My Nissan leaf rolled off around 400ft

[cwerdna]

The backup method for when the fob battery is dead or you washed the fob too many times (mine got stuck in the gasket of the washer for month(s)) is passive (I presume something very much like RFID). You put the fob near the start button and the car is able to read the ID of the fob. Once started you can put key away. Unless directly near the start button the car can not pickup the fob. I actually keep this in the car as a backup. Thus all I need to do if I loose my keys is have a locksmith unlock the door. On could do the same thing by taking the battery out of the fob.

Yes, I know about this mode. I suspect that there's a coil in/near the power button to induce current in the key itself so that it can respond if the fob battery's dead.

On the Gen 3 (2010+) Prius, they removed the slot that was present on then Gen 2 Prius for the dead battery reason and make you also hold up the key to the power button.

So what I am saying is if in park and the active key disappears the car could shutdown but if it was started with passive mode it would just stay running. I bet the car is already aware of this as I bet if you start the car with only the passive mode and then exit the car with it running it likely doesn't honk at you.

As for bolded part, it could disappear for any # of reasons such as interference, signal blocked, key battery dies, key battery removed, etc. It would be a bad idea to just shut the car off if shifted into park if it no longer detects the key, as it could be any of those reasons.

 

[QueenBee]

The backup method for when the fob battery is dead or you washed the fob too many times (mine got stuck in the gasket of the washer for month(s)) is passive (I presume something very much like RFID). You put the fob near the start button and the car is able to read the ID of the fob. Once started you can put key away. Unless directly near the start button the car can not pickup the fob. I actually keep this in the car as a backup. Thus all I need to do if I loose my keys is have a locksmith unlock the door. On could do the same thing by taking the battery out of the fob.

Yes, I know about this mode. I suspect that there's a coil in/near the power button to induce current in the key itself so that it can respond if the fob battery's dead.

On the Gen 3 (2010+) Prius, they removed the slot that was present on then Gen 2 Prius for the dead battery reason and make you also hold up the key to the power button.

So what I am saying is if in park and the active key disappears the car could shutdown but if it was started with passive mode it would just stay running. I bet the car is already aware of this as I bet if you start the car with only the passive mode and then exit the car with it running it likely doesn't honk at you.

As for bolded part, it could disappear for any # of reasons such as interference, signal blocked, key battery dies, key battery removed, etc. It would be a bad idea to just shut the car off if shifted into park if it no longer detects the key, as it could be any of those reasons.

I have no idea how reliable the connection is but I don't think it is a bad thing for the car to go out of ready mode if it's in park... Realistically though the car knows the key is now outside the car when you leave the car so even if that caused it to shut down if it was in park thst would certainly be safer. Obviously some people would prefer to be able to keep their car running and be able to lock the doors so it would have to be a setting thst could be disabled.

 

[cwerdna]

I have no idea how reliable the connection is but I don't think it is a bad thing for the car to go out of ready mode if it's in park... Realistically though the car knows the key is now outside the car when you leave the car so even if that caused it to shut down if it was in park thst would certainly be safer. Obviously some people would prefer to be able to keep their car running and be able to lock the doors so it would have to be a setting thst could be disabled.

I do. It can create confusion and leave the driver stuck if suddenly the car shuts down if the shift to park at a light or because of a extended traffic jam. It could even create a safety issue due to an unnecessary extended traffic backup that results (i.e. cars shouldn't be a standstill w/moving traffic around them longer than necessary).

Again, the key can lose communication for any number of reasons, while still inside the car. Heck, I recall some folks reporting Priuses having trouble locking or unlocking if their smart key is in the same pocket as their phone.

We've had basically the same argument before on Priuschat (http://priuschat.com/threads/prius-gen-iii-does-not-switch-off-when-key-is-removed.91406/" onclick="window.open(this.href);return false. BTW, ignore the crap from tpfun, who fortunately was finally banned after months of trolling there (his trolling was very frustrating to many of the long-timers).

BTW, back to my 1st point, about unexpected power offs leading to potential confusion, take a look at http://www.mynissanleaf.com/viewtopic.php?f=30&t=12066" onclick="window.open(this.href);return false;. I believe it was as case of either a glitch or user error (actually turning the car off instead of putting it in park) followed by more user error of not putting their foot on the brake while pushing power.

Two Leaf veterans also believe they've hit a similar glitch before: http://www.mynissanleaf.com/viewtopic.php?p=279715#p279715" onclick="window.open(this.href);return false; and http://www.mynissanleaf.com/viewtopic.php?p=280464#p280464" onclick="window.open(this.href);return false;.

I really don't think adding such heuristics as you describe is a good idea, given the possible communication loss/signal interruption/interference issues.

 

[QueenBee]

I have no idea how reliable the connection is but I don't think it is a bad thing for the car to go out of ready mode if it's in park... Realistically though the car knows the key is now outside the car when you leave the car so even if that caused it to shut down if it was in park thst would certainly be safer. Obviously some people would prefer to be able to keep their car running and be able to lock the doors so it would have to be a setting thst could be disabled.

I do. It can create confusion and leave the driver stuck if suddenly the car shuts down if the shift to park at a light or because of a extended traffic jam. It could even create a safety issue due to an unnecessary extended traffic backup that results (i.e. cars shouldn't be a standstill w/moving traffic around them longer than necessary).

Again, the key can lose communication for any number of reasons, while still inside the car. Heck, I recall some folks reporting Priuses having trouble locking or unlocking if their smart key is in the same pocket as their phone.

We've had this same argument before on Priuschat (http://priuschat.com/threads/prius-gen-iii-does-not-switch-off-when-key-is-removed.91406/" onclick="window.open(this.href);return false. BTW, ignore the crap from tpfun, who fortunately was finally banned after months of trolling there (his trolling was very frustrating to of of the many long-timers).

Thinking about it more I bet if you were to remove the battery of the FOB with the car on it doesn't honk the horn. I bet it only does so when there is no FOB in the car AND it detects a fob outside the car. So given that it likely works that way I'd like to modify my suggestion to use the logic of only when it detects a fob outside the car with none inside the car as while as being in park.

But in the end KISS, this just makes a complicated car more complicated for what is ultimately the responsibility of the driver.

 

[DaveinOlyWA]

P is not a brake at all. it works just like a normal car in that it engages a notch to hold the car in place.

Agreed, but a normal car doesn't pop out of park and into neutral when it runs out of gas. I can see why Nissan would program the LEAF to do this, but I think it's a safety concern if it does it from park. A car should never, automatically, go from park to neutral. That's a lawsuit and massive safety recall waiting to happen.

And unless there is a major bug the LEAF doesn't go out of park automatically on its own under any condition.

Seems like the most likely explanation is it was left in D and was held in place by the creep until the battery went dead. Then the LEAF switched to neutral and rolled back down the driveway. It may make more sense for the LEAF to instead go into park if the car isn't moving when this occurs though...

right and there is probably some missing info on this story. but normal can be different for different people. I know someone whose LEAF died and they had to be towed. problem is the LEAF was sooooo dead it would not power up at all which meant there was no way to disengage the parking prawl so the car had to be dragged up onto the flat bad at great effort. the guy was lucky enough the tow truck had a winch strong enough to do this but during this event, the prawl did not give way which has to make one think that perhaps the OP's prawl is defective. it is likely a spring loaded solenoid and all springs wear out.

 

[Devin]

I'll never understand why people choose to not use the parking brake. Do you imagine something bad will happen if you set the parking brake "unnecessarily"?

This is really the most important take away here. When I learned to drive, I learned to set the parking brake as a part of the procedure for turning off a car. It doesn't matter if you're on a hill or not. It also doesn't matter if you're in the country where nobody is likely to come steal your car - you should treat a car the same way you should treat a loaded firearm. If you are leaving it unattended it needs to be properly powered down and the key goes with you. As the owner of a car (which is a privilege, not a right) this is just basic safety responsibility. People need to be a little more aware that a car is not just an appliance to get you from A to B, but like any power tool is capable of causing great bodily harm or death if not treated with adequate respect.

 

[RegGuheert]

I'll never understand why people choose to not use the parking brake. Do you imagine something bad will happen if you set the parking brake "unnecessarily"?

This is really the most important take away here. When I learned to drive, I learned to set the parking brake as a part of the procedure for turning off a car. It doesn't matter if you're on a hill or not. It also doesn't matter if you're in the country where nobody is likely to come steal your car - you should treat a car the same way you should treat a loaded firearm. If you are leaving it unattended it needs to be properly powered down and the key goes with you. As the owner of a car (which is a privilege, not a right) this is just basic safety responsibility. People need to be a little more aware that a car is not just an appliance to get you from A to B, but like any power tool is capable of causing great bodily harm or death if not treated with adequate respect.

I know many people around here who do not set the parking brake. Why not? Because in wet, cold, winter weather, you can have a situation where wet brake shoes or pads will freeze to the drum overnight. The result can be an undriveable car.

I have had the brake pads on the LEAF freeze to the discs a couple of times, but I was able to get them to break free. Drum brakes can be much worse.

 

[lion]

Just for the record (and I would be surprised if this is what happened here), my 2013 LEAF got stranded once because the 12V batter died after sitting at the office for 10 hours, yet I knew for sure I turned the car off that morning (dashcam confirmed this). A faulty door sensor prevented the car from turning off completely, which allow the 12V battery to be drained. While I didn't see anything on the dashboard, the mechanic told me that the computer was still running.

I've seen folks rely on the car automatically going to P when turning off the car (personally, I'm so paranoid, I visually check once-twice before shutting down that it is in P), so weird stuff IS possible, but if you verify your car is in P, and ALWAYS set the emergency brake, this would have been prevented anyways.

I'll never understand why people choose to not use the parking brake. Do you imagine something bad will happen if you set the parking brake "unnecessarily"?

This is really the most important take away here. When I learned to drive, I learned to set the parking brake as a part of the procedure for turning off a car. It doesn't matter if you're on a hill or not. It also doesn't matter if you're in the country where nobody is likely to come steal your car - you should treat a car the same way you should treat a loaded firearm. If you are leaving it unattended it needs to be properly powered down and the key goes with you. As the owner of a car (which is a privilege, not a right) this is just basic safety responsibility. People need to be a little more aware that a car is not just an appliance to get you from A to B, but like any power tool is capable of causing great bodily harm or death if not treated with adequate respect.

I have been setting my parking brake since the beginning, have been teaching wife, kids, etc. but not once have I seen any of my dealer/mechanics set this brake. Heck, when I dropped my LEAF off 2 weeks ago, the service dude had trouble moving the car, because he couldn't figure out how to unset it. If the mechanics won't follow this practice, how can we expect most folks to follow this really important step (without folks such as us pushing others to set it)?

 

[klapauzius]

Seems like the most likely explanation is it was left in D and was held in place by the creep until the battery went dead. Then the LEAF switched to neutral and rolled back down the driveway. It may make more sense for the LEAF to instead go into park if the car isn't moving when this occurs though...

At least in theory, if the car is not moving i.e. creep and gravity cancel each other exactly, that should not drain the battery, as no energy is used?

How much Wh does the battery "boil off" in a night, when just sitting there?

Unless the car was very slowly moving uphill, and ran out of power...but that would have been noticed, as the driver would essentially get out of a moving vehicle?

 

[QueenBee]

Seems like the most likely explanation is it was left in D and was held in place by the creep until the battery went dead. Then the LEAF switched to neutral and rolled back down the driveway. It may make more sense for the LEAF to instead go into park if the car isn't moving when this occurs though...

At least in theory, if the car is not moving i.e. creep and gravity cancel each other exactly, that should not drain the battery, as no energy is used?

How much Wh does the battery "boil off" in a night, when just sitting there?

Unless the car was very slowly moving uphill, and ran out of power...but that would have been noticed, as the driver would essentially get out of a moving vehicle?

It can't fight gravity for free. If no energy was being used on a slope then it would roll back.

 

[DaveinOlyWA]

Seems like the most likely explanation is it was left in D and was held in place by the creep until the battery went dead. Then the LEAF switched to neutral and rolled back down the driveway. It may make more sense for the LEAF to instead go into park if the car isn't moving when this occurs though...

At least in theory, if the car is not moving i.e. creep and gravity cancel each other exactly, that should not drain the battery, as no energy is used?

How much Wh does the battery "boil off" in a night, when just sitting there?

Unless the car was very slowly moving uphill, and ran out of power...but that would have been noticed, as the driver would essentially get out of a moving vehicle?

It can't fight gravity for free. If no energy was being used on a slope then it would roll back.

no free lunch here. I wonder if the OP simply hit the power button twice and did not notice it? would not explain why the car rolled since killing the battery would not pull it out of park but who knows? its apparent there are conditions of the situation we are not aware of

 

[klapauzius]

It can't fight gravity for free. If no energy was being used on a slope then it would roll back.

Yes it can! Static forces, here gravity vs. electromagnetic and then traction, never consume energy!
Its basic physics, energy = force x distance.
Here the distance was presumably zero, as the car did not apparently move, so no energy expended.

Imagine it was different....We would have to power every bridge and building to prevent them from collapsing under the forces of gravity, stable planetary orbits would be impossible (without a significant energy source) , it would be the end of the world!

Of course, since some voltage over the motor is needed to keep up the electromagnetic force, there will be leak currents, so in reality, tiny amounts of energy could be used, but probably not on the order of kWH.

It is possible that just being on and in 'D' would draw enough power from the battery, that over 10 h it drains an already depleted battery?
The moment voltage on the motor goes to zero, traction force gets turned off, gravity wins and the car rolls backwards....

I am still stunned that the OP could basically exit the car while driving, not noticing anything.
But with keys inside, the car would not "know" where the driver was....

I wonder if there is a smart (and safe) way to determine if a driver is present and otherwise default to "P"?
E.g. check the driver seat weight sensor for some time in combination with any activity on gas/break/steering wheel?

 

[QueenBee]

It can't fight gravity for free. If no energy was being used on a slope then it would roll back.

Yes it can! Static forces, here gravity vs. electromagnetic and then traction, never consume energy!
Its basic physics, energy = force x distance.
Here the distance was presumably zero, as the car did not apparently move, so no energy expended.

Imagine it was different....We would have to power every bridge and building to prevent them from collapsing under the forces of gravity, stable planetary orbits would be impossible (without a significant energy source) , it would be the end of the world!

Of course, since some voltage over the motor is needed to keep up the electromagnetic force, there will be leak currents, so in reality, tiny amounts of energy could be used, but probably not on the order of kWH.

It is possible that just being on and in 'D' would draw enough power from the battery, that over 10 h it drains an already depleted battery?
The moment voltage on the motor goes to zero, traction force gets turned off, gravity wins and the car rolls backwards....

OK, next time you park on a hill put the car in neutral while someone pushes on it to keep it from rolling and tell me how easy that is for them and that they didn't expend any energy because the car didn't move. I guess you'll have to move from basic physics math to advanced physics math to calculate the amount of energy(electricity) required to keep a car from rolling using the motor. As to how much that is I don't really know. Is it really just a tiny amount?

Say they had 5kwh left in the battery. Just the cars system are probably not enough to drain it in 10 hours but add in climate control and it would be.

 

[HPJ]

WOW, after just reading this tread. I have come to the conclusion that most, it not all LEAF drivers really don't know how the LEAF operates under all conditions, situations, and scenarios, myself included. While I have not had any really weird things happen that I could not explain myself in my 3 years of ownership (I'm a careful driver and always keep my fob in my pocket), I can imagine conditions that could occur in which I could be clueless about ahead of time.

Therefore, I have to ask if anyone knowledgeable has seen or made (including Nissan) flow charts of the LEAF's operational modes under various conditions especially the ones mentioned (like TURN ON - OFF, with FOB in/out of car/with or without low battery, etc., etc.) anywhere? I haven't seen any, but I also have to admit that I haven't parsed or searched every page of all the manuals, or the forums.

I think comprehensive flow charts would be very valuable and much easier to follow and understand then trying to read explanations in a manual assuming any are provided.

 

[klapauzius]

OK, next time you park on a hill put the car in neutral while someone pushes on it to keep it from rolling and tell me how easy that is for them and that they didn't expend any energy because the car didn't move. I guess you'll have to move from basic physics math to advanced physics math to calculate the amount of energy(electricity) required to keep a car from rolling using the motor. As to how much that is I don't really know. Is it really just a tiny amount?

Say they had 5kwh left in the battery. Just the cars system are probably not enough to drain it in 10 hours but add in climate control and it would be.

Humans is a different story, but for the leaf motor it is simple, if it doesnt turn under load, its not using real amounts of energy.

Did the OP report that the car was drained empty the next morning? That would give some clue to this mystery.

 

[RegGuheert]

At least in theory, if the car is not moving i.e. creep and gravity cancel each other exactly,...

This part is exactly correct. In fact, since the motor in the LEAF is a synchronous machine with permanent magnets on the rotor, a permanent magnet (or a set of them) of sufficient strength placed in the proper location around the stator would hold the car from moving against gravity.

...that should not drain the battery, as no energy is used?

Only in theory, but not in reality. The difference is that the stator in the LEAF is an electromagnet which is commutated electronically.

So does that result in a not-insignificant amount of power being drawn? Using current technology, yes.

In order to produce an arbitrary stator current in one or more of the three phases of the stator from a fixed battery voltage, each side of the windings is switched between 0V and ~400V about 7000 times per second (the frequency is my guess). The duty cycle is controlled to allow the exact current desired to flow through the stator. This is an "efficient" approach which can deliver over 100kW while wasting only about 4kW or so. The problem is that even if no power is being delivered to the drive wheels, there is about 1kW consumed (wasted) by the motor, the inverter and various wires. There is also power wasted to run the cooling pumps and all of the other electronics in the LEAF.

How much Wh does the battery "boil off" in a night, when just sitting there?

In 10 hours, a LEAF in this condition likely will consume about 10kWh from the battery.

(BTW, the above is why the efficiency of the LEAF only increases down to a particular speed and decreases below that speed.)

I suspect in the future a car with capabilities similar the LEAF will be able to consume substantially less under similar conditions. I wouldn't be surprised to see this 1kW loss drop to about 200W or less in a decade or two.

 

[klapauzius]

The problem is that even if no power is being delivered to the drive wheels, there is about 1kW consumed (wasted) by the motor, the inverter and various wires.

:shock: 1kW??? So if I find myself in stop-and-go traffic, this is what is wasted when I put my foot on the brake?? Not exactly great engineering....
Anyway, that would explain how 5 kWH evaporate over night, the car shuts down and rolls down the hill

 

[johnrhansen]

The problem is that even if no power is being delivered to the drive wheels, there is about 1kW consumed (wasted) by the motor, the inverter and various wires.

:shock: 1kW??? So if I find myself in stop-and-go traffic, this is what is wasted when I put my foot on the brake?? Not exactly great engineering....
Anyway, that would explain how 5 kWH evaporate over night, the car shuts down and rolls down the hill

I would imagine the inverter quits sending power to the motor when the brake is depressed far enough. I think the only power drawn in drive with the brake depressed is enough to power all the computers in the car plus the heater or ac.

 

[gbarry42]

Did the OP report that the car was drained empty the next morning? That would give some clue to this mystery.

Yes, they did. Inasmuch as original post means top of page 1, we see

When we opened the door and noticed that it said extremely low battery and noticed the gear N (neutral) showing on dashboard. My husband said that I must have parked the car in neutral.

After which, I noted the LEAF does indeed go to N after the battery dies in D, but did not know if it would do that from P (sounds stupid, but no one has ever actually tried it).

Humans is a different story, but for the leaf motor it is simple, if it doesnt turn under load, its not using real amounts of energy.

Lest we believe the motor only uses imaginary amounts of energy, lets consider the physics. This turns out to be something of a riddle, since, as you say, force over zero distance equals zero work. As well as the fact that the parking brake does no work when holding the car on a hill.

Hmm, ponder, ponder.

Here's what I came up with. The battery provides current to create an electromagnetic force in the motor to balance the force of gravity trying to push the car down the hill. So far, so good. The problem is in the losses (you called this leakage). There is resistance in the wires, and there are switching losses in the inverter. If there were no losses at all (superconducting wires, etc), then you could take away the battery and let the current flow endlessly. But in the real world, we have to keep adding power to compensate for the losses. The "work" here turns into heat.

I think the surprise here might be how much power is consumed while holding still on a hill. I don't know for sure, and I will go find a hill and try it. After all, there's a power meter right there on the display.

By the way, right after I got a Prius, I was holding a hill using the throttle, and I happened to look at the energy gauge. And I saw it consuming power, and thus said, "oops", and then I stepped on the brake, and the power consumption dropped to zero. So, I learned something that day. (Never thought about it after that until you brought this up )

 

[DaveinOlyWA]

It can't fight gravity for free. If no energy was being used on a slope then it would roll back.

Yes it can! Static forces, here gravity vs. electromagnetic and then traction, never consume energy!
Its basic physics, energy = force x distance.
Here the distance was presumably zero, as the car did not apparently move, so no energy expended.

Imagine it was different....We would have to power every bridge and building to prevent them from collapsing under the forces of gravity, stable planetary orbits would be impossible (without a significant energy source) , it would be the end of the world!

Of course, since some voltage over the motor is needed to keep up the electromagnetic force, there will be leak currents, so in reality, tiny amounts of energy could be used, but probably not on the order of kWH.

It is possible that just being on and in 'D' would draw enough power from the battery, that over 10 h it drains an already depleted battery?
The moment voltage on the motor goes to zero, traction force gets turned off, gravity wins and the car rolls backwards....

I am still stunned that the OP could basically exit the car while driving, not noticing anything.
But with keys inside, the car would not "know" where the driver was....

I wonder if there is a smart (and safe) way to determine if a driver is present and otherwise default to "P"?
E.g. check the driver seat weight sensor for some time in combination with any activity on gas/break/steering wheel?

no no no... a bridge has cables that supply the force to prevent the bridge from swimming. a parking brake also provides force in a levering action to prevent movement. in the suggested scenario above, the creep force of Drive is negating gravity. eventually the battery runs down and shifts to neutral. the OP's contention that is was in park in NOT possible.

a power loss would have left it in park. we simply need to confirm this with the people who have taken the "flatbed ride of shame" and let them recount the issues they had getting the car on the bed