Electric car anyone?
1 lurker |
72 watchers
Jul 2021
10:52pm, 18 Jul 2021
39,231 posts
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HappyG(rrr)
Made it back with 50 miles to spare. It doesn't like motorway compared to urban or sub urban tootling about, does it? Comfortable drive though.  G
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Jul 2021
11:34pm, 18 Jul 2021
15,108 posts
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larkim
I don't know anything about ICE power curves but I'd presume there is no difference in the power to overcome drag etc so the battery drain of a EV at higher speeds should reflect the petrol consumption at similar speeds, but because the in car readouts aren't as precise so you don't notice. Or is the efficiency of an ICE higher at bigger power outputs? |
Jul 2021
7:35am, 19 Jul 2021
12,523 posts
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mrs shanksi
50 miles is loads HappyG, I can remember our dial reading 0 miles as we drove home from Aberdeen one time! Was great to see you x
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Jul 2021
9:15am, 19 Jul 2021
39,234 posts
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HappyG(rrr)
larks, I think they can be different. Different power generation systems will have different outputs at which they will be more or less efficient. If you put the motor/engine on a laboratory bench, I think you would measure an efficiency curve that is different between the two. I don't know why, but it seems that electric motors are better at low speed, high torque, lots of braking (regeneration), not at rolling along at a high, constant rpm. Or conversely, the ICEs are bad at stop start (relatively), and are more efficient at constant, steady rpm. Intuitively makes sense to me, but I can't give you a scientific explanation. So I'll use a rule of thumb of 250 max for motorway type driving, so about 80% of the estimated range. But will trust the 100% of range estimate when I'm pootling around locally. Was nice to drive. I like all the speed and lane aids when on motorways and dual carriageways! G
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Jul 2021
9:40am, 19 Jul 2021
15,114 posts
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larkim
HG - thanks for that; prompted me to google. Seems that an IC engine has a sweet spot in the "middle", so low and high speed are both inefficient, but the middle output is most efficient. EVs don't lose efficiency at high speed, the motor is pretty consistent throughout the range of operation in terms of power output per energy input. Interesting stuff!! en.wikipedia.org |
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Jul 2021
11:02am, 19 Jul 2021
39,237 posts
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HappyG(rrr)
Is that middle 56mph by any chance? Or is that the drag+engine sweet spot. Will go read the link now, after asking the question that the link answers! G
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Jul 2021
11:04am, 19 Jul 2021
15,118 posts
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larkim
I think 56 is just 90km/h so is an industry standard for measurement of a "fast cruise". Each car and engine will have it's own sweet spot due to gearing / drag / mass / power curve etc.
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Jul 2021
11:06am, 19 Jul 2021
39,238 posts
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HappyG(rrr)
Larks, that article is about power band and while that relates to efficiency (so energy out for energy in) not quite sure that's the same as fuel/battery use. Not sure now, thinking about it. But I think it bears out the idea that ICE and electric have a different efficiency profile and generally that ICE has a problem at urban end. Whether that excuses EV manufacturers being overly optimistic for the motorway end, I can't say! G
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Jul 2021
11:09am, 19 Jul 2021
39,239 posts
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HappyG(rrr)
I think how things like "efficiency" are expressed may change and standardise over time for EV. For ICE, the most common way of expressing MPG (or litres/100km if you are being metric!) is at 4 points: Urban Optimum (56mph) Motorway Combined I think something similar should come out for EVs. They are all based on absolutely optimum conditions (and using very light right foot! - and according to my wife, removing the seats and lots of other dodges!) but at least it would show that real world performance will vary with the proportion of different types of driving that you might do? |
Jul 2021
11:32am, 19 Jul 2021
146 posts
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theOtherRichard
Is that gaming of the system not what WLTP is supposed to counteract G? wltpfacts.eu Though given that it's probably an EU standard, presumably the UK may not continue down that path. |
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