Electric company cars

[Whoppa Choppa]

On 27/02/2022 at 10:01, openspaceman said:

It needs to be a bit more refined than that but I hope someone critiques my figures; a petrol engine at maximum torque is more efficient then a naturally aspirated diesel, except most diesels are now boosted by a turbo and the common rail injection means they burn their fuel much higher up the stroke so they become more efficient. Then cars seldom work in their most efficient range (40% with a big old diesel) . Again IC cars don't recoup energy as they slow down (even though this is actually a small amount in normal driving air and rolling resistance use most energy) and tend to use fuel when stationary.

 

For our purposes we only need to consider the energy input verses mileage.

 

My little diesel fiesta when I got it at 4 years old managed 80mpg 17.6 miles per litre on a long run. As each litre of DERV contains about 10kWh of heat energy that means I did 1.76 miles per kWh of heat. An average car is probably worse than twice that.

 

Your lower figure of 30% heat to electrical power to a consumer is about right for a steam turbine power plant but only coal, nuclear and biomass power plants use them now as far as I know. Most of our electricity comes from combined cycle gas turbines which operate at 60+% heat to electricity, a lot comes from renewables which have no heat input.

 

So even at your lowest generation to consumer figure of 30% the EV doing 4 miles per kWh is doing 1.2mile per kWh of heat and if it is charged off peak it will be having input from a combination of wind and nuclear so even less heat energy and of course much lower cost if you can get an off peak tariff.

 

And that's even before we start looking at the comparative pollution levels from centralised generation versus a diesel engined vehicle.

This bit here:

 

"petrol engine at maximum torque is more efficient then a naturally aspirated diesel, except most diesels are now boosted by a turbo and the common rail injection means they burn their fuel much higher up the stroke so they become more efficient"

 

Is completely wrong. No petrol or constant volume cylinder cycle is more efficient than a diesel constant pressure cycle. You are right that often maximum torque is where maximum efficiency is, but not in a engine with restricted inlet. Modern diesels have swirl flaps - stupid. Modern petrols have no throttle, so the wide open flow is more similar. "Burn their fuel much higher up the stroke" would actually be LESS efficient in any cylinder. It is a factor of fuel lag that means that SI flame is over and done with long before the piston is much down the cylinder i.e. constant volume. The slow burn of oil means the combustion is still propagating with the piston halfway down the bore or more hence constant pressure. Never the twain shall meet. To try and make a CI engine complete it's burn asap after tdc would really make into something other than a diesel. 

 

Turbocharging and fuel injection type has absolutely nothing to do with cylinder burn time. High injection pressures are about improving mixing* (which reduces lag) combined with DI vs IDI.

Edited August 23, 2023 by Whoppa Choppa

[Squaredy]

If anyone is interested, after having an electric car for three and a half years, I have now handed it back and bought a new one.  

 

New car also electric but different brand and a little bigger.

 

 Overall I am very happy with the electric experience.  So far I have found EVs super cheap to run, but of course pricey to buy. 
 

My old car has been faultless until last week when it decided to discharge its little battery just because the car had its doors open for two hours and I guess the interior lights were on.  It felt ridiculous to open the bonnet and put a traditional battery charger on the little 12v battery when I know there is a massive 400v battery in the floor which could power my sawmill for a whole day.

 

 Anyway, after an hour or two of charging all was ok and the car is nice and clean and sparkly to hand back to the leasing company.

 

 If anyone wants to know, I will update on here in the future how the new car is.  It is an outright purchase this time not a lease, which has tax drawbacks, but still owned by my company not by me.

[Steve Bullman]

Which model did you get? Bet the acceleration is an improvement on what you had before!

 

I had one on pre-order back in 2020, then covid hit so I cancelled due to the uncertainty 

[Squaredy]

1 hour ago, Steve Bullman said:

Which model did you get? Bet the acceleration is an improvement on what you had before!

 

I had one on pre-order back in 2020, then covid hit so I cancelled due to the uncertainty 

I got the extended range RWD model.  This gives the best possible range on one charge - up to 400 miles in summer.  Not super fast - 0-60 is about 7 seconds, roughly the same as the Kia.  To be honest Steve electric cars are so quick off the mark it is all a bit daft.  Two of the test drive cars I tried out had 0-60 times of around three seconds.  What is the point?  I live in Wales remember, the land of 20mph roads (and of song).

 

Which one were you after?

[Steve Bullman]

4 minutes ago, Squaredy said:

I got the extended range RWD model.  This gives the best possible range on one charge - up to 400 miles in summer.  Not super fast - 0-60 is about 7 seconds, roughly the same as the Kia.  To be honest Steve electric cars are so quick off the mark it is all a bit daft.  Two of the test drive cars I tried out had 0-60 times of around three seconds.  What is the point?  I live in Wales remember, the land of 20mph roads (and of song).

 

Which one were you after?

I think it was the standard rwd we put a deposit on, can’t remember now 

[Squaredy]

1 hour ago, Steve Bullman said:

I think it was the standard rwd we put a deposit on, can’t remember now 

Will you think about it again or has that that ship sailed?

[Steve Bullman]

Hmmm not sure. We took the missus's car off the road during covid and we've been a 1 car family ever since. Getting to the point now with the shop that a second car would be useful again though. I'd probably say at this point it wouldn't be electric.

[Rich Rule]

I’ve had an Audi Etron 55 for over two years now.  Purely a family car.

 

Not been a bother at all.  Charges quicker than other with the Eessee box we have installed.  Get just under 4 hundred KM on full charge.  Only usually charge to 80% for daily use.  
 

The infrastructure we have here in Norway is geared for electric, cheaper parking, sometimes free, get to use bus lanes and cheaper tolls.  If just had the 30000km checkup service which was free as part of the deal when I bought it.

 

It is plenty fast and has loads of torque when motorway driving and generally German Audi build quality and finish.

 

Very happy with it and would have another.  

 

[Squaredy]

2 minutes ago, Rich Rule said:

I’ve had an Audi Etron 55 for over two years now.  Purely a family car.

 

Not been a bother at all.  Charges quicker than other with the Eessee box we have installed.  Get just under 4 hundred KM on full charge.  Only usually charge to 80% for daily use.  
 

The infrastructure we have here in Norway is geared for electric, cheaper parking, sometimes free, get to use bus lanes and cheaper tolls.  If just had the 30000km checkup service which was free as part of the deal when I bought it.

 

It is plenty fast and has loads of torque when motorway driving and generally German Audi build quality and finish.

 

Very happy with it and would have another.  

 

Do you still get the nonsense like we have in the UK that many of the public charging points need an app to use?

[Rich Rule]

5 minutes ago, Squaredy said:

Do you still get the nonsense like we have in the UK that many of the public charging points need an app to use?

Yes, you still get the best rates on the road using the apps.  But once it is setup you just use your phone and it doesn’t take long.  I also have an Audi charge card which is a monthly invoice.