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As I've said before, my wife currently commutes to a place 13 miles away. Doing it in an EV saves us about £80/mo versus the cost of diesel. The issue for us is that we really should have only one car, but we cannot otherwise tow the caravan. But then, we don't go away that often currently so it's looking like an expensive way to get a holiday.
Anyone got an iX40? I'm currently driving one while my Mercedes is being repaired and I can't seem to get it over 2.7 miles per kilowatt.
Queueing in an ICE car is worthwhile as it's maybe 2 minutes per car, but charging an EV might take 30 minutes, so most people would move on unless they were really low (I usually plan to charge early, so that I can move on). I hadn't thought about the charger owner having to rent the space; many chargers have 2 cables and say "dual charging possible", but only one space. I put my car in the adjacent parent & child space, as the cable was long enough and none of the other p & c spaces were in use. I found a snag with dual charging when the guy using the other cable didn't spot how to switch the display over and disconnected my charge. I found I had to unplug and restart from scratch.
I can’t seem to get it over 2.7 miles per kilowatt.
That's about what Drac was getting from his big Audi, not sure if BMWs are similarly afflicted with low economy.
What kind of driving?
doomanic looking at the specs it seems to have a usable 71 kWh battery and projected range of 220 miles giving an absolutely terrible efficiency of 3.1 miles per kWh - so actual of 2.7 doesn’t sound surprising but no idea how BMW managed to make it so inefficient.
I usually plan to charge early, so that I can move on
Yeah. I did a trip that needed about 110% of charge, so I needed to add a bit of charge at some point, but it didn't really matter where I added it other than it took slightly less time if I ran the battery lower.
doomanic looking at the specs it seems to have a usable 71 kWh battery and projected range of 220 miles giving an absolutely terrible efficiency of 3.1 miles per kWh – so actual of 2.7 doesn’t sound surprising but no idea how BMW managed to make it so inefficient.
It's the size of a house and weighs more than Nadine's liquor cabinet. It's also pretty rapid if you hoof it with 326hp.
What kind of driving?
Mixed, mostly town driving in moderate to no traffic but a couple of trips that included NSL dual carriageways. I've been driving it what I consider to be an economical manner for the most part but I took a friend out for a spin today so obviously had to hoof it a couple of times (I'm not including today's driving in my considerations).
A £70K+ car is well out of my price range (in fact there isn't a new EV I can afford currently, I tried to buy an MG 4 on the work salary sacrifice but I don't earn enough... 😢) but these economy figures mean my annual Golfy trip would be cheaper in my Merc!
It’s the size of a house and weighs more than Nadine’s liquor cabinet
It also looks like it was designed by me, when I was 5
I’ve been driving it what I consider to be an economical manner for the most part
What constitutes economical driving in an EV is not the same as an ICE. In an ICE if you boot it, lots of your burning fuel comes flying out of the exhaust so your efficiency drops. In an EV however, in my experience booting it makes very little difference. The main factor seems to be the actual speed you're driving at. In an ICE town driving is the worst because you're in lower gears and you're accelerating all the time, but constant A road driving is better despite having 4x the air resistance to deal with. However n an EV town driving is the most efficient, despite the accelerating. And you recover some of that energy (but not all).
but these economy figures mean my annual Golfy trip would be cheaper in my Merc!
Yeah, even with our super efficient Ioniq and no public charging subscription, charging away from home was about the same cost as my somewhat more frugal Merc. However, with home charging it was a tenth the cost.
I don’t know if it’s a BMW thing , and I’ve mentioned it before, but my iX3 is far more efficient on a 60-70mph run than it is around town
Synchronous AC electric motors do have an efficiency curve, so at very low speeds they do get worse. And the energy cost of running the inverter, the electronics and the HVAC are fixed per minute not per mile, so efficiency in heavy crawling traffic was worse for us but in the worst jams it only went down to about the same as a motorway trip on a cold day. Maybe there is a BMW difference I dunno.
Motor efficiency vs speed and vs load is a thing, but it’s a fairly small factor.
The three things that dominate the game efficiency vs speed curve for both ICE are the “per time” losses - energy to heat or cool the cabin and in an ICE just to keep the engine running, and the frictional and aero losses and efficiency vs load curve of the power source.
ICEs are quite (very) poor efficiency at low loads. There is a minimum level of energy expenditure which is mostly lost to heat at low loads. EVs are fairly flat vs loadZ
Add to the above the fact that EVs (and hybrids) can recoup braking energy* and the peak efficiency for an EV is pretty low - 20mph ish. For an ICE it’s quite a bit higher - 50 ish.
On country road type driving my i4 recoups around 25% of total energy spend according to the trip computer. Obviously that changes with terrain and type of road. Flat motorways would be close to zero. Hilly terrain or city driving is probably higher.
Just talking efficiency... what should I/we expect re. charging efficiency?
We bought a 2nd hand eNiro a few weeks ago and I'm just looking at what it's costing to charge on public charge points recently.
I understand the eNiro has a 64kWh usable battery.
Last weekend I charged from (I think) around 16% to 80% so ~ 41kWh needed to fill the battery. The CPS history shows 47.4kWh drawn in 82 minutes, 87% charge efficiency.
Just now (going on a long journey tonight) I've charged it to 99%. I think it was sitting at 77% when I plugged it in so 22% or ~14kWh. CPS shows 19.7kWh drawn in 94 minutes, 71% efficiency.
I'm not sure on these numbers, I'll pay more attention next time. But if these are anywhere near correct this seems pretty bad. From reading I did before buying I was expecting 90%+ charging efficiency.
It seems like current charge level is having a huge effect on charging efficiency (really best not to charge > 80% if at all possible?). How does charging rate affect efficiency?
While I've found lots of resources for different cars and driving efficiency there seems to be a complete dearth of data on charging efficiency. It seems from these numbers that charging efficiency could be more relevant than driving efficiency (or at least may have a significant impact on overall efficiency).
Just a quick interlude back to the hybrid....
It seems to be wearing in/we are getting accustomed. Mrs K did a 70 mile round trip with her and the two kids, and 2 bikes on a Thule tow bar rack last night. The way out was 3 miles in/out N London, 10 miles dual carriageway of which the way out was congested for the first third, and the rest B roads through Essex. The return journey was 5 miles B road to the M11, 27 miles M11/M23 and 3 miles back into N London.
The result - 50MPG on the nose. She is ambivalent to car stuff, so in her words she " just drove it". So no skewed hyper-miling 😀
@zntrx I have a feeling that charging efficiency is affected by how full the battery is with lower efficiency at the top end.
as the battery reaches its maximum capacity, heat can increase, reducing the efficiency of the charge.
We've had our iX1 for a few weeks now. It is very nice.
I have a feeling that charging efficiency is affected by how full the battery is with lower efficiency at the top end.
I think that's true of all lithium ion batteries.
@ZNTRX Interesting - I took a quick look at a few recent charging sessions on my i4. A bit of a pain to drag out data from the apps so I just did a few.
7kW Charger
22-45% charge
Charger (podpoint) showed 18.6kW.hr
Car (BMW i4 app) showed 18.8kW.hr
% differences * battery size = 18.56
Charge efficiency = 98.7-99.8%
7kW Charger
45-92% charge
Charger (podpoint) showed 40.9kW.hr
Car (BMW i4 app) showed 40kW.hr
% differences * battery size = 34.93
Efficiency = 92.7-94.8
Fast charger
6-90% charge
Charger (IONITY) showed 72.5kW.hr
Car (BMW i4 app) showed 72kW.hr
% differences * battery size = 67.79
Efficiency = 93.5-93.8
It looks like the BMW app is either charge taken rather than delivered to the battery.
Charging efficiency looks overall very good. >93% in all cases.
7kW charger at up to 45% was close to 100%, dropping to 93-95 when charged to full.
The fast charger was similar - 94% efficient.
I'd imagine that fast charging is less efficient, due to heat generation which has got to go somewhere - when fast charging I think that the battery back is being actively cooled at higher SOC, so that's energy lost.
@zntrx - those numbers don't look so great. For your charge to 99% indicated an average loss of 4.4kW. That might align with a cooler running on full to cool the battery pack down maybe? Could be just inaccurate input data. Maybe try checking a few sessions with a few different chargers etc to be sure.
Oh yeah - the power to cool or heat the battery to optimum temps comes from the charger which charges you for it. I have read about that.
Yep. Given that all power in an EV ultimately comes from the charger then yes, this is true.
Same applies to power used to pre-heat the car and battery before setting off if you do that. Even if not plugged in it comes from the battery which is then later replenished by charging.
Saw the new EV Escalade in the news today. I guess for local air quality it's better than a big old V8 chugging away, but jeez, the sheer heft of the thing!
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I naively hoped manufacturers would try lightening and improving aerodynamics for range on these things, but nope, just chuck a 200KWH battery in there- job done.
@Multi21. Yeah, me too. It feels like an arms race where through education and infrastructure we should be going towards lighter smaller battery cars with focus on miles per kw. And don't get me started on "ludicrous mode"! 🙂
this thing about not charging to 100% - surely the car is smart enough to work out it's own battery protection, and stop a bit short and report that figure as '100%' ?
I have only charged my i4 once so far, at home, as only had it a week and a bit. I plugged it in around 8pm and the Easee App told me it would stop at around 3am, which it did, with the display showing it at 100%.
this thing about not charging to 100% – surely the car is smart enough to work out it’s own battery protection, and stop a bit short and report that figure as ‘100%’ ?
That's exactly what they do.
And don’t get me started on “ludicrous mode”!
Whilst yes I agree with your disapproval, by making their cars really fast Tesla made EVs credible and desirable. You didn't hear milk-float gags after that, did you? Once they were desirable, they were seen as the future and other manufacturers had to catch up. And here we are.
That’s exactly what they do.
ah, that's good then. I shall not give it another thought 🙂
EV Escalade
Looks like someone's going after the US Range Rover market there
revs1972
Looks like someone’s going after the US Range Rover market there
These things make a Range Rover look like a toy car
(note, that's the old LWB model as the sites not updated yet, but it looks about right size-wise. 19ft long for example).
this thing about not charging to 100% – surely the car is smart enough to work out it’s own battery protection, and stop a bit short and report that figure as ‘100%’ ?
The car doesn't know how far you want to drive next, so can't work it all out. If you're going to need all the battery, charge it 100% just before you leave, or a close to that as you reasonably can. If you're not going need 100%, charge it to 80%. That's if you want to maximise the battery life.
What the car reports as 100% is the declared capacity. When new, it probably has 10% more that it never uses, but the battery life is "guaranteed" for 3/5/8 years, and that cushion is to enable it to still provide the nominal capacity at the end of guarantee period.
@molgrips. Yeah, you are right, there's no denying Tesla had that impact, I just kind of wish the public took to EVs based on what the Leaf had introduced but I guess that's the old man in me and my own person interests.
villageidiotdan
Free Member@molgrips. Yeah, you are right, there’s no denying Tesla had that impact, I just kind of wish the public took to EVs based on what the Leaf had introduced but I guess that’s the old man in me and my own person interests.
Yes or carried on with the i3's direction. Shame.
The Tesla direction seems quite good to me. Yes they’re silly fast but unlike ICEs that doesn’t have to come with a major drop in efficiency. They’re light for what they are and designed with low drag and maximum useable passenger space inside.
Are they going to make a city Tesla I wonder? Along the lines of the BMW i3 sort of thing. Maybe a scaled down, squashed M3z. Hopefully actually styles to suit its new proportions this time unlike the model Y.
That's a positive perspective - much as I dislike the character the Tesla is surprisingly efficient in the miles per kw stakes, and a proper 4 door car. If they could go in the city car direction (dear god why do I keep looking longingly at the Citroen Ami!?!) and improve on the efficiency even more that would be amazing. Oh, and drop Musk/cybertruck
I just kind of wish the public took to EVs based on what the Leaf had introduced
I think we have. Not many super fast EVs in the road here, just people getting around. As said, there's no real 9enalty to making an EV really fast. It doesn't mean it's less efficient, unlike an ICE, so why not give it 250 or 300bhp?
There seems to be no real down side to my Tesla being stupidly fast other than the insurance group. I rarely use the acceleration but it’s nice to know you can nip past things quickly when you need to.
Miles per kWh is better than our other EV which is half the size.
What’s wrong with them being a bit cool and fast as well as green? There seems to be a lot of Tesla bashing around but they led the way in making EVs commonplace and there are still very few if any EVs that are more efficient.
I do like the Model 3. If it had been a hatchback instead of a saloon design it would have been right at the top of my list (my car spends too much time with back seat down and a bike in the back, or full of camping gear etc to be able to compromise).
The BMW i4 and Polestar 2 do the car (not SUV) shaped hatchback thing quite well. Neither as good an “electric” car as the M3 though - less efficient etc and both the i4 is really compromised in the back because of its long bonnet / coupe style roofline. That’s partly because it shares an ICE platform but also because BMW are going after the “I like it because it still looks like a beemer” market (which is one of the reasons I chose it- never had a Beemer before but always secretly wanted one).
Fingers crossed this all converges a bit and newer generations of car blend all of the desirable features together to give some sensible options, like the ICE market had done. Oh hang on, they’re all gone towards jacked up SUV style things too, dammit. Fingers crossed that far passes.
The insurance group and tyre replacement cost featured in the buying process of the Corsa e. Tyres seemed a reasonable cost and there were a few options in the event of a damaged tyre that needed replacing, sub £100 each. I did consider a BMW i3 but the tyre options seemed to be limited to 1 tyre at £250 each.
The insurance on the Corsa e is higher than the Picanto it replaced but only by around £100 and considering the cost and performance difference between the 2 cars it was an acceptable increase.
Weve just ordered an MG4 - the first affordable car with good range. I think the industry will have to respond to that.
A week and a bit of i4 use and no negatives. It is very easy and relaxing to drive, a very comfy place to be. Performance is silly if wanted and interior and boot space pretty good. It does 4 miles/kw on average so far and that’s with climate on all the time. Our teenage sons are both 6’2” and find the back seats and headroom ok, heads quite clear of roof.
Charging at home is working out a little more than half the price for same use compared to previous diesel Q5.
^^ 👍👌
molgrips
I think we have. Not many super fast EVs in the road here, just people getting around. As said, there’s no real 9enalty to making an EV really fast. It doesn’t mean it’s less efficient, unlike an ICE, so why not give it 250 or 300bhp?
There is a small penalty, compare a Model 3 LR to a Model 3 Performance. Same size battery, 10% less range. To be honest, the LR is quick enough anyhow, full bore acceleration in the Performance made me feel travel sick!
What’s wrong with them being a bit cool and fast as well as green? There seems to be a lot of Tesla bashing around but they led the way in making EVs commonplace and there are still very few if any EVs that are more efficient.
+1 I used to think that without Tesla EVs would be 5 years behind where they are now. I now realise I was wrong they would be 10 years behind. Tesla have shown desirable EVs can be built at scale for a nice profit and, combined with an effective charging network, are a practical proposition. They have, with some help from the Chinese, dragged legacy auto, kicking and screaming, into EVs.
There is a small penalty, compare a Model 3 LR to a Model 3 Performance. Same size battery, 10% less range.
Does it come with bigger wheels? There shouldn't be any other penalty, except perhaps more friction if the performance one has two motors?
Charging at home is working out a little more than half the price for same use compared to previous diesel Q5.
I assume you haven't got an EV tariff?
There is a version with a single motor vs the performance two. There’s also a twin motor non performance one (I think that’s the Long Range) that is a bit slower than the performance. I think the single motor has a smaller battery so while more efficient has a shorter actual range.
Bjorn Nyland publishes all of his test results spreadsheets (just google “Bjorn Nyland Spreadsheet” which include these cars so I’ll look it up later.
Certainly for the i4 the single vs twin motor has a fairly significant efficiency difference . The larger wheels on the twin motor will be part of that of course.
The single motor cars are plenty quick though - the i4 40 is publishes at 5.7 secs 0-100kph but it is apparently actually a bit quicker - more like 5 secs. Is also feels quicker than the equivalent 0-60 ICE car, as in an ICE that’s recorded when everything is wound up - engine in the powerband, turbos on boost etc - all a bit noisy and frantic plus to switch from “normal” driving to accessing this level of acceleration means changing down a couple of gears waiting for the turbos to spool up etc. in an EV it’s instant - always there with no pause.
I had a 530D as a courtesy car a few weeks back - that’s quite a as 5.4 secs 0-60 and knowing BMW it’s probably actually a little quicker. If felt genuinely slow compared to the i4! Sure when the 530 was wound up it pulled hard, but that performance just wasn’t available without all the changing down palaver, so in “real world” driving it’s not a quick car at all in comparison.
There is a small penalty, compare a Model 3 LR to a Model 3 Performance. Same size battery, 10% less range.
That’s predominantly caused by the stupid big and heavy 20in wheels on the Performance model.
But in day to day use, I’ve never found it an issue, other than requiring extreme care when parking!