Empty tank and dead battery test video

Discussion in 'Clarity' started by KK Mui, Sep 1, 2019.

  1. KK Mui

    KK Mui New Member

    This guy took his Clarity gas tank to empty then kept driving until absolutely no juice left, brave soul:

  2. KentuckyKen

    KentuckyKen Well-Known Member

    IMHO, not brave but foolhardy.
    Forcing a depth of discharge that large past what the BMS is trying to keep can’t be good for his battery pack. Over charging and over discharging are killers for Li-ion batteries. I would not want to buy his car used. It would, however, be interesting to know the % SOC from his Honda Link and what his Battery Capacity Amp hrs are after that stunt.
  3. petteyg359

    petteyg359 Well-Known Member

    Clearly he hasn't gone far enough. The lights on the dash are on, so he hasn't killed the 12v battery yet.
    K8QM likes this.
  4. insightman

    insightman Well-Known Member

    After this driver added a gallon of gas, it appears his Clarity used some of the ICE power to restore one bar of HV battery charge. It was desperately trying to protect that HV battery! I wonder what OBDII codes were stored to record this event?
  5. sniwallof

    sniwallof Active Member

    High risk test (probably not a good idea, if nothing else, never a good idea to run a fuel pump dry), still good to know one might make it to a gas station within 10 or so miles in this worst case scenario. He talked about minutes running at one point, did he ever give us the total miles driven after an actual "0ev/0hv"? (engine stopped running all together from fuel starvation, numerous warnings)

    Funny, part of me is thinking, really-really stupid. But, I have to admit, I am also glad to know what to expect following a 0/0 scenario.

    I vaguely remember something about just adding a gallon to a few gallons not extinguishing the low fuel light (e.g. for folks who wanted to drive around with just 1 to a few gallons as was common for local Volt driving). Is it still the case that the Clarity just likes to be filled up for all indications to track properly? Wasn't there a time where just adding a gallon or two seemed to make no indication? OTOH, the Clarity gas level indicator bars time lag after fill up is also long and well known (e.g. immediately after a highway stop refill), probably just the software integration (averaging, time constant) to give a stable fuel display.
    Last edited: Sep 2, 2019
  6. fotomoto

    fotomoto Active Member

    With zero miles (no bars) indicated on the fuel gauge, I continued to drive over 30 miles in HV mode. That was nearly 50 miles since low fuel warning came on at 20 gas miles indicated left. Filled to only 6.972 gallons. I had been driving very fast in HV mode all day on the interstate so I think the estimator was getting more and more pessimistic. It only indicated an estimated 267 mile range after the fillup! ;)

    Last edited: Sep 2, 2019
  7. sniwallof

    sniwallof Active Member

    So, there are multiple low fuel scenarios, 30 to 50 miles from low gas indications (possibly ~50 from low hv fuel indication, possibly ~30 from "0" displayed hv range) @fotomoto (which is helpful). I say possibly, because the actual miles remaining in an individual situation may depend on recent driving speeds before going low and the guess-O-meter.

    But, then, there is apparently another 10+ miles still doable after gas fuel starvation (engine no longer runs, not good (abnormally low SOC, dry fuel pump), the video), using the last bit of traction battery charge that the Clarity will allow.
    Last edited: Sep 2, 2019
    fotomoto likes this.
  8. petteyg359

    petteyg359 Well-Known Member

    The only time I had zero gas bars, it filled with a little over 6 gallons, so I'd guess the gauge goes to zero at about 1 gallon left in the tank.
    MPower likes this.
  9. 2002

    2002 Well-Known Member

    Certainly risky but we really don't know how low the battery got, even if he was monitoring SOC we wouldn't know for sure. I think it's possible that at 0% SOC the car refuses to use the battery, in which case the battery would probably not be damaged since we believe that there is quite a bit of unused battery below 0%. Now certainly don't go out and try it for yourself I'm just saying we don't know for a fact that he damaged his battery by doing this. Of course even it didn't damage it, doing this regularly is likely not good for long term health of the battery, but that would be a similar question to sitting parked with the AC or heater running with 0 EV range, which brings SOC down to about 1% before ICE starts up to recharge the battery. What we don't know is how far below that the battery went during his stunt, since he probably started with the normal 8-10% SOC that you have at 0 EV range.

    I think he made a wrong assumption at the end when he put a gallon of gas in the tank while the battery was still unavailable, when he floored it and barely got it past twenty mph he assumed this was all the power that the gas engine has on its own, but I think more likely it was in some type of limp mode which allows you to move the car safely off the highway but not drive.
  10. KayakNate

    KayakNate New Member

    Hi. This is my vid. I just want to clarify that I did not get 10 miles after full gas starvation and 2 bars of battery. I got 3 miles/about 10 minutes of slower driving with AC. My range on charge has not been affected by this. I agree that this may have caused long-term damage to battery, fuel pump, etc. But the way the car transitioned from full power, to low power, to just not letting me use any power at all, felt very controlled. It seemed the car was still protecting a safely low amount of voltage from getting any lower. But again, that's just an assumption based of the way it was acting and that I have the exact amount of usable battery range available for my commute after testing.
    chris5168, Pegsie, 2002 and 1 other person like this.
  11. JCA

    JCA Active Member

    Thank you for experimenting, and for posting the results! I like to believe the car is smart enough not to damage itself, but *someone* has to try it :) Just like I had to see for myself what happens when you accidentally press a shift button while moving (at low speeds it gracefully slows and moves from Drive to Reverse and back; at high speeds it switches to Neutral).

    I wouldn't expect any damage to the battery system from running out of charge, the car handles that already by switching to gas every time you go to 0.0 EV. Reducing the electric power available until there's none is exactly what happens then too, just that the engine comes on to take up the slack.

    Running the gas engine dry, sure, *might* cause issues. But the "burning out the fuel pump" thing seems like an old wives/old cars tale from what I have found -- in some (much?) older cars, the engine would stop but the fuel pump would keep running indefinitely until you turned off the key, which you might not think to do while stranded on the side of the road. Running the pump for minutes/hours uncooled, sure, but briefly isn't going to burn it up. The Clarity engine isn't tied to the ignition key, and if it's smart enough to throw up warnings, it's surely smart enough to stop the fuel pump. And any sludge that could get sucked up when the fuel is low could get sucked up other times too. Same with injectors/timing, I find it hard to believe that misfiring a few times is going to permanently damage anything. I wouldn't want to do it regularly, but I suspect running the tank dry once or twice isn't going to hurt any modern car.

    The reason the car flashes up all the warnings is because some of the rated power comes from the gas engine. If you floor it (past the detent) expecting to beat that 18 wheeler approaching the intersection, you won't have the expected power. And, of course, while fairly graceful at the end of battery charge if you were driving 70 on a highway with limited shoulders you may not be able to safely pull off when you first start really losing power. Experimenting on local no-traffic streets like in this video is a lot less risky.

    I went 10 miles past 0 HV last time; then I chickened out and filled up with 6.8 gallons. Maybe watching your video will satisfy my curiousity so I don't feel the need to do it myself. Maybe :)
    MPower likes this.
  12. Phil_Meyers

    Phil_Meyers Member

    So if you were to charge it up full with an empty gas tank does it still drive normal than?
  13. Phil_Meyers

    Phil_Meyers Member

    I wouldn't expect any damage from using the battery to this low level. I would definitely assume Honda puts in a good buffer to protect the top and a good anti-brick buffer at the bottom end of their batteries.
  14. Geor99

    Geor99 Active Member

    Man, that guy looks like he is deliberately trying to destroy his vehicle!!!!

    Maybe he's trying to get a new battery under the battery warranty down the road:)
  15. 2002

    2002 Well-Known Member

    Or he had full confidence that the system will not let you destroy your vehicle by running out of both gas and battery. However most of us are glad that someone else decided to try it :)
  16. fargledaer

    fargledaer New Member

    A one time deep battery discharge like this is not going to do any noticeable damage. If you ran it like this every day, you would eventually be able to measure a significant capacity decrease after tens to hundreds of charge cycles depending on the battery specifications and exactly how low the state of charge gets before the car self-terminates.
  17. su_A_ve

    su_A_ve Active Member

    Cars are designed to assume you may run out of fuel. Range estimates in our '12 Ody would only give about 10 extra miles. I almost ran out of fuel once at 10 miles after zero. Our '18 Ody on the other hand starts alerting you much sooner than in the past.

    I would not be surprised our Clarity is designed to take into account the possibility of an empty tank and empty battery situation. Not sure if the owner who took the video measured how much charge it added after this stunt. I'm sure fuel added was very close to 7 gallons. But electricity?
  18. insightman

    insightman Well-Known Member

    That's why I wondered if the Clarity stores any codes relating to this behavior.
  19. 2002

    2002 Well-Known Member

    But they can't make it 100% certain that there will be no damage when you run out of gas, that's why they have warnings in the owners manual telling you not to. The only way to absolutely guarantee no damage is if they determine the lowest possible point that the fuel sensors are accurate to and then shut off the car when it reaches that point, of course after the standard warnings prior to this.

    However it seems to be almost a constitutional right to be able to push it all the way to the bitter end if we choose to and not have some uppity computer shutting things down when we are just a tenth of a mile from the gas station and we know deep in our bones that there are still a few drops left.
  20. out of gas-1.jpg Out of gas - 2.jpg

    FWIW - here are the actual messages that you get when you run out of gas. (apparently, it also leaves dust on the instrument panel, as well!!!)
    Last edited: Sep 14, 2019
    chris5168 likes this.

Share This Page