How many have changed brake pads? At what mileage? Record?

[JeremyW]

As the cells degrade their internal resistance rises. Internal resistance is one of the factors that determines the maximum acceptable charge rate. Consider regen to be a form of fast-charging. As the internal resistance increases and the overall capacity decreases, the maximum charge rate will decrease. The computer adjusts the regen parameters to match this reality.

To flesh this out: What the car is doing is limiting regen as the cell voltage rises, which is caused by increases in internal resistance. Essentially, there is a high cell voltage limit that the battery management system wants to stay under, and it will demand regen and fast charging limitations in order to do so.

I am two bars down in my car, and I rarely see all of my regen circles lit up, even down to 4 bars of SOC (120 Gids or so) and pack temperatures approaching 30 C. My car tapers fast charging current at as little as 35% SOC. When the car was new the taper began around 50%. The effects of increased internal resistance on the leaf are very much real.

 

[derkraut]

I'm confused as to why you would lose regen with a degraded battery? I get that you'd charge to 100% and thus you wouldn't get full regen until you get down to something like 91%, but why would it effect it at other percentages? A degraded battery should simply mean that you don't have the same maximum capacity, why would it matter under normal driving?

Don't ask me, I'm not an engineer. I just know it does.

Max regen hits 30kW, so unless someone has a video to prove that a degraded battery can't regen back at this level under 80% charge, I would say the information is incorrect.

I'm @ 10 bars, 24K miles; and I haven't noticed any reduction in re-generation.. with light pedal pressure, I get 30KW regen. Edited to add: that 30KW only works when my GIDS are down below 75 or so.

 

[knightmb]

No video "proof" will be forthcoming. If you chose not to believe, I'm more than willing to leave you with your own delusions.

None needed, I drive a Leaf with a degraded battery and hitting 30kW regen is easy enough with a outside temperature above 60F and a speed of say 50MPH with a charge state of 80% of less. No delusions here, experience trumps logic.

 

[pchilds]

Last time I fast charged, I only got 22kW into the battery at 27% SOC, just above LBW.

 

[DaveEV]

No delusions here, experience trumps logic.

I think what you really mean to say "my experience trumps yours" since you believe that your experience must be the same as everyone else's.

Anyway, there's quite a few variables here that affect the amount of regen available at any point in time:

1. Year of car ('11-12 LEAFs appear to have less regen than '13+ LEAFs in general)
2. Whether or not P3227 update has been applied (P3227 significantly reduces the Hx value in the BMS which subsequently significantly reduces available regen)
3. Hx value - highly correlated with remaining capacity available all else being equal. Lower values = less available regen.
4. Temperature of battery - colder batteries = less regen available
5. Speed of vehicle - lower speeds = less regen available, down to about 10-15 mph or so

The biggest variable here between otherwise similar vehicles is the P3227 update. Please read the What happened to my Regen? thread for way more information than you'd like to know.

My 10-bar, 50.6 Ah 58.1 Hx 2011 LEAF and 75-80F battery temps, SOC needs to be below 50% along with speeds of 20-30 mph for regen to touch 30 kW briefly. A new LEAF under similar conditions will far exceed 30 kW in regen. I use a lot more friction brakes than I used to.

 

[knightmb]

I've read plenty here and really at this point it has gotten way off topic. When the original question came up, the user asking the question already understood how the Leaf works in regards to how much regen is sent back into the batteries based on state of charge, battery temperature, etc. The only response to the question was "it just does" with no further elaboration to the answer. That was still incorrect when the only information was "you loose most of your regen due to battery degradation" and "it just does" is the reason.

The truth is much more complex than that as has been elated in this topic and I still stand by my challenge to the answers given by others. I'll be glad to concede that my response was only a disagreement and didn't offer much more than a challenge to prove otherwise, but I see often that misinformation in this forum does not go unchallenged. I am glad to challenge blanket statements that everyone driving a leaf has already lost most of their regen due to battery degradation and certainly that the reason behind this is "just because".

The experience trumps logic phrase comes from something that seems logical but testing proves otherwise. Kind of like the urban legend that leaving your tailgate down on a pickup truck gives you better gas mileage than leaving it up. Logically, it would seem that leaving the tailgate down would create less air drag and thus better gas mileage, but the reality is leaving the tailgate up gives you better gas mileage because it creates an air bubble in the back to deflect air over the truck instead of pushing the air directly down on the bed, thus breaking the air bubble and increasing drag that results in less gas mileage for the truck.

 

[JeremyW]

Max regen hits 30kW, so unless someone has a video to prove that a degraded battery can't regen back at this level under 80% charge, I would say the information is incorrect.

I'll happily provide a youtube video tomorrow!

 

[DNAinaGoodWay]

Well to answer the original question I am at 36 months, 28,887 miles, and just had my annual inspection & battery check performed. My front brakes were at 6mm, and the rear brakes were at 7mm which is just about halfway worn. The service advisor cautioned me that I should keep an eye on them, but I think it will be fine. I have a lot of stop and go traffic with the Hampton Roads Bridge Tunnel everyday and such, and base traffic going in to Naval Station Norfolk. So my brakes will not be representative of the majority, but most likely accelerated wear.

Thanks for that. Your scenario probably comes closest to the worst case for brake wear in a LEAF.

Under this type of use, wouldn't the weight of the LEAF tend to wear the pads more than a similar sized ICE?

 

[garsh]

Under this type of use, wouldn't the weight of the LEAF tend to wear the pads more than a similar sized ICE?

The brakes on the Leaf are sized more like a larger car than a smaller one, given the two-piston calipers up front. They're about the same size as the brakes on my Honda minivan. So I would still expect them to wear better than in any ICE.

 

[garsh]

I made a point of monitoring my regen tonight. Three bubbles worth is about 15kW, and this is the most I can achieve right now under optimal circumstances.

There's an energy usage screen in the Nav unit that provides a "dial" with kW scale that you can use to better estimate the actual regen power.

I am two bars down in my car, and I rarely see all of my regen circles lit up

One of the software updates (P3227?) appears to be the main cause of this. I was often able to obtain full regen before the update, and it was much more strictly curtailed afterwards, even before I lost any bars.

 

[mwalsh]

There's an energy usage screen in the Nav unit that provides a "dial" with kW scale that you can use to better estimate the actual regen power.

That's what I used to get my numbers.

 

[tractioninc]

Thanks guys - learn something new each time I check in on the forums.

 

[TomT]

With a three bar degraded battery and P3227, the best I could get under any circumstances was about 15Kw of regen... Reality trumps everything else.

None needed, I drive a Leaf with a degraded battery and hitting 30kW regen is easy enough with a outside temperature above 60F and a speed of say 50MPH with a charge state of 80% of less. No delusions here, experience trumps logic.

 

[TomT]

+10

and even more loss if you had P3227 done!

...until you loose most of your regen due to battery degradation, and find yourself on the brakes WAY more than when you first got your car.

 

[JimSouCal]

After an atypical near freezing weather overnight fall season mountain stay at about 6,500 elevation, and charged to 80% on my 11bar MY2011 LEAF, I experienced almost zero regen braking (and no charging) on the descent to 1000 ft.

It's an easy step in logic that anyone commuting regularly in such conditions will wear through pads more rapidly than typical LEAF drivers, and with the larger weight of battery pack, perhaps more...

Member Abasile might eventually comment, or those who commute down to Denver from higher elevations...

My empirical observation is the regen is greatly reduced as compared to the first software implementation as sold.

 

[tkdbrusco]

Is it safe to say that with a degraded battery there is no purpose for B mode?

 

[mwalsh]

Is it safe to say that with a degraded battery there is no purpose for B mode?

It's too early to say yet whether a degraded battery should be a near-term concern to a 2015 owner. I wouldn't worry about it for now. And remember, we don't have B mode in the earlier cars, just ECO.

 

[dhanson865]

With a three bar degraded battery and P3227, the best I could get under any circumstances was about 15Kw of regen... Reality trumps everything else.

None needed, I drive a Leaf with a degraded battery and hitting 30kW regen is easy enough with a outside temperature above 60F and a speed of say 50MPH with a charge state of 80% of less. No delusions here, experience trumps logic.

The Gen2 (NHW20) Prius tops out at about 21kw peak regen. The Leaf tops out at 30kW

That's sad that a degraded Leaf might have less regen than a Prius considering the vast capacity difference in the HV packs.

I don't have one but I'm planning to get a 2011/2012 with a few bars missing now that they are sub $9000 used and I'd be disappointed if the regen is less on the Leaf than what I was used to on the Prius.

 

[dhanson865]

Another important thing to remember in this argument is that Nissan has programmed the Leaf to respond similarly to brake pressure no matter what the SOC of the car battery. In other words, at 90% SOC, light pressure on the brake might yield 1/5th the total possible regen but X amount of deceleration. Nissan had to make sure this same X amount of deceleration would be seen by applying the same amount of force on the brake even with a 20% SOC when the battery is looking to gobble up all the electrons it can take via full 30kW regen. I have little doubt that what you may feel is a "weak" regen is in some large measure Nissan's way of making sure that the car behaves identically no matter what the SOC. After all, it wouldn't do for a car with empty batteries to screetch to a halt via regen as soon as you ease off the gas yet have no regen effect at all when the car is at 100% SOC. That would feel like swapping back and forth from an exhaust-brake-equipped ICE with massive engine-braking forces to an electric car with no regen capabilities.

I sure hope that if degredation limits the regen from the prior peak of 30KW down to 15KW that it is all on the gas pedal regen and the lost regen is taken away from the brake pedal side of the controls.

mwalsh and others can you clarify how much of the 30KW max regen is allocated to which pedal and if that allocation ratio changes with degredation?

 

[Nubo]

... the max regen the car can produce is 30kW, but how much is fed back into the battery depends on factors such as state of charge, battery temperature, software version for model year and just plain physics. A degraded battery that can put out 80kW of power to drive the car can certainly accept 30kW back in for a recharge. ...

Probably, but there may be a difference between what's possible, and what's prudent. And then there may be a difference between what's prudent and what a Nissan engineer thinks is prudent for cells from a particular model year. And then there may be a difference between what an Nissan engineer thinks is prudent and what a Nissan executive thinks is prudent. And finally there may be another difference when that executive is fretting about how to manage a debacle involving premature degradation of LEAF batteries in the field....