could get as an ICE is a challenge.
Plus, on top of buying the EV, I am going to need to find another £1k or so to get a home charger installed.
I can't quite get myself to reach for the cheque book...

You are trying to rationalise buying an EV when rationally buying one does not make any sense to you. You want an EV, fair enough, but you may need to ascribe some value to the reasons you want one. 

I have had numerous sports cars in my life but rationally they didn’t make sense - unless I put a value on the intangible benefits of owning one. 

Grumpy_chap

JKenH said:

You are trying to rationalise buying an EV when rationally buying one does not make any sense to you. 

I am an Engineer - everything is rational and logical decision making and there is no other way

JKenH

BMW iX sudden unintended acceleration

I came across a newspaper report on the Facebook EV Drivers thread of an incident where a BMW iX when approaching a sharp corner had suddenly accelerated away from 15mph causing the driver to lose control and crash. The photo of the article on Facebook was poor and I couldn’t find another report on line but in searching I came across this thread.

https://www.ixforums.com/threads/b-mode-random-acceleration.953/page-3

I believe many cars have the speed limit assist function which when on cruise control can cause a car to accelerate up to the speed limit. Possibly the BMW is misreading 30mph signs as 80. I don’t see why the problem should be confined to EVs but the acceleration in an EV can be much more rapid so the potential for a driver to believe the car is out of their control is greater. If you are on ACC and the road clears in front it could potentially cause you to accelerate suddenly as the car in front goes round a sharp corner. If you are at low speed in a high gear in a 1.0 litre petrol car not a lot happens when the road clears but if you suddenly apply over 600Nm of torque it might be a different story. 

SUA used to be regarded as a Tesla issue but as more EVs hit the road will we see more of these reports for other cars?