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Discussion Starter #1
Suppose you are going down a long gradient at constant speed, say 30 mph. From an energy efficiency point of view, does it make any difference which level of regen you select? I realise that each level will require a different “throttle” position to maintain a constant 30 mph.
 

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Only the amount of regen in kW matters, you can achieve it in several ways even with the preset regen set to level 0 by using brake pedal or cruise control.
 

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Discussion Starter #4
Only the amount of regen in kW matters, you can achieve it in several ways even with the preset regen set to level 0 by using brake pedal or cruise control.
So why is there a choice of regen levels, if they all amount to the same thing?
 

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You’re confusing me. If regen, why the accelerator?

I use setting zero, then use the flaps to go to level 1,2 or 3 depending upon the level of retardation I want when going downhill or braking.
 

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So why is there a choice of regen levels, if they all amount to the same thing?
The regen levels are for your convenience, if you like to have a slight deceleration when the power pedal isn't pressed then you choose regen level 0 or 1. If you like to drive more to the way of "one pedal driving" where the car starts to decelerate more aggressively as soon as you lift the power pedal then you can choose level 2 or 3.
 

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Level 3 will recover more energy than level 2 (which will recover more than level 1) BUT only if you’re not using the accelerator AND it will only recover it for a shorter time as you are decelerating more.
 

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Discussion Starter #9
So you could drive exclusively in level 1, if you wanted, using the accelerator and brake pedals as required. And you wouldn’t actually be using the brake pads any more than in any other level, so the same efficiency. Is that right? So it still seems a bit strange to me that there are a range of retard levels to choose from. Maybe this will make more sense to me when I’ve picked up my “new” Ioniq in a few days’ time.
 

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So you could drive exclusively in level 1, if you wanted, using the accelerator and brake pedals as required. And you wouldn’t actually be using the brake pads any more than in any other level, so the same efficiency. Is that right? So it still seems a bit strange to me that there are a range of retard levels to choose from. Maybe this will make more sense to me when I’ve picked up my “new” Ioniq in a few days’ time.
You have grasped the idea now. You will also grasp the reason for different regen levels also when you get to drive the car. It is fully up to your preference what regen level (levels) you use. Is use only regen level 0 and rarely 1, 2 or 3 when coming down a steep hill and not using a cruise control.
 

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Top line, same efficiency but not really.
Regen is not 100% efficient so it’s best to be in regen 0 and let the car coast as much as possible. That is the most efficient driving.

regen 1,2 or 3 really is a personal style of driving.

‘braking’ using the pedal uses regen before the main brakes so theflappy paddles/brakes do the same thing for regen but the flappy pedals will not brake hard enough to apply the physical brakes (the discs on the rotors).
 

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Discussion Starter #12
Top line, same efficiency but not really.
Regen is not 100% efficient so it’s best to be in regen 0 and let the car coast as much as possible. That is the most efficient driving.

regen 1,2 or 3 really is a personal style of driving.

‘braking’ using the pedal uses regen before the main brakes so theflappy paddles/brakes do the same thing for regen but the flappy pedals will not brake hard enough to apply the physical brakes (the discs on the rotors).
So if level 0 is the most efficient, why would you use anything else?
 

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You don’t have to but I like using the paddles to hold speed going down a hill (As per your original post) and for gentle braking.
You could use the foot brake though to the same effect.
Level 1,2 and 3 do offer a different driving style as level 0 is like driving a car in neutral when you lift and some people don’t like that feeling. I guess Level 1 offers the most similar feeling to an ICE car with normal engine braking.
 

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I think your confusion is that we were answering your initial question literally. You asked about modulating the accelerator pedal, not the brake.
 

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Discussion Starter #15
I think your confusion is that we were answering your initial question literally. You asked about modulating the accelerator pedal, not the brake.
I wanted my question to be taken literally, thanks! I don’t think I’m confused, I am merely trying to establish whether the wheel brakes have to make a bigger contribution to retardation at level 0 than at level 3. The majority opinion on this thread seems to be that the control system is always clever enough to use electric retard to the max and wheel brakes to the minimum, regardless of retard paddle setting. And so there is no difference in efficiency.

In the example I suggested, it would seem that in level 3 it might be necessary to press the accelerator pedal to maintain a certain speed down a shallow hill, whereas in level 0 it might require brake pedal pressure to maintain the same speed. But the contribution of the wheel brakes is the same - probably zero.

This is in contrast to an ICE car, where the wheel brakes would be used more heavily when descending in high gear than in low gear.
 

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richi.uk
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Okay, didn't mean to offend, sorry. I misunderstood your reply.

All modern EVs work this way, but the details can differ. For example, the Outlander PHEV can't achieve maximum regen unless in B5.
 

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Mode 0 for motorways, I use mode 1 for narrow twisting uneven roads.
The Ioniq wiĺ only revert to disc brakes on bumpy roads especially going down hills, but this happens principally in mode 0, and rarely in mode1,2 or 3, so on uneven roads and down hill on country roads I go back to mode 1, not needed on main roads.
 

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... All modern EVs work this way, but the details can differ...
They certainly can! The MG ZS can't do regen when you have cruise control selected, so descending a steep hill in CC mode will operate the discs and waste a lot of energy! I guess they skimped when raiding the parts bin for Cruise Control tech.
 

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Discussion Starter #19
You don’t have to but I like using the paddles to hold speed going down a hill (As per your original post) and for gentle braking.
You could use the foot brake though to the same effect.
Level 1,2 and 3 do offer a different driving style as level 0 is like driving a car in neutral when you lift and some people don’t like that feeling. I guess Level 1 offers the most similar feeling to an ICE car with normal engine braking.
Although.....looking at page 5-19 of the owner’s manual of my newly-acquired 2017 Ioniq, it warns: “When descending down a long or steep hill, use the paddle shifter (left side lever) to increase regenerative braking control in order to control your speed without using the brake pedal excessively. Applying the brakes continuously will cause the brakes to overheat and could result in a temporary loss of braking performance.”
So doesn’t this imply that the brake system is partially or fully independent of the regen system?
 

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richi.uk
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The way it works is that the first inch or so of pedal travel is regen only. Push it further and the car effectively blends regen and braking action. But it's two entirely separate things in one pedal.

It has to be like that for safety: The brake pedal needs to be able to stop the car even if all the electronics fail. So it can't be brake-by-wire.
 
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