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Re: Nissan Engineering Team Visit Dec. 3rd: Recap

Posted: Wed Dec 07, 2011 11:11 am
by Herm
JohnOver wrote: How about a modification of that thought... When the car starts up it uses a long-term average (2 weeks?). It then uses the same algorithm that it uses now for the rest of the driving cycle.
Sounds simple enough, use a long term average for the first 10 minutes of driving when you start up the car.. best would be if we could switch among a few options.

Re: Nissan Engineering Team Visit Dec. 3rd: Recap

Posted: Wed Dec 07, 2011 12:57 pm
by DeaneG
My first thought was to use the last roundtrip efficiency measurement from the main charging location (my home) to somewhere else (work) and back. At least most of the time it would be more correct than it is now.

Re: Nissan Engineering Team Visit Dec. 3rd: Recap

Posted: Wed Dec 07, 2011 3:33 pm
by tbleakne
DannyAmes wrote:
TonyWilliams wrote: >>>>
Yes, the chief engineer did mention that they measure 96 voltages, and that the lowest / highest was part of the equation, as we know it has to be.
Here is a crack at the complexity of challenges the Nissan algorithm programmers have to rise to.
>>>>>>>>>>>>
Estimated Distance to Empty (DTE)
Energy consumption ratio could be more varible factor than SOC.
DTE would be better indicator - carefule drivers
DTE(km)=SOC(KWH) x Energy consumption rate (km/KWH)
Changed by Acceleration, Regen, Climae Ctrl, Gradient etc.

Danny
Here is my more simplified take-away from Kedota-san's last chart together with my own experience using the SOC meter.

I don't believe there is any disagreement that in the DTE equation above, most of the uncertainty in DTE derives from the Energy consumption rate factor, not the SOC. However, on this graph Kedota-san was illustrating that the SOC is not perfect.

The accuracy of the internally-generated SOC estimate (gids) is complicated by residual cell imbalance, temperature, rate of discharge, etc. Dispite this complexity, I feel the estimate presently generated is impressively accurate. At the very least it is stable. Yes, it does exhibit artifacts, such as sometimes going down at the beginning of regen, or up after the car sits off for a few minutes, but these artifacts are almost always +- 1 gid, which represents only about .3% of the total. I agree with a comment by Tony Williams that the SOC algorithm probably uses something like coloumb counting while discharging/charging recalibrated by OCV (open circuit voltage) when the battery has been idle for a short period.

The key point I saw on Kedota-san's graph was the importance both of cell-imbalance and temperature. There were no actual units on the graph, but it was clear how, for example only, a 1% variation of voltage over all 96 cell pairs would cause as much as 2% loss of battery capacity: 1% at the top of charge and 1% at the bottom.

I am seeing the temperature effect in the rate my Leaf charges. In warmer weather at the end of summer it was taking 4 minutes per 1% charge in the 80-90% range, and now it is taking only 3.5 minutes per 1% charge. Since I believe the power going into the battery is the same (I have not verified this), this implies a temporary reduction in pack capacity. It would be nice to get more precise data from others during this Winter.

I heard one suggestion during the discussion concerning the "predict the future" problem with the consumption factor: someone suggested that "crowd-sourcing" of Leaf Carwings data together with altitude profile data could yield better estimates of "consumption to destination." Perhaps a little unrealistic for now, but worth considering.

Re: Nissan Eng. Team Visit: Reservations Closed

Posted: Wed Dec 07, 2011 4:10 pm
by tbleakne
Boomer23 wrote:
KeiJidosha wrote:BTW, Your personal Chargepoint card will not operate on Google campus. Hopefully our hosts have a card with access.

Update;
One final footnote on the charging. I will make a sweep through all the L2 charger areas about 10 min before the meeting to make sure that all the chargers are activated. Howard, would you mind sending a last minute reminder to folks that have asked for charging to make sure they leave their charge port door open even if they can't activate the charger? I'll make sure they get plugged in. I don't want to have anyone stressing out because they can't get the charger to work.
KeiJidosha, doing his usual quiet, unsung helpful job. Did you drive the MiniE up there?
I was sure surprised when Matt was the first person I saw, efficiently directing traffic, as Tony and I pulled into the Google parking lot. He did the drive from home in 14 hours, stopping for charge 3 times. He used Tesla charging stations to get a fast charge. A whole different experience from our whimpy 3.3kW chargers and smaller battery, but as Mark Perry reminded me, at a different price point.

Re: Nissan Engineering Team Visit Dec. 3rd: Recap

Posted: Wed Dec 07, 2011 4:11 pm
by GRA
Wouldn't it be useful to tie something like Tony's chart into a GPS route, where you could enter the planned speed (for each leg, if different), average outside temp, desired inside temp, lights/defogger/audio use, desired range/charge reserve if applicable, etc.? Elevation change data should be already available to the GPS. Even if this can't be done with the current nav. system, I'm sure someone here has the knowhow to make a smartphone app.

Re: Nissan Engineering Team Visit Dec. 3rd: Recap

Posted: Wed Dec 07, 2011 4:16 pm
by TonyWilliams
GRA wrote: Even if this can't be done with the current nav. system, I'm sure someone here has the knowhow to make a smartphone app.
I've been working on the app for iPhone and Android.

Not sure when that might be ready. Another idea is a dedicated page on the current nav, but all these ideas take beaucoup time to develop. I'm having fun, though.

Re: Nissan Engineering Team Visit Dec. 3rd: Recap

Posted: Wed Dec 07, 2011 4:24 pm
by garygid
Assuming there is some reasonable "SOC" type value for remaining usable energy (RkWh):

And one cannot estimate a single, simple mi/kWh (edie) value and calculate a DTE that will satisfy everybody...

Providing a DTE-Setup screen that allows the user (who knows best what the future might bring) to select a mi/kWh "calculation-method" ... would come close to "good" for many situations:

Method 1. A fixed mi/kWh (edie) value is specified by the driver, for example as E = 4.8 (or some other value). Good for flatland, same drive, same weather, commuting type driving.

Method 2. The car creates the mi/kWh figure by averaging over the past S seconds, M minutes, H hours, D days, or N miles.

The LEAF probably uses something like N = 5 now (average over the last 5 miles).

With this very simple-to-implement "DTE-Setup" modification, the predictions of the calculated DTE could be made much more useful to many more people.

-------
I would use something like S = 10 for random driving to new places, meaning: If you keep driving like you are doing "now", this is APPROXIMATELY your expected remaining distance.

Thus, if I turn the lights or heater On (or Off), the DTE will adapt in 10 seconds.

Likewise, if it starts raining, or I get a sudden headwind, or I start climbing a hill, or speed up, or slow down, etc. ... I get useful (to me) 10-second feedback.

-------
Another DTE-Setup option could be to include P percent of the "reserve" (guess of energy remaining after the last fuel-bar goes away) in the DTE calculation. The default might be P = 0%.

In the New-Bar LEAFs, the "reserve" appears to be (usually) somewhere between about 10% and 15% of the total usable energy (but it can be less).

Re: Nissan Eng. Team Visit: Reservations Closed

Posted: Wed Dec 07, 2011 5:11 pm
by Phoenix
tbleakne wrote:
Boomer23 wrote:
KeiJidosha wrote:BTW, Your personal Chargepoint card will not operate on Google campus. Hopefully our hosts have a card with access.

Update;
One final footnote on the charging. I will make a sweep through all the L2 charger areas about 10 min before the meeting to make sure that all the chargers are activated. Howard, would you mind sending a last minute reminder to folks that have asked for charging to make sure they leave their charge port door open even if they can't activate the charger? I'll make sure they get plugged in. I don't want to have anyone stressing out because they can't get the charger to work.
KeiJidosha, doing his usual quiet, unsung helpful job. Did you drive the MiniE up there?
....snipped.
He used Tesla charging stations to get a fast charge. A whole different experience from our whimpy 3.3kW chargers and smaller battery, but as Mark Perry reminded me, at a different price point.
Understood re price point. But it would sure make it easier to help Nissan sell their current model LEAFs if we could point to all the QCs (in California) that could be used to extend the range. Otherwise, folks will keep sitting on the fence waiting for the 6.6 kw charger LEAFs to unveil.

Re: Nissan Engineering Team Visit Dec. 3rd: Recap

Posted: Wed Dec 07, 2011 6:24 pm
by walterbays
Herm wrote:
JohnOver wrote: How about a modification of that thought... When the car starts up it uses a long-term average (2 weeks?). It then uses the same algorithm that it uses now for the rest of the driving cycle.
Sounds simple enough, use a long term average for the first 10 minutes of driving when you start up the car.. best would be if we could switch among a few options.
I'd find it most useful if it would display a range of distance from the long term average to the short term average. Short term would give me expected distance if I keep driving as I am doing, and long term would give me probable distance.

E.g. if I were cruising on the freeway at 70, it might say: 58 - 77. If I were driving 25 on city streets it might say 77 - 93. With the existing dash displays it would be best if a configuration setting would let you choose between displaying only short term (as now), only long term, alternating between them, or average of short and long term.

Re: Nissan Engineering Team Visit Dec. 3rd: Recap

Posted: Wed Dec 07, 2011 7:17 pm
by davewill
walterbays wrote:I'd find it most useful if it would display a range of distance from the long term average to the short term average.
I'd be interested in having each of the mpk numbers in the history (or on the dash) have a DTE estimate next to it meaning that I can expect that range with the mpk value. Then I can reset them when appropriate, and exercise some control over the estimates. They can go ahead and keep the "smart" DTE in it's place.