Can't "feather" brake pedal to modulate regeneration anymore

I have a 2014 Leaf SL. Up until a few months ago, it was possible to "feather" the brake pedal and control how much regenerative braking power was applied. Now, it seems that after lifting off the accelerator at say 50-60km/h (30-35mph) I get some regeneration (say 10KW or 1 bubble). As I start to apply brake, at first nothing changes and then at some point, the regeneration jumps to the maximum (around 30KW or 4 bubbles.)

Before, I could gently increase the amount of brake pressure and the regeneration would smoothly increase from 10 to 30KW. I have had the vehicle into the dealer and they have no explanation other than all the diagnostics check out fine.

I did find a vague reference on another site indicating that the computer may decide that the friction brakes haven't been worn enough and change the braking behaviour. So, I tried doing some hard braking to try and "reset" things, but so far that hasn't helped.

Any ideas would be greatly appreciated.

It might be that new software update they put out as their fix to a recall related to the brakes. I've seen a few posts here where that has really changed the braking/regenerative characteristics.

If that update has been applied to your car, which it is supposed to if it is ever in the shop, then it probably is to blame. And I don't think you are allowed to retro back to the old programming. :roll:

Where are you? Can you update your location info via your user name in the upper right > User Control Panel > Profile tab? That way, we don't need to ask in future posts/threads or do sleuthing to deduce it.

What's the outside air temperature and what % SoC are you at when you have this problem? How many regen double circles do you have to the left? Are all of them double circles or are some not? You will have little regen at high SoC and have less regen at low temps.

What if you shift into B mode instead?

Thanks for the replies. I'm in western Canada. The temperature has been between 0-7 degrees C over the last few months. Th problem happens at all states of charge (well of course all but very near 100%). As indicated, I did have it into the shop in the past few weeks, but that was after the problem started happening. Before that, it hadn't been in for about 10 months. Unless they sent an update over the air, nothing I can think of prompted the change.

Should have mentioned the 'B' mode. The behaviour is basically the same except when you lift off the accelerator, the regen jumps to about 20KW initially, but once again, beginning to apply brake pressure initially does nothing, then it jumps to 30KW.

There are 4 total regen circles available. I don't know what a "double circle" is. They are just round green indicators that illuminate as I described originally.

If the issue was first noticed after the Leaf was in the shop this last time, then it is probably the programming of the update.

lightning said:

I did find a vague reference on another site indicating that the computer may decide that the friction brakes haven't been worn enough and change the braking behaviour. ...

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That sounds like a level of sophistication I wouldn't expect from Nissan software designers. :lol:

But seriously, wouldn't a cardinal safety rule be to have CONSISTENT braking behavior? Ah well, maybe this is why I'm not a car designer. :roll:

@Graffi, thanks, but as indicated the issue started occurring BEFORE the recent visit to the dealer.

This seems to be a common problem. My brakes modulate well at faster speed then tend to grab at low speed. The software is definitely not too refined, though implementing two different braking biases because of B mode and regular mode complicates things.

I wish Nissan would have done a better job of this function. I hope they spent the time and effort minimizing the risk of unintentional loss of braking - that's what I worry about!

Seems no one is familiar with the problem I am seeing so far. Ie., no brake pedal reaction (other than the brake lights turn on) initially until you have pushed the brake far enough and then regen jumps to the max (and I assume friction brakes also start being applied.)

Is this a safety issue? Anyone familiar with exactly how the sensor in the brake pedal actually signals the computer?

Further information: I did a little bit of experimentation today and found the following:
1) Lift off accelerator - 1 bubble of regen
2) Start applying brake, no change
3) Continue to apply brake and the regen jumps to 4 bubbles
4) Reduce the brake pressure and now it is possible to "feather" the brake pedal to control the regen anywhere from 1 to 4 bubbles by applying more or less brake pressure.
5) But, as soon as you release the brake completely, and reapply, the phenomenon happens again.

I wonder if the brake switch is somehow bad or stuck or something. Seems like the car isn't properly detecting the start of braking.

Yeah, something is definitely wrong. Haven't heard anyone describe that behavior before. Sounds like some sort of sensor that detects brake pedal travel (either directly or indirectly).

I've noticed an issue with mine (2011 model) that may be related - sometimes when I come gently to a stop at the traffic lights (after using the regen as much as possible, of course!) the friction brakes will 'grab' quite abruptly. If I am moving slowly in stop-start traffic, the car will 'lurch and grab' as I release and apply the bake.

At first I thought the pedal sensor was going wrong, but then I noticed that it only does it when I've been driving really economically and not applying the brakes hard. I found that if I pump the brakes firmly a couple of times while stopped, things get much smoother. I conclude that the system has an automatic calibration built in so that it knows the point where the friction brake makes contact, and if you don't use the brakes enough, the calibration seems to drift (at least on mine). It's not as simple as it seems, because the computer has to modulate the regen just the right amount in the available pedal travel (which changes with brake wear and temperature). Even more complex, the car is designed to 'creep' a bit when in drive, with the brakes off, but I am pretty sure they cut the power when the brakes are applied to save energy. This has to occur at the correct pedal position, especially when on a hill, for example!

electricjay said:

I've noticed an issue with mine (2011 model) that may be related - sometimes when I come gently to a stop at the traffic lights (after using the regen as much as possible, of course!) the friction brakes will 'grab' quite abruptly. If I am moving slowly in stop-start traffic, the car will 'lurch and grab' as I release and apply the bake.

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Your issue is covered in quite a bit of detail here: Grabby Brakes?.

Different issue than what the OP is reporting, though.

I’ve been searching for other people to have had this issue and keep finding the grabby brakes at low speed problem, but it’s not the same as this.

I have the exact same problem as you. It’s like the brake pedal does nothing for the first couple of centimetres of travel and then suddenly activates full regen rather than allowing a varied amount.

Did you find a fix?

Nope, just got used to it. I switch into B mode now if I want more than the 1 green of just taking the foot off the gas.

Another thing I have noticed is if you have your foot on the brake and are getting regeneration, if you go over even a small bump, regen cuts out. I think disabling traction control will stop that from happening.

I do this about once a month or so.

Grabby at high or low speeds? There's a (temporary?) fix if it happens at low, which is: Turn off traction control, inch forward, hold and press down the brakes FULLY for about 30 seconds. That's it. Mine used to be super grabby on/off style at low speeds, but now they're normal.

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from this thread

https://www.mynissanleaf.com/viewtopic.php?f=30&t=19108&p=412477&hilit=brake#p412477