Brakes Fail upon Powering On

[TimLee]

... I'm just saying I charge my battery with a CTEK in addition to the Nissan provided systems. ...

I do to.

With the five times typical drain on the 12V caused by the Bluetooth adapter, which I find more trouble to unplug even though it is on an OBDII extension cable due to time to re-pair with phone, I hook up CTEK every time I charge the LEAF.

It doesn't do much effective top off while LEAF is charging, but when LEAF charging finishes I disconnect the J1772, and restart the CTEK analysis and topping off and only disconnect it from the 12V before I drive off.

[miscrms]

Thought these might be of interest, some notes out of the 2012 service manuals (June 2014 Rev) related to 12V battery charging.

EVC-48: Automatic 12V Battery Charge Control
DESCRIPTION
The automatic 12V battery charge control is a control to reduce the frequency of battery discharge by automatically charging the 12V battery in case the 12V battery voltage is low when the key switch is turned to ON or the vehicle is left unattended for a long time.
When VCM judges a need for automatic charge, VCM controls the DC/DC converter and the system main relay and charges the 12V battery using the Li-ion battery power.
For 12V battery charge control during READY condition, refer to EVC-48, "POWER VOLTAGE VARIABLE CONTROL SYSTEM : System Description".

PG-9: 12V Battery
Note: VCM charges the 12V battery for 5 minutes when the vehicle power is not turned on for a set period of time (120 h).

EVC-48: Power Voltage Variable Control System
DESCRIPTION
The power voltage variable control system reduces the electric power consumption from the Li-ion battery by
varying the DC/DC converter output in a range from 13 V to 15 V according to the use status of electric equipment and the 12V battery status.
CONTROL DESCRIPTION
The battery current sensor (with battery temperature sensor) measures the battery charge/discharge current and the battery ambient temperature.
VCM judges the battery status and the use status of electric equipment based on those signals, determines a target output voltage, and transmits a target DC/DC output power signal to the DC/DC converter.
The DC/DC converter adjusts the output voltage to the target power generation voltage based on the received target DC/DC output power signal.
In addition, when there is no power voltage signal or when some error is occurs in the variable voltage control system, the DC/DC converter outputs 14 V.

[RegGuheert]

Thought these might be of interest, some notes out of the 2012 service manuals (June 2014 Rev) related to 12V battery charging.
...
EVC-48: Power Voltage Variable Control System
DESCRIPTION
...
VCM judges the battery status and the use status of electric equipment based on those signals, determines a target output voltage, and transmits a target DC/DC output power signal to the DC/DC converter.
...

The problem with the 12V battery charging system in he LEAF lies in this part. Unfortunately, when the car is OFF, the VCM cannot know how much energy is being used from the 12V battery. As a result, it makes an estimate when you start the vehicle how much charge to replace. Unfortunately, it is overly optimistic in many operating scenarios, resulting in only a fraction of the energy which was lost being replaced. The unfortunate result of that is a 12V battery which spends most of its life at 60% SOC, which leads to sulfation (hardening of the lead sulfate) and early death.

The good news is that the battery uses very little water in the LEAF's charging regime. If you charge it to full occasionally with a good quality trickle charger, it should last a very long time.

[Levenkay]

The problem with the 12V battery charging system in he LEAF lies in this part. Unfortunately, when the car is OFF, the VCM cannot know how much energy is being used from the 12V battery. As a result, it makes an estimate when you start the vehicle how much charge to replace. Unfortunately, it is overly optimistic in many operating scenarios, resulting in only a fraction of the energy which was lost being replaced. The unfortunate result of that is a 12V battery which spends most of its life at 60% SOC, which leads to sulfation (hardening of the lead sulfate) and early death.

Thanks for the explanation; that pretty much clears up the mysteries of the LEAF's poor 12V reliability. Obviously, the VCM's 12V battery monitor functions should be powered from the 12V battery always, and not just when the car is ON. Low power design is a hot engineering topic these days; it should be completely feasible to do. And just TRY to claim it would be more expensive per car than replacing 12V batteries every year or two...

[RegGuheert]

Obviously, the VCM's 12V battery monitor functions should be powered from the 12V battery always, and not just when the car is ON. Low power design is a hot engineering topic these days; it should be completely feasible to do. And just TRY to claim it would be more expensive per car than replacing 12V batteries every year or two...

Even if it did/does that, it would have a very difficult time monitoring the load current when the car is off. The reason is that the monitoring system needs to be able measure hundreds of amps, but it would need to be able to resolve about 5 mA in order to know what is going on when the car is off. If the system used a 1 mohm shunt, that would mean an instrumentation system capable of resolving 5 uV with about 20 bits of resolution. (Alternatively, multiple shunts could be used for different loads on the battery, which may be what is done.)

Another solution is simply to be pessimistic about how much energy was drained while the car was off and replace more than what it thinks is needed. That would cause a bit more water to be consumed, but it would still be an improvement over the current approach as well as older-style charging systems which hold the voltage at 14.5V when the vehicles is on.

[DesertSprings]

Exact same thing happened to me today. Started my 2013 Nissan Leaf and put it in reverse and almost immediately the car started moving back. Since my drive way has a considerable slope, the car moved fast. Brakes felt soft and no resistance. Had to slam the brakes pretty hard to the floor to get the car to stop. Turned the car off and started it back on after few mins. Still the same issue. Moved the car to Drive and it did the same thing. Slammed the brakes again hard to stop the car. Left the car there for a while and started it after an hour and everything seems normal now. Took the car to the dealer (Corona Nissan) and explained the problem.

What did the dealer end up doing? I'm experiencing the same thing and have an appointment to bring my Leaf in to Corona Nissan tomorrow.

For those keeping track:
2015 S Model
<10,000 miles

I had the T/M System Malfunction, where not only did the breaks not work, but basically nothing worked. Stereo console got stuck in a reboot loop. I charged the 12v using a battery tender I use on my motorcycle (1.5 amp), and have now had the same problem but instead of T/M System Malfunction I got the red BRAKE light and yellow ! in a circle.

I also have had an issue that when I park the car and turn it off, a high pitch note is played, but no lights show up on the dash. Opening closing door doesn't do anything, walking away doesn't do anything. Turning the car on/off (foot on brake) causes the chime to stop.

[miscrms]

Have any Leaf owners tried switching to a good quality deep cycle AGM type battery? I went to an Optima Yellowtop on my 2005 Prius, which is also notorious for undercharging 12V batteries, and have had no issues for 5 yrs. Even in Phoenix, which also tends to also be tough on 12V battery life.

It does seem surprising to me that the Leaf uses a flooded type battery, as well as a conservative charging routine. The only advantage of a 12V flooded I can think of is its tolerance to more aggressive charging. I guess the explanation is in the "reduces the electric power consumption from the Li-ion battery" statement, seems like they went a bit too far in the efficiency direction.

The Leaf does also use a 12V backup capacitor bank as someone else mentioned the Prius does. So its a little surprising that it could still get into this sagging voltage failure mode if that is indeed the cause. Unless I guess the 12V voltage is just not sufficient to charge the cap bank sufficiently? But that voltage should come up quickly as soon as the DC/DC converter engages when going ready? There are DTCs in the brake system and VCM for low 12V voltage, but they don't seem to trip until 10V or so.

Still it doesn't seem like a total brake failure should be possible even if the electronic control system fails completely. According to the manuals (and my own experimentation) there is still manual hydraulic braking force available in the event of a complete system failure. In my case this was simulated by disconnecting all control and power connections to both the ABS and IBU/master cylinder. Without the boost pump I will say the braking is very heavy, and the pedal position quite low from what I recall. So if the brake boost motor cuts out it may well feel like you've lost the brakes, but a firm pressure on the pedal should still stop the car.

Additionally its perhaps worth noting that the parking brake can (according to the manuals) be used while the vehicle is in motion to apply mechanical cable driven force to the rear brakes as long as the handle is pulled up. Of course this motor does depends on 12V power, but not sure how sensitive it is to voltage.

Rob

[Ninjarider1978]

Exact same thing happened to me today. Started my 2013 Nissan Leaf and put it in reverse and almost immediately the car started moving back. Since my drive way has a considerable slope, the car moved fast. Brakes felt soft and no resistance. Had to slam the brakes pretty hard to the floor to get the car to stop. Turned the car off and started it back on after few mins. Still the same issue. Moved the car to Drive and it did the same thing. Slammed the brakes again hard to stop the car. Left the car there for a while and started it after an hour and everything seems normal now. Took the car to the dealer (Corona Nissan) and explained the problem.

What did the dealer end up doing? I'm experiencing the same thing and have an appointment to bring my Leaf in to Corona Nissan tomorrow.

For those keeping track:
2015 S Model
<10,000 miles

I had the T/M System Malfunction, where not only did the breaks not work, but basically nothing worked. Stereo console got stuck in a reboot loop. I charged the 12v using a battery tender I use on my motorcycle (1.5 amp), and have now had the same problem but instead of T/M System Malfunction I got the red BRAKE light and yellow ! in a circle.

I also have had an issue that when I park the car and turn it off, a high pitch note is played, but no lights show up on the dash. Opening closing door doesn't do anything, walking away doesn't do anything. Turning the car on/off (foot on brake) causes the chime to stop.

An update on the vehicle is they still have it. They called the day it went in and said they updated the firmware again. I asked what the difference was between fridays firnware upgrade and this new one. He said that they are instructed to put this new fireware on if the other one doesnt work. He mentioned the vehicle was working fine again but then asked if it was ok to keep the vehicle until the next day for observation and so they could consult with nissan canada and nissan japan to ensure the problem is fixed. I ablige and patiently wait for a call the next day. At 4pm they called and said they would like to keep it longer and they would give me a rental vehicle if i needed it. I asked how long they expected to need it, he said hopefully just a day but it could be longer. To be safe i accepted the rental because these things alway take longer than expected. My wife and i believe that because our vehicle experienced the problem after the fix was applied that it makes it good to study. So they asked to keep it longer so they can ensure the update will work and put it through its paces. They can then hopefully use that info to apply to other vehicles. I think us raising the issue with transport canada has helped push it this direction.

That being said, i really want it back because the replacement ICE sucks bad.

Will keep you updated if they get back to me today. I asked for constant communications but the tech i was in contact with is off today so i expect to hear from them tomorrow.

Mike

[RegGuheert]

Have any Leaf owners tried switching to a good quality deep cycle AGM type battery? I went to an Optima Yellowtop on my 2005 Prius, which is also notorious for undercharging 12V batteries, and have had no issues for 5 yrs. Even in Phoenix, which also tends to also be tough on 12V battery life.

Several LEAF owners have done this. One issue is that the 13.1V float voltage used by the LEAF can actually be LOWER than the standing voltage for these batteries when fully charged. In other words, the LEAF charger may actually DISCHARGE the battery if fully charged rather than simply failing to charge it. At least one owner has installed a Li-ion 12V replacement battery.

It does seem surprising to me that the Leaf uses a flooded type battery, as well as a conservative charging routine. The only advantage of a 12V flooded I can think of is its tolerance to more aggressive charging.

They are also cheaper.

I guess the explanation is in the "reduces the electric power consumption from the Li-ion battery" statement, seems like they went a bit too far in the efficiency direction.

Agreed.

The Leaf does also use a 12V backup capacitor bank as someone else mentioned the Prius does.

That's true, but only for MY2011/2012. In MY2013 and later LEAFs, backup braking power is provided by a hydraulic acumulator.

So its a little surprising that it could still get into this sagging voltage failure mode if that is indeed the cause. Unless I guess the 12V voltage is just not sufficient to charge the cap bank sufficiently? But that voltage should come up quickly as soon as the DC/DC converter engages when going ready?

It seems that the ultracapacitor in the MY2011/2012s must be charged above a certain level before the brakes will work, even if the voltage in the car is fine. I know this because my dealership could not deliver the car to me after reprogramming the brakes due to the technician not knowing how to recharge the ultracapacitor. But it did eventually charge up on its own.

Still it doesn't seem like a total brake failure should be possible even if the electronic control system fails completely. According to the manuals (and my own experimentation) there is still manual hydraulic braking force available in the event of a complete system failure. In my case this was simulated by disconnecting all control and power connections to both the ABS and IBU/master cylinder. Without the boost pump I will say the braking is very heavy, and the pedal position quite low from what I recall. So if the brake boost motor cuts out it may well feel like you've lost the brakes, but a firm pressure on the pedal should still stop the car.

The technician who had the problem with my car said the pedal went straight to the floor..

Additionally its perhaps worth noting that the parking brake can (according to the manuals) be used while the vehicle is in motion to apply mechanical cable driven force to the rear brakes as long as the handle is pulled up. Of course this motor does depends on 12V power, but not sure how sensitive it is to voltage.

The electrical parking brake system was replaced with a mechanical one starting with MY2013.

[miscrms]

Thanks for the replies, interesting changes!