EV Owners Thread

[icowden]

I find motorway driving to be the least economical. Constant high speed with no ability to recover anything via the brakes. You can almost see the numbers dropping before your eyes. Pottering around town is best for me.

Absolutely, but some cars are definitely better than others both due to battery capacity and aerodynamics. I have no issue getting to the Birmingham gigahub in the ID4 from Surrey travelling at motorway speeds with a decent amount left in the tank, but for the Leaf it's touch and go, 60mph driving ideally. On paper the ID4 has about 250miles and the leaf 150. The distance to the hub is about 90 miles.

 

[BrumJim]

Sounds like a plan. It looks like there are a few chargers in the port area at Harwich.

Will also need to charge between Hook of Holland and Assen. Since we need food, will probably stop at a Jumbo or Lidl on the way, and charge there.

Would go via UAE, but a bit of a detour. And UNO-X too, but they only serve petrol.

 

[icowden]

Would go via UAE, but a bit of a detour. And UNO-X too, but they only serve petrol.

Yep - don't try putting petrol in. The car will be wet, smelly and flammable (although not as much as in the movies)

 

[Drago]

Those of you with Ohme chargers will have noticed the woeful app has been updated and is now much better to use.

 

[roubaixtuesday]

Drag coefficient is the most important as is low speed, wind resistance not being linear but exponential.

Wind resistance is proportional to the square of speed, so power to the cube.

Not exponential.

 

[albion]

Exponential was certainly correct. It gets used for 'rapid'.

 

[icowden]

Not exponential.

I'm going to have to agree with @albion and also with you. If air resistance were not exponential we would not get terminal velocity. That said, at slower speeds it is linear, so it depends on the object as to whether the wind is linear or exponential.

 

[roubaixtuesday]

Exponential was certainly correct. It gets used for 'rapid'.

Rapid and exponential are not synonymous

 

[roubaixtuesday]

If air resistance were not exponential we would not get terminal velocity.

Is, I'm afraid, incorrect.

The formula:

From https://en.m.wikipedia.org/wiki/Drag_(physics)

Note the velocity squared term, no exponential term.

This applies at high Reynolds numbers, which will be the case for a car due to dimensions and speed.

I think you're meaning "non- linear" rather than "exponential".

 

[albion]

You're an exponential drag.

 

[icowden]

I think you're meaning "non- linear" rather than "exponential".

Nope. GCSE Physics:-
https://www.tutorchase.com/answers/ib/physics/how-does-air-resistance-impact-a-falling-object

The effect of air resistance is also dependent on the speed of the falling object. At low speeds, the air resistance is proportional to the speed. However, as the speed increases, the air resistance increases exponentially. This is why objects falling from a great height, such as skydivers, reach a terminal velocity. Terminal velocity is the constant maximum speed that a freely falling object eventually reaches when the resistance of the medium through which it is falling prevents further acceleration.

ALso:-

When taking into account other factors, this relationship becomes FD=1/2 CρAv(squared). where C is the drag coefficient, A is the area of the object facing the fluid, and ρ is the density of the fluid. (Recall that density is mass per unit volume.) This equation can also be written in a more generalized fashion as FD = bv2, where b is a constant equivalent to 0.5CρA. We have set the exponent n for these equations as 2 because, when an object is moving at high velocity through air, the magnitude of the drag force is proportional to the square of the speed. As we shall see in a few pages on fluid dynamics, for small particles moving at low speeds in a fluid, the exponent n is equal to 1.

 

[roubaixtuesday]

Nope. GCSE Physics:

Yes, that's exactly what my post says; drag is dependent on Reynolds number, but for a car, Reynolds number is large, so drag coefficient close to constant

 

[roubaixtuesday]

You're an exponential drag.

Sure. But I am correct.

 

[figbat]

This appears to be an argument of semantics. In its pure mathematical form, "exponential" has a specific meaning that isn't satisfied by equations for drag (the exponent is constant). In its informal form, "exponential" is used to mean non-linear, usually in an increasing way.

With freefall there comes an equilibrium between drag force and acceleration due to gravity; terminal velocity is as much a function of g as it is drag. With a vehicle the acceleration is down to applied power, so with unlimited power the speed will continue to increase, with drag continuing to increasing with the square of speed. The equilibrium is reach when the applied force matches the drag from aerodynamics and friction.

 

[BrumJim]

Sounds like a plan. It looks like there are a few chargers in the port area at Harwich.

Well, that was epic.