User avatar
aqn
Gold Member
Posts: 819
Joined: Fri Oct 01, 2010 12:59 pm
Delivery Date: 30 Apr 2011
Leaf Number: 1333
Location: Austin, TX

How accurate are the "energy economy" figures?

Fri Jun 24, 2011 9:42 pm

How does the LEAF measure power usage? Would it be anything like how my utility meter knows how much electricity I use? How accurate is the power usage measurement?

What I actually would like to know is, how accurate are the "energy economy" figures? If the display says "3.8 mi/kWh", have I really averaged 3.8 miles per kWh drawn out of the battery since the last reset? And if not, what do you think is the margin of error?

Thanks.
Anna Nguyen

rainnw
Posts: 283
Joined: Tue Aug 31, 2010 10:26 am
Delivery Date: 26 Jun 2015
Location: Seattle

Re: How accurate are the "energy economy" figures?

Sat Jun 25, 2011 12:51 am

The car is pretty accurate, however, I have noticed that on occasion it "freezes". For example, it completely missed the fact that i was accelerating from a stop and beginning to level off before it went from its max reading down to nearly zero. While its not much energy, the car missing some of the largest consuming moments of energy makes me wonder.

Many places where energy is being read though:

Your power company bill
Your power meter
EVSE
Car
CARWINGS (although inaccurate)
Ordered 11/24/2010 (November)
Delivered: 5/28/2011
Red SL-e, ECO package, cargo, splashguards
Commute: 75 miles round trip (60 miles highway, 15 side roads)
miles: 45,000 miles
Charge daily to 100%, lost 1st bar at 43k

http://www.chargesticker.com/

User avatar
garygid
Gold Member
Posts: 12460
Joined: Wed Apr 21, 2010 8:10 am
Delivery Date: 29 Mar 2011
Leaf Number: 000855
Location: Laguna Hills, Orange Co, CA

Re: How accurate are the "energy economy" figures?

Sat Jun 25, 2011 2:37 am

The "instant" mi/kWh "freezes" at 8 until your recently-Regen'd energy is used up. It is a design "feature".
See SOC/GID-Meter and CAN-Do Info
2010 Prius, now for sale
2011 LEAF, sold in 2015
2018 Tesla Model 3
2014 Tesla S, Model 3 in 2019
PU: SDG&E
Solar PV: 33 x 225W -> 7 kW max AC
To Sell: X-treme 5000Li EV motorcycle

DaveinOlyWA
Posts: 13868
Joined: Sat Apr 24, 2010 7:43 pm
Delivery Date: 16 Feb 2018
Leaf Number: 314199
Location: Olympia, WA
Contact: Website

Re: How accurate are the "energy economy" figures?

Sat Jun 25, 2011 8:10 am

ok... "my" Leaf does not have an "instant" energy usage gauge. mine has about a 2-3 second delay. i attribute this the gauge update cycle is i consider to be relatively slow. i only have my Prius to compare with which "seems" to give near instant feedback on energy consumption with gauge updates in the one second range.
2011 SL; 44,598 miles. 2013 S; 44,840 miles.2016 S30 deceased. 29,413 miles. 2018 S40; 15,000 miles, 478 GIDs, 37.0 kwh 109.81 Ahr , SOH 94.61, Hx 120.15
My Blog; http://daveinolywa.blogspot.com" onclick="window.open(this.href);return false;

User avatar
aqn
Gold Member
Posts: 819
Joined: Fri Oct 01, 2010 12:59 pm
Delivery Date: 30 Apr 2011
Leaf Number: 1333
Location: Austin, TX

Re: How accurate are the "energy economy" figures?

Sat Jun 25, 2011 1:52 pm

OK, that's the "instant" energy consumption readings. How about the "energy economy" readings e.g. "3.8 mi/kWh"? Any opinions as to how accurate those are?

(I've been recording all the pertinent numbers in a spreadsheet, and the "kWh per state-of-charge bar" figure is surprising, at least to me. I derive the "kWh per state-of-charge bar" from the energy economy figures, tripmeter reading, and number of SOC bars, so I just want to find out more about the accuracy of the "energy economy" figures.)
Anna Nguyen

DaveinOlyWA
Posts: 13868
Joined: Sat Apr 24, 2010 7:43 pm
Delivery Date: 16 Feb 2018
Leaf Number: 314199
Location: Olympia, WA
Contact: Website

Re: How accurate are the "energy economy" figures?

Sat Jun 25, 2011 3:40 pm

aqn wrote:OK, that's the "instant" energy consumption readings. How about the "energy economy" readings e.g. "3.8 mi/kWh"? Any opinions as to how accurate those are?

(I've been recording all the pertinent numbers in a spreadsheet, and the "kWh per state-of-charge bar" figure is surprising, at least to me. I derive the "kWh per state-of-charge bar" from the energy economy figures, tripmeter reading, and number of SOC bars, so I just want to find out more about the accuracy of the "energy economy" figures.)



well, that is a good question. i reset the energy screen every day and the gauge on the dash once a month. they do not agree with each other. the one on the dash consistently reads .1=.2 kwh lower so not sure how that is happening.

unfortunately, its the only thing we have to judge the amount of charge we have used. Carwings is simply wrong
2011 SL; 44,598 miles. 2013 S; 44,840 miles.2016 S30 deceased. 29,413 miles. 2018 S40; 15,000 miles, 478 GIDs, 37.0 kwh 109.81 Ahr , SOH 94.61, Hx 120.15
My Blog; http://daveinolywa.blogspot.com" onclick="window.open(this.href);return false;

User avatar
aqn
Gold Member
Posts: 819
Joined: Fri Oct 01, 2010 12:59 pm
Delivery Date: 30 Apr 2011
Leaf Number: 1333
Location: Austin, TX

Re: How accurate are the "energy economy" figures?

Sat Jun 25, 2011 8:33 pm

aqn wrote:OK, that's the "instant" energy consumption readings. How about the "energy economy" readings e.g. "3.8 mi/kWh"? Any opinions as to how accurate those are?
DaveinOlyWA wrote:well, that is a good question. i reset the energy screen every day and the gauge on the dash once a month. they do not agree with each other. the one on the dash consistently reads .1=.2 kwh lower so not sure how that is happening.
So far, the LCD panel's energy economy figure averages 97.8% of the center panel's.
Anna Nguyen

User avatar
planet4ever
Posts: 4674
Joined: Sat Apr 03, 2010 9:53 pm
Delivery Date: 02 May 2011
Leaf Number: 1537
Location: Morgan Hill, CA, south of San Jose

Re: How accurate are the "energy economy" figures?

Sat Jun 25, 2011 9:24 pm

I am coming to the conclusion that everything -- except the three odometers -- is subject to random voltage variations, or other non-linear analog measurements. I've driven the car pretty hard today, starting with a 100% charge and traveling 87.1 miles, mostly freeway, more than a third of it at 65-70 mph, almost all of it with A/C on. That's not too shabby, and I must say I am pleasantly surprised. Oh, my energy economy for the day? Only 4.0.

But, here's the reason for this post. I was 15 miles from home with one bar showing when I got the "low battery" warning. 'Oh, oh', I thought, 'this is going to be a squeaker.' I decided to take the old highway home rather than the freeway. It has half a dozen traffic signals and speed limits of 45 or 50 most of the way. Since my wife was with me, and I was determined not to strand her, I held my speed to 40 and cut the A/C, leaving the fan on. Ten miles later I still, to my amazement, had one bar showing, so I sped up to 45. Guess what -- I pulled in and stopped at home and still had one bar showing, though the guessometer was flashing 4. Naturally, no "very low" warning.

Fifteen miles after the low battery warning without even losing bar 1?? When we normally think of that warning as coming in the middle, or near the end of bar 1? It seems to me the BMS or dash computer must have seen a momentary voltage drop from the battery, and panicked. It seems to me I dropped from two bars to one prematurely, and got that low battery warning sooner than I should have. So, good luck on calculating kWh/bar, Andy. You may have to tack "+/-0.5" on your answer.

Incidentally, I was within a mile of South County Nissan in Gilroy when I got the warning, and I could have panicked too, insisting we stop there to juice up for at least half an hour. I'm glad I didn't; my wife would have hated it, and it obviously wasn't needed.

Ray
End of April 2013: Traded my 2011 SL for a 2013 S with charge pkg.

User avatar
ttweed
Posts: 1089
Joined: Tue Sep 07, 2010 8:31 am
Delivery Date: 01 Apr 2011
Leaf Number: 1317
Location: La Jolla, CA
Contact: Website

Re: How accurate are the "energy economy" figures?

Sun Jun 26, 2011 6:54 am

aqn wrote:How does the LEAF measure power usage? Would it be anything like how my utility meter knows how much electricity I use? How accurate is the power usage measurement?
I have to say there is a large difference between what you pull out of the battery and what you pull out of the wall. The numbers reported by Carwings for electricity usage are far lower than those reported by my utility. Last month we went 1216 miles on 336 kWh of energy usage, as billed by SDG&E on our separate EVSE meter (doing all our charging at home). That comes out to 3.619 m/kWh drawn from the wall. During the same period, Carwings says I am averaging 6.3 m/kWh. We do almost all our driving in Eco mode after charging to 80%, so it must be regen and charging losses that account for the difference? Or an optimistic Carwings calculation...

TT
Tom Tweed
La Jolla, CA
Plowshare Media
2011 SLe #1317 del. 4/1/11
1st bar lost at 31,953 miles
2nd bar lost at 38,685 miles
3rd bar lost at 50,711 miles
4th bar lost at 59,758 miles after 64 months
Battery replaced at 61,307 miles.

User avatar
evnow
Moderator
Posts: 11474
Joined: Thu Apr 22, 2010 11:41 am
Delivery Date: 25 Feb 2011
Leaf Number: 303
Location: Seattle, WA

Re: How accurate are the "energy economy" figures?

Sun Jun 26, 2011 7:58 am

aqn wrote:So far, the LCD panel's energy economy figure averages 97.8% of the center panel's.

That is because the center panel uses carwing's (GPS?) miles driven rather than the odometer. Carwings is consistantly lower by a few % - thus the m/kwh is higher by a few %.
1st Leaf : 2/28/2011 to 5/6/2013
2nd Leaf : 5/4/2013 to 3/21/2017
Volt : 3/25/2017 to 5/25/2018
Model 3 : 5/10/2018 to ?

Return to “Engineering”