Nissan Leaf brake failure reports a concern

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7972 posts

Uber Geek

#2133798 25-Nov-2018 15:52

DJK01:And the brake cylinder still needs regular tip ups of brake fluid.

If it needs topping up, then there is a leak. Cars should have enough capacity in the reservoir to account for pad wear. The fluid should be changed every two years though, as it is hygroscopic.

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zenourn

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#2133799 25-Nov-2018 15:56

tripper1000:

Also, regen brakes gets disabled if the ABS or traction control kicks in as the computer can not shift the regen braking force to individual wheels but can modulate the individual wheel brakes hydraulically. So I guess if a rear wheel was to start slipping it will cut regen braking on the front wheels and increase (presumably) the hydraulic brakes, which will have a delay, change the pedal feel and momentarily alter the cars (nose-diving) attitude.

I've driven in a car in the failure-mode and it sounds like the the ABS system is getting completely confused. Even at a complete stop and in park, pushing down on the pedal the ABS system goes crazy. When in motion, you get no braking for half of the pedal distance as the input rod crosses the cooperative regenerative brake control gap, but then start to get braking (and lots of noises from the ABS) as you contact the master cyclinder. Once you get used to it I think you could actually drive reasonably OK in failure mode.

DJK01

29 posts

Geek

#2133800 25-Nov-2018 15:57

It seems not that common, or there would have been a recall or lots of reported failures, but nevertheless it has happened. Would a reason for those brake failures have been not enough charge in the 12V battery? Or some other reason? And crucially, how to prevent it from happening? Yes, regenerative braking is a good idea and will save on brake pad wear, but you still need good brake, especially in a case of emergency stopping.

tripper1000

1543 posts

Uber Geek

#2133802 25-Nov-2018 16:00

In the linked cases it may also be related to tire selection - as a generally rule most Leafs run on Eco tires, which are specifically designed for lower friction. I have noticed in the Leaf when getting cut off or cornering too fast, is that it simply doesn't corner or brake as hard with those blimmin Eco tires. My ICE (with RE003 tyres) will be tearing your face off with G force, but not so much in the Leaf. I drive my ICE way harder than the Leaf (especially when I was younger and more reckless), but I can honestly say I've come closer to uncontrollably going wide on high speed corners in the Leaf than my ICE.

I switched my Mrs Kia from Eco tires to RE003's and she is no speed demon, but still noticed the improvement in wet weather traction.

DJK01

29 posts

Geek

#2133806 25-Nov-2018 16:17

Tires are always important and definitely not worth cost cutting. For our ICE (old Mercedes) I'm liking the new Continental Contact 6. Yesterday we visited EV World South here in Christchurch, and that question came up. The reply was that EV tires cost much the same as is performance. Maybe. The BMW i3, which I rather like, has skinnier tires for low rolling resistance and I hear it corners OK. Lower center of gravity will help, too.

Scott3

3340 posts

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Lifetime subscriber

#2133841 25-Nov-2018 16:32

The leaf has quite bad 12v battery management (in short it has a powerful DC-DC converter rather than an alternator to keep the 12V battery topped up, but it is set to charge to a lower voltage than is typical for efficiency reasons. Enough voltage to maintain charge, but not enough to charge the battery properly). Also has issues with only charging the 12V at the start of a traction battery charging session, and not kicking back in if the 12V battery voltage falls (such as if you leave the car plugged in for a week - car plugged in means computers etc fired up to manage charging process so higher 12V consumption).

It is rumored that a lot of weird leaf issues (including this one) are to do with weak 12V battery output. Some people charge their leaf 12V batteries with an external smart charger every fortnight of so to avoid this, and extend the life of their 12V battery.

zenourn

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#2133842 25-Nov-2018 16:37

Scott3:

The leaf has quite bad 12v battery management (in short it has a powerful DC-DC converter rather than an alternator to keep the 12V battery topped up, but it is set to charge to a lower voltage than is typical for efficiency reasons. Enough voltage to maintain charge, but not enough to charge the battery properly). Also has issues with only charging the 12V at the start of a traction battery charging session, and not kicking back in if the 12V battery voltage falls (such as if you leave the car plugged in for a week - car plugged in means computers etc fired up to manage charging process so higher 12V consumption).

It is rumored that a lot of weird leaf issues (including this one) are to do with weak 12V battery output. Some people charge their leaf 12V batteries with an external smart charger every fortnight of so to avoid this, and extend the life of their 12V battery.

It is the Gen 1.1 Leafs which have the worst 12V battery management and they don't have any evidence of this particular issue.

tripper1000

1543 posts

Uber Geek

#2133865 25-Nov-2018 17:48

My Leaf spontaneously flattens the 12v battery twice a month, so while I agree that the 12v battery system leaves a lot to be desired, what I have seen is that the Leaf keeps the 12v buss at a decent voltage for running the 12v systems (just not an OK voltage for long enough to float or absorption charge the 12v battery). If you have Leaf-Spy running on your phone you get to see what is going on in the 12v system.

When the 12v battery is down around 8-10 volts the computers in the car go banana's with dozens of error codes and bad behavior which could certainly mess with the brakes. Usually you can't even start the car in this state, and on the odd occasion when you can, it immediately boosts the 12v system to 14.4v which means everything works properly again.

afe66

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#2133866 25-Nov-2018 17:54

Just to balance reporting bias.

I've have a 2015 leaf for 3 years still on it's original 12v battery and had no issues.

frednz

1452 posts

Uber Geek

#2133954 25-Nov-2018 20:51

zenourn:

Are now aware of 5 of these failures in NZ - see https://flipthefleet.org/2018/leaf-brakes-failures/ for a lot more details!

From the above report:

"Globally, there could be tens of thousands of vehicles that are currently running either the factory-installed ‘Series-A’ firmware or the updated ‘Series-B’ firmware, and are therefore prone to this failure. In New Zealand, specifically, we estimate there are around 2,400 potentially vulnerable vehicles, with a vast majority still running the factory-installed ‘Series-A’ firmware version."

Wow, 2,400 potentially vulnerable vehicles in New Zealand!

So will a firmware update fix the problem? The report says:

"...we have been told that EVs Enhanced are indeed capable of installing later firmware versions of the brake control unit onto certain Nissan Leafs."

"… we do not know for sure that an upgrade of the brake control unit’s firmware will completely remove the chance of a failure occurring, reduces the chances of a failure occurring or perhaps even increases the chances of a failure occurring."

So should affected Leaf owners get a firmware update? Does Nissan NZ offer this update?

Also from the report:

"I have one of these vehicles - is it safe for me to drive it?

We’d love to answer this question, but we simply can’t"! We put this question to Nissan, but have not received their reply. Ultimately, we believe it is the role of the national regulator to make this judgement, as the definition of ‘safe to drive’ varies from country to country. In New Zealand, our regulators are New Zealand Transport Agency (“NZTA”) and New Zealand Ministry of Transport (“MOT”), and while we made both entities aware of our preliminary findings on October 22, 2018, via our memo, neither has provided us with a formal evaluation and a statement whether they consider the vehicles safe to drive by November 23, 2018."

"Flip the Fleet" are taking this matter very seriously as they conclude that:

"We urge Nissan and the New Zealand government to urgently evaluate, manage and publicly disclose the risks posed by this brake fault, and to provide an immediate remedy."

zenourn

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#2134021 25-Nov-2018 21:38

frednz:

Wow, 2,400 potentially vulnerable vehicles in New Zealand!

So will a firmware update fix the problem? The report says:

"...we have been told that EVs Enhanced are indeed capable of installing later firmware versions of the brake control unit onto certain Nissan Leafs."

"… we do not know for sure that an upgrade of the brake control unit’s firmware will completely remove the chance of a failure occurring, reduces the chances of a failure occurring or perhaps even increases the chances of a failure occurring."

So should affected Leaf owners get a firmware update? Does Nissan NZ offer this update?

We asked the question whether the series-C brake firmware fixes this issue but never received a reply. So we can't say whether a firmware update fixes this. However, lets just say I don't have any safety concerns with my wife and kids using our Leaf which is running the series-C brake firmware.

Installing the firmware update is not a trivial process and requires expensive equipment and takes nearly an hour. Nissan NZ has no responsibility for these vehicles (they didn't import or sell them) and don't offer the firmware update.

At this stage I think the most important message for people with the potentially vulnerable vehicles is that if it does happen to you, you need to press down *very hard* and completely ignore the strange noises (if present) and feel of the pedal. Based on the data we have now, can expect 4 to 23 (95% uncertainty interval) of these failures in NZ over the next year.

DJK01

29 posts

Geek

#2134696 26-Nov-2018 16:27

Well, that report just reinforces my original concerns that have been reported extensively online overseas. It puts us off getting one. Safety is paramount. Also, Nissan should have the decency to at least respond. There are other EVs around, with more to come.

Batman

Mad Scientist
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#2134704 26-Nov-2018 16:35

brake failure is not new, Toyota Prius (IIRC) had braking issues didn't they? Resulting in a few deaths in the US (or so claimed). anything that involves complex computer circuitry has a high potential to fail (watch formula 1) than those that rely on simpler systems.

frednz

1452 posts

Uber Geek

#2134898 26-Nov-2018 19:56

zenourn:

We asked the question whether the series-C brake firmware fixes this issue but never received a reply. So we can't say whether a firmware update fixes this. However, lets just say I don't have any safety concerns with my wife and kids using our Leaf which is running the series-C brake firmware.

Installing the firmware update is not a trivial process and requires expensive equipment and takes nearly an hour. Nissan NZ has no responsibility for these vehicles (they didn't import or sell them) and don't offer the firmware update.

At this stage I think the most important message for people with the potentially vulnerable vehicles is that if it does happen to you, you need to press down *very hard* and completely ignore the strange noises (if present) and feel of the pedal. Based on the data we have now, can expect 4 to 23 (95% uncertainty interval) of these failures in NZ over the next year.

I would have thought that we now have enough evidence of these brake failures to warrant a recall of all Leafs that are likely to be affected by this. After all, people could be killed by such a failure, that's why "Flip the Fleet" is treating this issue as highly important.

We had a similar experience with Nissan not dealing early enough with the 30kWh Leaf issue of apparent "fast battery degradation", but thankfully Leaf owners can now get an official Nissan NZ patch for this problem.

The problem with third party "unofficial" firmware patches is that they have not been authorised for use by Nissan in NZ and they may not be entirely reliable. So, if insurance companies get a sniff of this, they mightn't be too happy insuring Leafs until this matter is resolved.

You also have to think of warrants of fitness, if it's known there's a potential brake failure issue, couldn't there be a tightening up of issuing warrants to affected vehicles that have not been repaired with an official NZ Nissan firmware patch?

MichaelNZ

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Integrity Tech Solutions

#2134940 26-Nov-2018 22:51

Batman: Are they brake by wire? I never want to buy anything that is electric controlled if possible. Electric steering, electric throttle, electric braking ... why!

Electric steering is not drive by wire.

It simply replaces a hydraulic system with a powerful electric motor.

Lots of 2xxx model cars have it. Including mine. You may well have driven electric power steer without realising it as it feels the same.

Electric power assisted steering (EPS/EPAS) or motor-driven power steering (MDPS)

"A mechanical linkage between the steering wheel and the steering gear is retained in EPAS. In the event of component failure or power failure that causes a failure to provide assistance, the mechanical linkage serves as a back-up. If EPAS fails, the driver encounters a situation where heavy effort is required to steer. This heavy effort is similar to that of an inoperative hydraulic steering assist system.

[....]

Electric systems have an advantage in fuel efficiency because there is no belt-driven hydraulic pump constantly running, whether assistance is required or not, and this is a major reason for their introduction. Another major advantage is the elimination of a belt-driven engine accessory, and several high-pressure hydraulic hoses between the hydraulic pump, mounted on the engine, and the steering gear, mounted on the chassis. This greatly simplifies manufacturing and maintenance. By incorporating electronic stability control electric power steering systems can instantly vary torque assist levels to aid the driver in corrective maneuvers."

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