Six miles, Low Battery Warning to Turtle (Sans Effect)

[cwerdna]

If only Nissan would allow tow charging like those Dutch guys did.

It might take a bit less time and serve 2 purposes: getting you partway to your destination and providing you a bit of juice so that they don't need to tow you all the way.

Where do they prohibit that? They don't. If the truck had a portable DC quick charger, like AAA is supposed to have, the car would have plenty of miles in the time it took to load it up.

Actually, I doubt AAA will have QC, and if you let the car automatically shut down in Turtle, it takes a LONG time charging on L2 before it will restart.

Heh, well, I don't think Nissan's recommended it and there might be some liability or safety issues w/doing so, esp. if one needs to/should remain in the tow vehicle to press on the brake pedal while being towed.

Actually, since you mention AAA w/QC, that would also depend on the Leaf having a QC port.

I'm w/gbarry42, if there were doubts that I could make the trip or I had to make all these stops to opportunity charge just to make it, I'd be taking my Prius instead. FWIW, bwilson4web over on Priuschat has intentionally run his Priuses out of gas dozens of times as part of some of his gasoline testing + other testing. But yeah, people on Priuschat will scold those who run out by of gas by guessing they have the full 11.9 gallons of gas available (on the 2nd gen) and multiplying by their indicated mpg or thinking they have xx miles left when on the last flashing pip. That's a recipe for disaster.

 

[Herm]

Maybe the low temperature voltage sag confused the BMS into thinking the SOC was lower than the actual SOC. This would explain why after some time off the estimated SOC was higher so no turtle mode to enter the tow truck.

I was thinking that too, perhaps a GID meter would have shown a recalibration after the car shutdown and reset.

 

[DaveEV]

My 2 cents:

You charged for 3 hours after your first VLB and expected to drive 38 miles? I guess if you're counting on 6 miles after VLB that's OK, but certainly cuts it to the wire.

Let's assume that you charged at 3.8 kW at 85% efficiency, so you get 9.7 kWh in the car. Now to get 38 miles you need to average at least 3.9 mi / kWh on the dash and probably should keep it at 4.0 or higher. Did you? It's pretty clear that one should not expect to get very far after VLB.

Also, I wouldn't call ~2 hours of charging from 80-100% a lot of time for cell balancing, unless you left it plugged in the whole time?

Certainly the theory that multiple partial charges in the day leaves the SOC meter a bit confused makes sense since it's hardest to determine SOC accurately in the middle of the SOC. It would have been interesting if you had shut down after immediately hitting turtle (or noticing power bubbles go away) and let the pack "rest" for 5-10 minutes if it would have recalibrated itself better. How hard were you driving once you got to the LBW and beyond?

 

[GRA]

I wonder if Tony is starting to see the effect of all the deep discharges he's done. He's sort of done beta testing for everyone, torturing the battery so the rest don't have to. ISTR he said he was leasing; I sure hope so.

I may well change the requirement in my "worst case" range thread to staying out of LBW instead of VLBW, instead of making it optional. My personal reserve in an ICE is at least 10%, with a minimum of 10 and a normal maximum of 30 miles - it can be a lot more off the interstates if I'm seeing 'Next Gas XXX miles' signs. Certainly, any time the low fuel light (IIRR 1.4 gal remaining) in my Subie comes on I'm thinking about gassing up rather than trying to make it, even though I know I can go at least another 30 miles with no problem.

 

[TonyWilliams]

First, let me say that I don't care what Hummer drivers think or do, I don't have a spare Prius to drive. I don't care whether others do or do not use the full potential of the car (with the extremely benign consequences of it not working). Based on the predictable nature of the previous 12 Turtle events, this 13th event is atypical.

When the navigation said I had 12 miles to go, I got LBW. That is right on schedule for the 60mph I was driving in 62F air (meaning the battery was probably 70F at least). Everything up to this point was as expected and planned. I was running the heater, so that was switched off, post haste.

But, there's the rub. If I can't plan to use the (very limited) predicted range 100% of the time, it's just another issue that the car isn't quite ready for prime time. GM seems to have went the extra mile on the Volt to mitigate this.

Anyway, as soon as I got LBW, reduced the speed to 50mph, cleared the message, and reset the trip odometer. I still fully intended to, at the least, be walking distance from the intended destination, as I have so many times before, based on historical empiracle data.

Yes, I have known about other cases of this similar to this event. My impetus for sharing is so that we can learn and understand how we can be warned of a similar instance happening again.

 

[surfingslovak]

I wonder if Tony is starting to see the effect of all the deep discharges he's done. He's sort of done beta testing for everyone, torturing the battery so the rest don't have to.

While certainly possible, I really hope that this is not the case. Tony had his Leaf for less than a year, and although he might be stressing the pack more than the average owner, let's hope that it's robust enough to sail through the first 2-3 years of ownership. I think that we'll see cell failures, which will necessitate replacement of battery modules, but that should not happen during the first or second year of ownership. I'm basing this projection on what I've gleaned from the Tesla forum; I hope that AESC cells are more robust than the laptop cells used in the Roadster. On the other hand, I'm really impressed that Tesla can predict cell failures in advance and perhaps even remotely.

 

[TonyWilliams]

I wonder if Tony is starting to see the effect of all the deep discharges he's done. He's sort of done beta testing for everyone, torturing the battery so the rest don't have to. ISTR he said he was leasing; I sure hope so.

Except, this same issue has happened on cars that likely weren't as frequently fully cycled (and probably not pushed very hard at all).

If this is a cell failure of some kind, it will be repeatable. If not, it won't have much impact on me driving.

We seem to always be looking for that first sign of battery deterioration, but I predict those issues will be more like the frog in a slowly warming frying pan....

I think I'll probably not keep this LEAF long term, and will replace with a Tesla or other longer range car (maybe the Rav4 will work, assuming it has QC).

 

[TonyWilliams]

If you are in the wrong place, the warnings are of little use because you will be stranded. While in such a place, actually with more than enough charge to get home, I pondered what I would do if I did have a low charge. My thought was that the thing to do is find any place with a 120 volt outlet and depend "on the kindness of strangers". Gas stations and convenience stores seemed like the best possibilities.

I was actually in an area with few exits and no civilization. Believe me, I was thinking all the options, but from the first sign of trouble to Turtle was less than 2 miles.

 

[TonyWilliams]

On a second note.. if I KNEW my battery was dangerously low and I wasn't going to make it to my intended place to charge, I would pull off the road and find a parking lot somewhere. With any luck I could find a 120V outlet somewhere to charge for an hour or two. But even if I had to call a tow truck, I'd rather be towed away from a parking lot than have the general public see a Leaf being towed from the side of the highway because it ran out of juice. That is exactly the type of thing the general non-EV accepting public is afraid of. I bet all of the Hummers and F250 dually's driving by were laughing.

Lots of armchair quarterbacking there chief. There was no spare parking lot on the 57 freeway, nor 120v plugins, sorry. As I stated in another post, the distance traveled from the first sign that something wasn't kosher, until Turtle, was less than 2 miles.

While you may feel that you need to hide from Hummer and "Dually" drivers, that doesn't, and will not, enter into my thoughts. Actually, it seems kind of childish.

 

[TonyWilliams]

Unless you happen to be driving in flat terrain, gauging charge remaining by "miles" is an exercise in futility.......
Never seen the turtle, and not planning to.

I never quite get these posts; "I've never done it, but it can/can't be done".

Ok. Thanks.

 

[evnow]

Interesting tid-bit. I restarted the car and drove it to the back of the truck. Car did not show Turtle mode anymore. Started it again and drove it into the charging spot; again, no Turtle.

May be something to do with what the Nissan engrs said - that when you switch off is when the BMS can more accurately figure out the SOC level ?

 

[vegastar]

There was one day where I did lots of partial charges and in the return home at 60mph from LBW to VLBW I did only 4 miles with a net loss of altitude. That scared me but fortunately I was 2 miles from a Quich Charger and made that distance slowly (20-30mph). I tought it could be the temperature getting lower (10ºC, 50ºF) but it could be the BMS not figuring out the charge under the constant load I was giving the car.

I notice that sometimes after driving steadily for 20 minutes at 60-70mph, when I stop the SOC-meter jumps 1 or 2 % up or down. It could be that the coulomb counting is not very effective and only when the no load voltage is read the BMS calibrates its estimated SOC.

For the Volt is easier to have a very precise DTE, because the real SOC never goes so low as the LEAF (I think it only uses around half of the 16kWh?). It could even discharge a little more the battery just to keep the DTE accurate...

 

[surfingslovak]

For the Volt is easier to have a very precise DTE, because the real SOC never goes so low as the LEAF (I think it only uses around half of the 16kWh?). It could even discharge a little more the battery just to keep the DTE accurate...

I thought so too, but it's 10.4kWh, i.e. 65% ratio of usable to rated capacity, for the Volt. And unlike Nissan, GM apparently disclosed this figure publicly.

Now GM finally admits the Volt will actually use 65% of the total energy storage capacity of the battery. That amounts to 10.4 kwh. The engine generator will turn on once the battery hits somewhere between 20% and 25% state of charge, which equates to 25 to 50 miles of EV driving. When fully recharged, the battery will acutally be kept at a maximum 85% to 90% state of charge.

 

[garygid]

Tony,
Including your first roughly 15 or 20 data points (total maybe 35 near-Turtle experiences now), this is your third "atypical" shorter0tgan-expexted-range experience, right?

I sure wish we could get a dealer to use their Consult III machine to give us a printout of all 96 cell-pair voltages ... to see if one cell-pair is unexpectedly lower than the others.

But, glad you are safe.
Merry Christmas, Gary

 

[TonyWilliams]

Gary, this is the first instance "like this". Turtle 13 times, but near Turtle dozens of times. As you probably recall, I drove the 78/15 freeways 22 miles total from LBW to Turtle. You are no doubt referring to the first two times I turtled it, and had no idea what I was doing. Both times, I came up short and walked half a mile once, and 100 yards the second time.

With that said, again, this is an unplanned event, and the only of it's kind for me. My strategies are to plan the range, and adjust the speed for any variations in the range once underway. This trip was planned at 60mph.

Bottom line; this is the exception that makes almost 10% - 20% of the bottom of the battery just dependable enough to lure complacency ;-)

What can we learn? If it's cell balancing, we need a way to warn of an out of norm condition. Or, like I warn in the notes on the range chart, be cognizant that the possibly exists, even if one time in dozens, that things will be significantly off in that bottom 20% of the battery (remember, it didn't deliver "book" performance from even the first battery warning at 17% SOC.

 

[downeykp]

Tony, I for one, appreciate that people like you have big enough balls to push the envelope. How are the rest of us to know what to expect if no one is willing to push the limits of the car. I am sure Nissan has a lot of data about what is being discussed here, but they do not seem to be willing to part with their knowledge. Again thanks Tony and Happy Holidays.

 

[DaveEV]

When the navigation said I had 12 miles to go, I got LBW. That is right on schedule for the 60mph I was driving in 62F air (meaning the battery was probably 70F at least). Everything up to this point was as expected and planned. I was running the heater, so that was switched off, post haste.

I'm still a bit confused as to what exactly happened:

So you had 4 bars and left at 60 mph w/the heater on expecting to get 28 miles. Assuming flat ground according to your chart, you should be able to get a 30 miles in 70*F at 60 mph with no HVAC. Not sure how much power the heat was pulling, but unless you were going downhill, it seems a bit optimistic. How quickly did you lose bars 4, 3 and 2 compared to how much distance you traveled? Going backwards from your notes, it appears that you went 16 miles before LBW (1 bar nearly all the way gone) and 20 miles before VLB.

But, there's the rub. If I can't plan to use the (very limited) predicted range 100% of the time, it's just another issue that the car isn't quite ready for prime time. GM seems to have went the extra mile on the Volt to mitigate this.

The Volt has the benefit of a range extender - there's no issue with draining it since you always have backup.

My impetus for sharing is so that we can learn and understand how we can be warned of a similar instance happening again.

Yeah - range estimation is difficult as you heard first hand from Nissan Engineers the other week. Nissan got it right for you 12/13 times - pretty good!

I regularly eat 5 bars on a 23 mile commute where I get 4+ mi / kWh. I can't say I'd venture a nearly 30 mile trip with only 4 bars showing on the highway running the heater.

 

[TonyWilliams]

You got the basic data right. Again, I likely would have made it had the batteries / instrumentation performed as it had previously dozens of times.

If I had projected coming up short a mile or three from LBW, I could always (previously) adjust speed from that planned to compensate.

I may have even made it had I known ahead of time that there was a condition that would prevent the planned performance.

Hitting the 12 mile to go mark at LBW was perfect. Any speed below 60mph should have been possible. The heater is not a factor, as I turned it off at 12 miles, AND lowered the speed.

Temps for this leg were low 60s, with heater previously on 68. Not much draw ( plus preheated during previous charge).

The bottom line; something is SIGNIFICANTLY different from every other time. Hopefully, most folks can understand a variation, but this was 50%+ reduction in range historically from LBW.

That is the issue.

 

[Herm]

While you may feel that you need to hide from Hummer and "Dually" drivers, that doesn't, and will not, enter into my thoughts. Actually, it seems kind of childish.

You know they are going to take pictures with their phones.. at least carry a tarp so you can cover up your shame.

 

[TangoKilo]

Just like in airplanes... There are those who have and there are those who will....