[Richard Wood]

Other things being equal ( and that’s the important bit), no. I’ve done deliberate test routes in the past using different settings (level 0 v level 3 etc., ECO, NORMAL, SPORT) and got close results but you need really long runs on the same roads in similar conditions to eliminate or at least minimise all the variables. We recently had just such an opportunity in the e-Niro. 221 miles round trip, me driving out (NORMAL mode, level 0 + AUTO), wife return (ditto but she prefers level 1). Mix of roads, 40-60mph, 5 overtakes (me 2, wife 3), plus 30 miles duals/motorway at 70-ish, air-con working. Set out with 100% and got back with 97 miles on the GOM (4.9 miles/kWh). Repeated the journey yesterday in similar weather but entirely in SPORT mode, same regen. 220 miles and 103 miles still to go on return home (5 miles/kWh --only 3 overtakes this time?). If there is a secret, it’s simple: minimise energy input required to achieve desired progress -- a steady speed around 50mph is the ideal compromise. There’s no point in pratting about doing without creature comforts or stinting yourself on the available power in ECO mode (let alone ECO+).

 

[DragonQ]

How you drive determines efficiency and the modes are just helpers really. The fact that sport mode has a steeper power curve than normal mode makes no difference if you're consciously accelerating at a fixed rate anyway. Also, partly because there are no gears, slow vs fast acceleration doesn't make much difference either.

Regeneration will make a difference if you are doing a lot of stop-starting that you cannot predict. If you always let off the accelerator when coming up to a roundabout or traffic light such that you glide to a near stop anyway, regen won't help. If you're cruising on the motorway for hours, regen won't affect your range noticeably either. However, if you have to stop more suddenly (e.g. car in front decides late that they want to make a right turn), doing more braking with regen instead of traditional brakes will waste less energy. Same if you're driving through town and there are just junctions and roundabouts every 100m: it's impossible to drive through these conditions without using brakes without infuriating those behind you.

Basically coasting > regen > braking. So when you cannot safely coast to a stop, regen > braking.

 

[Todor]

IMO, the regen level (incl one pedal driving) are user interface, so I don't expect there to be any improvement of efficiency.

Drive mode is a little more difficult to judge, as I don't know the actual settings that are changed. The electric motor can't be changed, but the pedal response curve can and indirectly it can impact your driving efficiency. And again, I'm not saying the car's efficiency, but your driving.

 

[Richard Wood]

How you drive determines efficiency and the modes are just helpers really. The fact that sport mode has a steeper power curve than normal mode makes no difference if you're consciously accelerating at a fixed rate anyway. Also, partly because there are no gears, slow vs fast acceleration doesn't make much difference either.

Regeneration will make a difference if you are doing a lot of stop-starting that you cannot predict. If you always let off the accelerator when coming up to a roundabout or traffic light such that you glide to a near stop anyway, regen won't help. If you're cruising on the motorway for hours, regen won't affect your range noticeably either. However, if you have to stop more suddenly (e.g. car in front decides late that they want to make a right turn), doing more braking with regen instead of traditional brakes will waste less energy. Same if you're driving through town and there are just junctions and roundabouts every 100m: it's impossible to drive through these conditions without using brakes without infuriating those behind you.

Basically coasting > regen > braking. So when you cannot safely coast to a stop, regen > braking.

Yep, that's about the size of it. Also, unless you have to stop really sharply, the brake pedal will be using regen to slow, up to as much as pulling the left paddle can do (about 0.24g according to the regen curves I've seen).

 

[Richard Wood]

IMO, the regen level (incl one pedal driving) are user interface, so I don't expect there to be any improvement of efficiency.

Drive mode is a little more difficult to judge, as I don't know the actual settings that are changed. The electric motor can't be changed, but the pedal response curve can and indirectly it can impact your driving efficiency. And again, I'm not saying the car's efficiency, but your driving.

Agreed, as regards regen level, it's a case of whatever floats your boat. Even in level 3 you can spend just as much time hovering around 0 power. The drive modes have progressively steeper torque curves that also top out above each other, but again it's all under the control of your right foot. I suspect the fact that the car won't default to SPORT mode is Kia's attempt to stop you caning the battery too often.

 

[metastable]

If you drive each mode at the limits of acceleration performance in a stop start environment I'd expect to see some efficiency difference between modes.

 

[Richard Wood]

If you drive each mode at the limits of acceleration performance in a stop start environment I'd expect to see some efficiency difference between modes.

As I said at the beginning, other things being equal .... Obviously, there is a temptation in SPORT mode to get more of a wriggle on, but if you drive the same as usual, the energy required is the same.

 

[ShEV]

Also, partly because there are no gears, slow vs fast acceleration doesn't make much difference either.

I agree with everything else, but not this. the battery losses (and other resistive losses) are proportional to current squared.

Let's say you need 10kW for normal driving (a current of about 28A) and you choose to accelerate as here:

Case (a) - Accelerate quickly, let's say in 5s, with 60kW power

Current ~ 60,000/356 = 168A

Losses are proportional to 168^2 x 5s + 28^2 x 5s ~ 145040

Case (b) - Accelerate slowly, let's say 10s at 30kW

Current ~ 30,000/356 = 84A

Losses proportional to 84^2 x 10s = 70560

So the losses in the rapid acceleration case are 2.05 times greater. So you would arrive a bit quicker, reducing aerodynamic losses and rolling friction, but only 5s quicker (if you only did it once ) , so roughly speaking the losses are twice as big.

 

[Richard Wood]

Maybe so, but he did say 'not much difference' and in practice that appears to be the case. Internal pouch cell resistance is very low and there are 3 in parallel, so even with the whopping currents of a spirited overtake, the loss is minimal in the grand scheme of things - not least because of the very short duration.

 

[metastable]

Let's say you need 10kW for normal driving (a current of about 28A) and you choose to accelerate as here:

Case (a) - Accelerate quickly, let's say in 5s, with 60kW power

Current ~ 60,000/356 = 168A

Losses are proportional to 168^2 x 5s + 28^2 x 5s ~ 145040

Case (b) - Accelerate slowly, let's say 10s at 30kW

Current ~ 30,000/356 = 84A

Losses proportional to 84^2 x 10s = 70560

So the losses in the rapid acceleration case are 2.05 times greater. So you would arrive a bit quicker, reducing aerodynamic losses and rolling friction, but only 5s quicker (if you only did it once ) , so roughly speaking the losses are twice as big.

It's a bit more complicated.

Resistive losses in watts (W) in the battery are equal to the battery current (I), squared, multiplied by the battery's internal resistance (R)

I^2R = W

Resistive losses in watts (W) in the motor are equal to the motor current (I), squared, multiplied by the motor's internal resistance (R)

I^2R = W

What makes it more complicated are the majority of resistive losses occur in the motor, not the battery (blue line, bottom middle chart), and the motor current is nearly always significantly higher than the battery current.

Motor Current (I) = (Battery Voltage (V) * Duty Cycle (D)) - Back EMF Voltage (B)) / Motor Winding Resistance (R)

Battery Current (I Bat)= (Motor Current (I) * (Battery Voltage (V) * Duty Cycle (D))) / Battery Voltage (V)

^When the battery current is constant (red line top left chart 25mph and above), the resistive losses in the motor (blue line bottom middle chart) and motor current (blue line, top left chart) decrease with increasing velocity.

 

[ShEV]

Are those charts from the MatLab Vehicle Dynamics tool? I used it once to compare the actual performance of my old Leaf to theoretical!

Whilst it's undoutedly more complex than I said, I would stand by the fact that it will be better to accelerate more slowly; for one, the charts show that ohmic losses in the motor depend on the range over which you are accelerating, so if we were talking about main road driving I guess the answer would be subtlety different to urban driving, but also whilst accelerating slowly means that you spend less time in the inefficient motor region, you end up spending more time at higher speed with higher aerodynamic losses and they appear to be higher than the motor ohmic losses in the middle top chart, but I'll happily let you interpret that for me as they are a bit difficult to get your head round!

 

[Bodgerx]

It's often been said that rolling/coasting and avoiding regen-ing to stop/slow down is more efficient.

But in the real world it isn't always the case, as sometimes you can't roll/coast due to traffic or a hill being so steep you'd be out of control/breaking limits.

For example, I have a trip to my parents whereby there is a long drag of about a 1.5 miles of gradual descent. If you coast in a 38kwh Ioniq with that you'd be over the limit. I adjust the regen to level 1 and it is just enough to bring it below 60mph. Following that descent is a further 0.5 miles of steep descent. Moving the regen to level 3 for that claims almost 2kwh back in the battery over 2 miles.

So regen where you need to, but aim to coast.

 

[KiwiME]

I think the answer to the OP's question is "no" in ideal conditions, noting that the context is assumed to be from a theoretical perspective. Both settings just present the driver with different calibrations of the user interface. However, the resulting change in sensitivity of both may result in unintentional ergonomic-based losses, as implied by the posts above. For example in Level 3 regen just lifting your foot momentarily off the accelerator pedal for a rest incurs significant regen and your economy suffers regen-related losses rather than preferably using that momentum to 'carry on', the same reason why the ECO drive modes have a softer pedal calibration. Level 0 (coasting) avoids that and ensures regen is only used when intended, that is by pressing the brake pedal.
With the "rubber band" effect in Level 3 it's easy to be fooled into thinking that accelerating and regening are both the same energy-wise, but regen losses can add up quickly if that is frequently used.

 

[Richard Wood]

All true. And, again, I did say 'other things being equal'. Loved your 'rubber band effect', by the way.

 

[Richard Wood]

Are those charts from the MatLab Vehicle Dynamics tool? I used it once to compare the actual performance of my old Leaf to theoretical!

Whilst it's undoutedly more complex than I said, I would stand by the fact that it will be better to accelerate more slowly; for one, the charts show that ohmic losses in the motor depend on the range over which you are accelerating, so if we were talking about main road driving I guess the answer would be subtlety different to urban driving, but also whilst accelerating slowly means that you spend less time in the inefficient motor region, you end up spending more time at higher speed with higher aerodynamic losses and they appear to be higher than the motor ohmic losses in the middle top chart, but I'll happily let you interpret that for me as they are a bit difficult to get your head round!

I'll stick to practical observations, and leave the theorising to you!

 

[DangerousDoug]

One point not so far mentioned is brake pad wear vs regen level. I drive on max. regen all the time, to get the "one pedal driving" effect, including holding the left paddle when decellerating to stop, all so as to minimise brake use. I'm not sure how much it helps range during normal decel while driving, but if it avoids actual braking, this will of course save some energy (otherwise you'll be using battery power to heat up the brakes) and reduce brake pad (and disk) wear. This, surely, is a good thing, even if in the grand scheme of things it makes little difference to overall running costs.

 

[DragonQ]

Doesn't the brake pedal only do regen if you use it lightly anyway?

 

[DangerousDoug]

The brake pedal itself is not causing any regen - that's happening because you've come off the accellerator so you're on the over-run (the defining condition for regen). The brake pedal (now being called the "friction brakes" in EV land, to differentiate from regen braking) just apply the brake pads, causing energy loss due to friction (basically throwing away your kinetic engergy, instead of putting it back in the battery through regen). That's why EV drivers tend to develop a smooth, anticipating driving style, whereby you look a long way ahead and seek to start slowing down long before actual braking would be necessary. This maximises range while minimising brake pad wear .

 

[John Page]

Doesn't the brake pedal only do regen if you use it lightly anyway?

The brake pedal will only use friction brakes after it has called up the maximum amount of regenerative braking available at the current speed.

 

[niggle]

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