Plug-in on HV: running out of gas causes critical error

[Alexander Pournelle]

I should know better. (And apologies if this has been addressed. I don’t see a post on it.)

2019 Clarity Plug-in, 11,000 miles.

Executive Summary: Running past 6 gallons of use on the tiny Clarity Plug-In’s 7 gallon tank—Come ON, Honda, I’ve had Big Gulps bigger than that!!—was foolish, but it did give me a story, which I thought worth asking if anyone else had the error.

I was running in HV Mode, 28 miles Of indicated battery range left, trying to stretch to the gas station. The gas range was at zero (?!) for at least ten miles, though the engine never coughed. The car was running fine on battery so I didn’t think to switch to Eco mode.

As I exited the ramp, a big red warning came on the center console: “Critical Error. Stop your car safely and turn it off”, or something similar. I held my breath, as the beeping continued, but the car was running under power.

Rolled to the gas pump, pushed the “Start” (On/Off?) button, realized I had been holding my breath. Filled the car—7.1 gallons. Guess it was indeed empty.

Waited a minute, pushed Start. No more error. Selected HV mode, engine started without a cough; guess the injectors didn’t run dry, or this design fixed that problem. Completed my next hundred miles of driving, no further incidents.

The morals:
—Don’t try to stretch your gas range quite so much
—The 15 between Barstow and Las Vegas needs conventional chargers. The ChaDeMo and Combo chargers do nothing for most of us
—Try not to run on gas below “20” miles range. Yes, I gather the range estimate is a lie, but, still.
—Don’t Panic if you get a “Critical Error” Of this sort but do go fill up
—Honda needs to change that wording. “Critical”? C’Mon.

What say other owners?

 

[ClarityDoc]

While it seems to have turned out fine for you, I would not drive on with a "critical error - stop!" message displayed. Too much at stake. Hard to know what Honda should do to balance crying wolf versus protecting critical systems.

If someone runs across the freeway at night and doesn't get killed, that doesn't mean they made a good decision.

 

[Alexander Pournelle]

I was literally on the off ramp in 108 degree heat. I was going to get it as close to shade as I could.

If this was for running out of gas—and it sure seemed to be—it was never “Critical”, and saying it was doesn’t make it so, Honda.

 

[2002]

I was literally on the off ramp in 108 degree heat. I was going to get it as close to shade as I could. If this was for running out of gas—and it sure seemed to be—it was never “Critical”, and saying it was doesn’t make it so, Honda.

The message said to stop when safe. Stopping on an offramp in 108 degree heat would not be safe.



The computer may not have known exactly what the problem is, most cars only have low fuel warnings, they don't have a way to know exactly when the fuel runs out. Even if it knew or suspected that the problem was due to the already detected low fuel situation it may have still given the same message because according to the owners manual running out of fuel can damage the catalytic converter.

I was running in HV Mode, 28 miles Of indicated battery range left, trying to stretch to the gas station. The gas range was at zero (?!) for at least ten miles, though the engine never coughed. The car was running fine on battery so I didn’t think to switch to Eco mode.

HV mode uses gasoline. Any electricity that it uses from the battery during HV mode it immediately replaces through recharging. So as you continued in HV mode past the low fuel warning that you received probably about forty miles earlier and which was still on the display as you then continued past the indicated 0 HV range, you were using up the last gasoline in the tank. Turning off HV and going into EV mode (not Eco mode) would have stopped gasoline usage as long as you didn't do any hard acceleration.

 

[Alexander Pournelle]

In 2019, anyone who builds a fuel flow sensor which can’t detect lack of fuel should be dismissed from any engineering task more complex than making coffee.

This isn’t a 1972 Datsun 240Z. There’s no excuse.

And it didn’t run out or even cough. It stayed on gas the entire time.

If they detected the problem, why couldn’t the car correct it by going to EV?

 

[Lowell_Greenberg]

In 2019, anyone who builds a fuel flow sensor which can’t detect lack of fuel should be dismissed from any engineering task more complex than making coffee.

This isn’t a 1972 Datsun 240Z. There’s no excuse.

And it didn’t run out or even cough. It stayed on gas the entire time.

If they detected the problem, why couldn’t the car correct it by going to EV?

My guess is that if the car was running in normal or eco mode It would have gone on, if needed, on battery power. Your experience, assuming it was not due to other factors besides running out of fuel, illustrates one drawback of not allowing the car to choose it's own mode by bypassing normal mode. This is reinforced by the fact that the car allowed you to run out of gas in the first place with available charge.

Sent from my SM-G975U using Tapatalk

 

[MrFixit]

@Alexander Pournelle - Your actions after the critical warning seem perfectly sane to me !
I agree there is a distinction between an inexplicable critical warning, and one where you are 99% certain what is going on.

Just curious... You didn't mention the fuel warning light. How many HV miles were indicated when the warning light came on? I tend to use the warning light as an signal to start looking for a gas station (well, there are lots of stations in my area)...

 

[David in TN]

Having had the same experience, I had no issues, other than the same messages that you had.

When low fuel appeared, I reset trip B. According to the manual, there is 1.1 gallon left. In HV mode, showing 42 mpg, I hit an exit at 46.2 miles and the lights lit up. I had about 20 miles of EV left. I went the last 0.5 mile on EV, then filled up. No issues upon restart.

Sent from my SM-N960U using Inside EVs mobile app

 

[fotomoto]

I did over 30 miles highway after reaching zero remaining in HV mode; had about 30 miles EV for backup. Never did get the critical error message before reaching the station and filling up with 6.97 gallons.

 

[css28]

So would the OP prefer a critical error message after the system damages itself?

 

[craze1cars]

What say other owners?

I say much ado over nothing. Doesn’t really matter if anyone likes the wording on the dash. After ignoring earlier low fuel light, the car was now stepping it up a notch and warning you it was within a certain distance of shutting itself down. Kinda thoughtful to have a 2nd more aggressive warning IMO. Most cars don’t do this when you’re about to run out of gas...most just sputter our. It can’t read your mind on how soon you intended to stop and fill.

So then you filled up and carried on. Warnings cleared. Car and humans all happy.

All makes sense to me. Next time buy gas sooner.

 

[Mowcowbell]

Was down to 1/2 tank of petrol in the Honda Clarity, so I filled it up. Took 3.42 gallons of 100% gas (87 octane) for a total cost of $8.01.
Last time I filled it? June 17th. Gotta love the Clarity!

 

[2002]

In 2019, anyone who builds a fuel flow sensor which can’t detect lack of fuel should be dismissed from any engineering task more complex than making coffee.

This isn’t a 1972 Datsun 240Z. There’s no excuse.

You probably need to expand the complaint to all cars that only give a low fuel warning but don't later give a message stating that you have now actually run out of gas.

Although it does seem Clarity does have a message that occurs when you actually run out of gas:

"Engine System Problem. Power Generation Not Available. Vehicle will stop in X miles."



There is a video posted by someone who purposely ran their Clarity out of gas and kept driving. He says he got the "Vehicle will stop in X miles" message after he ran out of gas, and he said the miles shown in the message was the same as his EV range at the time. In the video he says that he only got the critical, stop driving when safe message after his EV range got down to 0.

https://insideevsforum.com/community/index.php?threads/empty-tank-and-dead-battery-test-video.6684/

If they detected the problem, why couldn’t the car correct it by going to EV?

If you did actually run completely out of gas and you were still driving, then it was essentially in EV propulsion mode even if the HV indicator was still on.

 

[victor_2019]

If this was for running out of gas—and it sure seemed to be—it was never “Critical”, and saying it was doesn’t make it so, Honda.

Actually it was critical and the fact that you stopped in time before any damage was done doesn't mean the warning is wrong.

Don't assume you know more than the designers of the car.

If you discharge a lithium ion battery too much you destroy the battery.

When you get too low on electric charge the engine will start. If you have no more gas, only two things can happen:

Either you keep driving until your battery is ****ed and then it will cost you who knows how much to replace it, or

The car shuts down to protect the battery meaning you can suddenly lose power and control of the car while driving at high speed on the highway.

Neither choice is very good. So yes, it's very ****ing critical that you safely stop the car and shut it down.

 

[css28]

I've read of people doing that to Prius cars over the years. In each case, after running out of gas assuming that they can EV it the last couple of miles to the gas station.
The car will let them do it because Toyota won't risk shutting the car down but the car can't crank the engine once the traction battery is truly depleted. For most of the Prius cars this is a NiMH battery though.

 

[JCA]

I'm sorry, but there's no way the battery system is going to be damaged in any way by running out of gas and continuing to drive. The car is designed to gracefully reduce and then shut off the battery output with the proper buffer remaining. From the experiment done on video in the other thread (https://www.insideevsforum.com/comm.../empty-tank-and-dead-battery-test-video.6684/), the battery behavior is exactly the same as when you run out of EV range normally -- the threshold of the engine coming on gets lower and lower (as shown by the blue bar) until you can't even go a few MPH on battery alone. The only difference is that with no engine to come on, the car just doesn't accelerate beyond that minimal to no amount.

The engine system, likewise, is unlikely to be damaged by running out of gas -- some old cars did have the fuel pump keep running (without cooling with no gas in the tank) indefinitely while the key was "on", and many people when stalled and flustered might not notice/think to turn the car off. The Clarity computer knows exactly when the engine is on and off, and I'm 100% sure would not leave the pump on with no engine response. I also don't really buy the sludge argument (unless the concern is floating debris, any sunk debris is either going to be sucked in anytime or not), or a one-off misfiring causing permanent damage.

I believe the reasons this is considered "critical" are:

1) Without the engine, at best you have a little less power available than you expect; at worst a lot less (when close to 0 EV). Imagine pulling out onto a main road in front of an 18 wheeler and not having the acceleration you expect (or stalling right there) -- and imagine Honda's liability concerns.

2) When the car does run out of battery on the highway, it'll be fairly quick and you may not have time to get safely off. And without the warning, it'd be easy to not even realize that the engine had stopped. We're used to being able to just drive beyond 0 EV without thinking about it.

The wording of the warning is pretty clear to me -- Power Generation (the engine) is not available, and you have X miles to go. Critical that you know because of the above reasons, but not critical as in "stop in the lane or dive to the shoulder and flee the car immediately".

 

[2002]

The wording of the warning is pretty clear to me -- Power Generation (the engine) is not available, and you have X miles to go. Critical that you know because of the above reasons, but not critical as in "stop in the lane or dive to the shoulder and flee the car immediately".

I agree, the first message simply tells you that the car will stop in X miles, it doesn't tell you to stop. And the later "critical" message says only to stop driving when safe.

2) When the car does run out of battery on the highway, it'll be fairly quick and you may not have time to get safely off. And without the warning, it'd be easy to not even realize that the engine had stopped. We're used to being able to just drive beyond 0 EV without thinking about it.

Another good point and probably the reason for the seriousness of the message.

I'm sorry, but there's no way the battery system is going to be damaged in any way by running out of gas and continuing to drive.

Certainly just running out of gas won't damage the battery, the comments were about then continuing on past 0 EV range, which the car will continue to do since there is 10% SOC below 0 EV range. However it is not common for the battery to dip below about 7% in normal operation so running it down to 0% may not be good for it. Whether that is considered "damage" is semantics, I agree even running down to 0% SOC won't kill the battery since there is plenty of reserve even below that, but there is no way to predict long term effect on battery life.

The engine system, likewise, is unlikely to be damaged by running out of gas

Without rereading the thread I don't think anyone said the engine will be damaged, however the manual states that running out of gas can cause engine misfiring which can damage the catalytic converter. Now whether the chances of that happening are one in 10,000 I have no way of knowing, but the other part of it is that any damage to the catalytic converter would not be readily apparent. So there is no definitive way to know if those who say they have run out of gas and no harm was done are correct.

 

[JCA]

Certainly just running out of gas won't damage the battery, the comments were about then continuing on past 0 EV range, which the car will continue to do since there is 10% SOC below 0 EV range. However it is not common for the battery to dip below about 7% in normal operation so running it down to 0% may not be good for it. Whether that is considered "damage" is semantics, I agree even running down to 0% SOC won't kill the battery since there is plenty of reserve even below that, but there is no way to predict long term effect on battery life.

I agree -- my point is that the car isn't going to let the battery get to 0% in any case. From my driving experience and the video, "continuing on past 0 EV" works exactly the same whether you have gas or not as far as the battery is concerned. At and even below 0 EV the engine doesn't automatically come on; it just reduces the threshold lower and lower. If you're driving at arterial or highway speeds that does mean it comes on immediately, but you can drive slower and slower and stay "EV". I got to 0 EV as I entered my neighborhood a while ago (with plenty of gas), and I was curious so I kept driving around at low speed keeping it below the ever-lowering blue bar. I was able to eek out another mile or so like that, accelerating very very slowly off of stop signs (no other cars around) until the engine finally came on at the slightest touch. That would be the equivalent of when the video taker with no gas went slower and slower until the car just wouldn't go any more.

I was driving like that on purpose, but it could have easily been natural depending on the road, traffic etc. I am confident that the computer won't allow the battery to be damaged in that scenario that's entirely expected in a PHEV. It's not like going slow "tricks" the computer into allowing it to drain to a true 0% damaging level ("hey, I didn't notice we were moving!"). I don't think I had Torque logging that time, but will experiment again when I can and report back on the actual SOC it gets down to.

 

[css28]

To clarify (in my comment #15) some who ran their Prius cars dead after running out of gas would have to have their car towed to a Toyota dealer to get the battery pack resuscitated.
These cars lost the battery charge to crank the engine.

 

[2002]

I agree -- my point is that the car isn't going to let the battery get to 0% in any case. From my driving experience and the video, "continuing on past 0 EV" works exactly the same whether you have gas or not as far as the battery is concerned. At and even below 0 EV the engine doesn't automatically come on; it just reduces the threshold lower and lower. If you're driving at arterial or highway speeds that does mean it comes on immediately, but you can drive slower and slower and stay "EV". I got to 0 EV as I entered my neighborhood a while ago (with plenty of gas), and I was curious so I kept driving around at low speed keeping it below the ever-lowering blue bar. I was able to eek out another mile or so like that, accelerating very very slowly off of stop signs (no other cars around) until the engine finally came on at the slightest touch. That would be the equivalent of when the video taker with no gas went slower and slower until the car just wouldn't go any more.

I was driving like that on purpose, but it could have easily been natural depending on the road, traffic etc. I am confident that the computer won't allow the battery to be damaged in that scenario that's entirely expected in a PHEV. It's not like going slow "tricks" the computer into allowing it to drain to a true 0% damaging level ("hey, I didn't notice we were moving!"). I don't think I had Torque logging that time, but will experiment again when I can and report back on the actual SOC it gets down to.

At 0 EV it acts the same as if you had 40 miles EV range and pressed the HV button. I am making a general statement as it would take a lot of SOC monitoring to see if there are any subtle differences in how HV mode works at different levels of SOC, but general speaking HV mode at 0 EV range works the same as it does at higher SOC. At 0 EV range you are at 10% SOC and just like in any other HV situation it works like you describe and will at times shut off ICE especially at slow speeds, or even on the freeway when on a slight decline. But it won't go on battery only for very long because it wants to maintain SOC, just like regular HV mode. Normally I only see it go down to about 8% but sometimes down to 7%. Unless you have seen lower.

The only time I have seen SOC drop lower than 7% is when running AC while parked with 0 EV range. In that case it does not turn ICE back on until you get down to 1%. It then charges up to about 2% sometimes 3% then shuts off, until you get down to 1% and the cycle keeps repeating. Even though the car allows this I am not convinced it is good for the battery and once I realized it was allowing SOC to get that low I never sit parked with AC on unless I have some EV range. As you probably know remote climate won't turn on if EV range is too low, in theory they could run it down to 1% like happens when sitting in a parking lot with the system on, but it won't even start remote climate if you are close to 0 EV range.

EDIT - I somehow missed this part:

From my driving experience and the video, "continuing on past 0 EV" works exactly the same whether you have gas or not as far as the battery is concerned.

It would certainly work different without gas because when the SOC drops below 7 or 8 percent it would want to start ICE to get back to the target but it will not be able to. It is no longer able to run in charge sustaining mode like it normally would and can only run in charge depleting mode. Thus taking SOC much lower than it normally would. Bad for the battery? Maybe. How bad? Who knows, probably nothing you would immediately notice it's just an unanswerable question about battery life.