Efficiency on a fixed route varies?

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ebeighe

Well-known member
Joined
Jul 5, 2017
Messages
96
Location
Phoenix, AZ
I'm relatively new to Leaf, since July.
I live in Phoenix so temperatures are relatively high

I've made a particular trip about 2X per week and according to leafspy, the net power is usually a little less than 900W.
(it's slightly downhill; 7.5miles, all "in town" traffic which here means ~ 40mph arterial streets, for a remarkable 8.3 miles/KW)
However, sometimes the power is remarkably higher. Today it was 1200W; and nothing about the trip seemed any different than usual.
I get that if the battery is fully charged when i start, there will be less regen and therefore expectedly higher net power on a trip. Today the car was charging up until when i left, but was nowhere near fully charged (78% according to the car IIRC)
And also, differences in of regen (according to the leafsyp trip log) wouldn't explain the large differences.

Battery temperature today was 72F upon departure. Had i not been charging the temp would have been about 60F

Is there something about it being recently charging? Is the extra power really being used, or is it just some artifact?
 
Not really all that different than with an ICE, except for the obvious difference that a gas engine has an optimal operating temperature and it takes awhile for an ICE to reach that temp.

Factors that could explain day-to-day variability:

  • Ambient temperature vs cabin temperature gap - more energy needed as ambient drops
  • Tire slippage increases in rain or snow, as well as more energy needed for wiper motors, etc
  • Drivetrain fluids are more viscous, causing more friction, at lower temps
  • Higher humidity: more energy needed to heat cabin
  • Ambient temperature: the colder the air, the more dense it is, the more aero drag increases
  • And lots of other factors...
 
Another factor: other traffic. E.g., a slow car in front of you causing you to slow down and speed up again will increase your usage.
 
Let me be clear -- this topic is for energy nerds :roll: :D
thanks for the ideas; a couple things i should have mentioned:

  • I don't use ANY heat or a/c on that trip, sometimes i turn on the fan a little; I pretty much keep the windows up (yes, energy nerd; wanted to keep it consistent; even though at these moderate speeds i doubt it makes much difference)

    I make the trip first thing in the morning, on weekdays only. Traffic is quite consistent; and doesn't seem to be much of a factor (i would hypothesize 'bad" traffic would show up as higher net and higher regen)

    I don't recall it every raining on that trip (phoenix. it doesn't rain much here, and while we do get violent storms they would tend to be not at this time of day). It doesn't ever snow here.

    Likewise wind: it's rarely windy here, and the air tends to be still at that time of the morning (typically the time is around sunrise). I do the same trip the other 5 days a week by bicycle, i do really notice wind when there is any.

    Ambient temps: remember I've been doing it beginning in July thru now -- more or less hottest to coldest ambients; in round numbers from 90F -> 50F. I would expect if it were true ambient is significant I should see a trend

    I haven't been consistent with headlights, however IIRC the non-led headlights are something like 150W; the trip is like 15 to 20 minutes, so headlight use would be +/- 50W

-----

Nobody suggested this but let me bring it up: perhaps it's just an artifact of the way the battery management system reports or thinks, rather than actually being consumed.?
Might it matter if the energy is coming from the "top" of the pack vs. the bottom (a higher SOC vs. lower) (besides the obvious: if battery is full it won't regen)?
Charging?

I need to collect more data but it takes awhile because car isn't used much; plus sometimes i forget the gadget i run leafspy on :)
 
I drive the same route every work day, 50 miles round trip. Car always starts at 100% charge. My OCD is taking note of the dash SOC% at certain checkpoints in my commute, every day. I don't suffer from range anxiety as I know I have enough capacity to make my trip (and AAA roadside service if things went sideways). I find that there are far too many variables outside of my control for a consistent experience. At 1/3 of my commute my SOC can land in a 3% wide band. By the time I get to work, it can vary about 6%. When I pull into the driveway at home, that range can vary by 10% (and that's without rain or high winds).

I park in the garage, so temps are about as consistent as I can get them. Regardless of my best efforts, that 1/3 mark can land on anyone's guess. Some days I think I'm doing great with my efficiency, but get there with less SOC than expected, and some days are the complete opposite. Not sure how consistent the BMS end the battery every day after charging, so that starting charge is probably a factor too. Also, I deal with a lot of grades from 6% to an 8%, with varying levels of traffic present.

All in all, my usage doesn't vary much when you factor in all those variables. I've come to the conclusion that I will just try to not drive aggressively and I seem to stay within the usable range of the vehicle with a 25% SOC buffer to turtle on the lowest end.
 
ebeighe said:
...Nobody suggested this but let me bring it up: perhaps it's just an artifact of the way the battery management system reports or thinks, rather than actually being consumed.?
Might it matter if the energy is coming from the "top" of the pack vs. the bottom...
Very much so.

Even if you control all variables perfectly, and use exactly the same amount of energy, you should not expect the LBC to report the same energy use, particularly when you use a different part of the pack's charge range.

Unfortunately, since you have an S, you don't have the ability to use a range/capacity test to accurately measure energy use and capacity, and can only see these factors as very inaccurately reported by your LBC.

I can tell you that in my 2011, Wh per gid, as measures in range/capacity tests, varies from ~40 near the top of the pack (starting from "80%" charge with full regen) under descent conditions, to over 140 Wh/Gid between the LBC and VLBC.

edatoakrun said:
100 Mile Club, 200 km, 300 km, 200 Mile Club (24kWh LEAF)

I was only able to complete eight range/capacity tests in the last year on my usual mountainous route from my home to Burney Falls State Park and back, using the charge allowed from "100%" to ~VLBW, since my last post on the previous page.

I completed two trips over 100 miles, bringing my LEAFs total of trips over 100 mile-on-a-charge to thirty-two since delivery.

It has quite clear for many years now that my LBC is significantly pessimistic in over-reporting capacity loss, and apparently by a similar percentage that it has been under-reporting kWh use.

So, I estimated the actual kWh use anjd m/kWh in all the entries below by multiplying the kWh use from the dash/navscreen, and the Carwings kWh use reports by 1.11, which is the ~the average under-report of kWh use over the year, calculated by using an external meter to measure the kWh my pack accepts from the grid...

I also made two 100+ mile runs on trips back from the Bay area last summer, both with small net ascents.

The first was on 7/29/15, 101.9 m (~102.1 actual) from Winters to Corning, ending with 31 gids reported by the LBC.

The second was on 9/8/15 from Vacaville to Corning, ~14.7 kWh,112.6 m (~112.8 m actual) to VLBW, 14.8 kWh 114.2/114 .4 total miles to destination.

The most interesting aspect of this trip was that I drove 25.8 m from LBW to VLBW, meaning the LBC let me use ~3.3 kWh nominal (~3.6 kWh actual) between the two warnings, and so the average Wh/gid was ~132 nominal (~144 actual) during that segment, the highest I've ever seen...
 
DuncanCunningham said:
tire pressures? do you have a tire going flat?
Ah, good point -- should have mentioned i'm pretty cognizant of tire pressure; i keep it around 39 and it's right on the page of leafspy so i do get reminded of it.
 
edatoakrun said:
Unfortunately, since you have an S, you don't have the ability to use a range/capacity test to accurately measure energy use and capacity, and can only see these factors as very inaccurately reported by your LBC.

Hey that's interesting. Question: what makes a non-S (an SL or SV) more accurate? I was under the impression that leafspy gets the same data(?)
 
ebeighe said:
DuncanCunningham said:
tire pressures? do you have a tire going flat?
Ah, good point -- should have mentioned i'm pretty cognizant of tire pressure; i keep it around 39 and it's right on the page of leafspy so i do
get reminded of it.
Sorry I missed that post where you menation about the LeafSpy part.. essential for any leafy geekoo
 
powersurge said:
Nissan should rip out all the gauges except the battery%.

Then people would just drive the car and not become obsessive compulsives...

I'm still new to all this, but I hate that battery% gauge the most. It's maddeningly non-linear. Sometimes I'll drop 4% in a mile of careful driving. WTF? I'm def getting OCD about that, I'm happiest in the short times when I look at the other gauges. I know the GOM is pretty inaccurate, but its coarse granularity is a blessing compared to those fine little percentage units.
 
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