EVs in a jam.

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soupdragon1

3,966 posts

96 months

Friday 28th February 2020
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Mr E said:
A vaguely related note, and not surprising given that physics is a thing.

Changed commute. I now go down a motorway for a junction.
When you only have the equivalent of about 3 litres of petrol in the tank (24Kwh) the difference between 50 and 70mph is really significant. Motorway speeds drop my efficiency from 4 miles/Kw to about 3.3 miles/Kw.

When you see a hen 1 leaf drafting a truck on the inside lane, now you know why.
The 3 litres comparison is hardly relevant, when you consider a car with throw about 80+% of that energy away when converting it to kinetic energy.
I don't know the number off the top of my head, but when converting electric energy to the equivalent fuel energy, electric cars deliver in the region of 150MPG due to not throwing most of the energy away like an ICE car does.

ZesPak

24,421 posts

195 months

Friday 28th February 2020
quotequote all
soupdragon1 said:
The 3 litres comparison is hardly relevant, when you consider a car with throw about 80+% of that energy away when converting it to kinetic energy.
I don't know the number off the top of my head, but when converting electric energy to the equivalent fuel energy, electric cars deliver in the region of 150MPG due to not throwing most of the energy away like an ICE car does.
yes
ICE engines use 2/3 of the fuel to get hot, the other third is to move the car. That is in ideal circumstances, real numbers will probably be lower.

Mr E

21,583 posts

258 months

Friday 28th February 2020
quotequote all
soupdragon1 said:
The 3 litres comparison is hardly relevant, when you consider a car with throw about 80+% of that energy away when converting it to kinetic energy.
I don't know the number off the top of my head, but when converting electric energy to the equivalent fuel energy, electric cars deliver in the region of 150MPG due to not throwing most of the energy away like an ICE car does.
Having dabbled in physics from time to time, I’m aware of this. I thought it might bring home the difference in energy density and the effect of aero to EV’s.

I guess my point was; if you’re concerned about running a heater for a couple of hours sitting still, you can probably extend your range by driving a bit slower should you need to. You know, just like a normal car.

Edited by Mr E on Friday 28th February 16:28