The Anatomy of a Gid

[DaveinOlyWA]

i will see it skip a GID and other times i will see maybe 3 GIDs "consumed" in say .3 or .4 miles when normally a GID lasts on average around .3 miles.

one thing for sure; the GIDs do not dissipate in a very orderly fashion. When i first got the meter, i tracked how long GIDs lasted and found using the odometer with a .1 mile resolution did not work well as GIDs lasted anywhere from .1 to .5 miles. the data i collected was so scattered i discarded it. even data like cruise controlled driving on the freeway was not consistent.

I have noticed a few times when i would gain GIDs when restarting like the other day (posted here somewhere) I had just hit LBW @ 48 GID when taking Son to appointment. After appointment, came out, started up and was at 52 GID but was back down to LBW within a half mile or so. the only reason i noticed this was because of the LBW. otherwise i rarely think to check the GIDs before turning off car

 

[cwerdna]

I don't mean to go too off-topic, but Phil (and MANY other Bay Area Leafers) were at the meeting last year where Kadota-san + many other Nissan folks were at. I unfortunately was in the back corner and couldn't hear well when Kadota-san stepped away from the mic during his explanations (when the slide was up about the "mysterious moves", which I think also said "Nissan strictly confidential" on it ).

http://www.mynissanleaf.com/viewtopic.php?p=155842#p155842" onclick="window.open(this.href);return false; was one summary. From Phil's expressions at the time, it seemed like he was following along pretty well/perfectly and could paraphrase's the CVE's explanations.

Has anyone (Phil?) sort of summarized and filled in the gaps from the above/discussion in that thread? I can definitely confirm some of the details but missed some important points. To me, this relates to gids. I'd imagine Phil and other folks have learned a lot in 11 months.

Maybe there already is one that I don't know about or I'm just dense?

 

[edatoakrun]

i "think" in your situation, you might be seeing a colder pack in the older LEAF. is it possible that one sat in the garage for a significant amount of time longer than the other one did?

I do not believe the temperature difference was too high. Both cars were in the garage Friday afternoon after light city driving. The old one was charged at 80% by Friday evening, the new one at 100% by 3:30 AM on Saturday. I did the measurement at 3:30 am and at 7:30 am after 30 minute of preheating. The old one had no driving on Saturday and just 10 miles on Sunday. It was charged at 100% on Monday morning when I measured the GID. All this time the temperature in the garage was around 60F and it was colder outside.

Any way, I need a good test plan for next weekend. Any suggestions are welcome. I am thinking of charging both at 80%, but one will have to be on L1. Drive them both exactly the same route (about 40 miles) and record miles, miles/kWh, and come home and charge them one at the time (one Blink only) and see what the wall consumption will be to get them back to 80%. I checked the tires last week but I will check them again on Saturday morning. All this if my wife approves it.

As for Carwings, I have not looked at it for months. Looks like there is an updated Carwings, I will look into that. The old car was at the dealer in June and it had firmware upgrades.

I would suggest you consider doing the two range tests on two days with similar temperature conditions.

This would allow you to do all L2 charging for consistency, though that might not be so important if you only test from a "80%" charge.

If you record the travel time between stops or at landmarks, you should be able to closely replicate the kWh use from your first test, on your second, even while varying in your speed as required by road and traffic conditions.

As to the usefulness of Carwings, please go to this capacity test thread to look at my recent test reports and look at the Carwings screenshots.

Note that CW not only compiles reports of total kWh use, but by breaking out the regen numbers on the "Electric Rate Simulation", it allows you to confirm that driving efficiency (excepting friction braking) has been replicated in your individual tests.

http://www.mynissanleaf.com/viewtopic.php?f=31&t=9064&start=30" onclick="window.open(this.href);return false;

Another range test, with recharge times compared, to give another view of the possible error in my LEAF's kWh use reports.

On 9/8/12 I made another "100%" to VLBW range test, repeating the same route I drove on 8/18/12, with close to 6,000 ft each of ascent and descent, with very slight variations in the final miles prior to VLBW, and got these results:

107.4 miles to VLBW, and 109.4 miles in total by odometer.

As reported by CW, 106.8 total miles (~2.5% under report), at 6.4 m/kWh, using 16.7 kWh.

Below is a screenshot of my CW "Electric Rate Simulation" including this trip:...

As you can see, the results are quite similar to those I got on 8/18, for my "100%" capacity range test on this same route. Trips two and three on 8/18, BTW, correspond to the single trip two above.

8/18/12 capacity test results:

107.1 miles to VLBW, 108.0 miles in total, by the odometer.

CW reports 105.4 miles (~2.5% under-report) total miles, at 6.2 m/kWh, 17.0 kWh used from 100% to about the same capacity level, slightly past VLBW.

Below is a screenshot of my CW "Electric Rate Simulation" including this trip on 8/18/12...

The slightly lower kWh use, 16.7 as compared to 17.0 in the earlier trip could be the result of a 5-10 F cooler battery while charging prior to the 9/8 trip, the greater Regen opportunity past the VLBW (received at ~100 ft. higher altitude) or it could be due to the dash, nav screen, and CW m/kWh "drifting" even further from accuracy, over the last few weeks.

I did not meter my charge a year ago, but I did record the charge time, and also got an accurate 16 amp 240v recharge time on 9/8/12. It took 4 hours and 16 minutes to reach 80% (and another one hour and 11 minutes to reach “100%”) following this trip.

Assuming a 3.75 kWh/h draw from my 16 a modified Panasonic charger, and the 16.7 total capacity from VLBW to 100% charge, I believe that this would indicate a charging efficiency from ~VLBW to the “80%” level of ~96%, which is implausible, in light of all reports of charging efficiency by others.

This compares to a recharge time of ~4 hours 25 minutes to reach “80%” following my first range test, on 9/7/11, with a reported 18.7 kWh used from 100% to about the same capacity level, ~VLBW.

This would seem to indicate a charging efficiency of from ~VLBW to 80%” a year ago of ~89%. but remember, this was recorded after my LEAF had seen most a of a Summer of use, so my LEAF’s m/kWh use reports might have already started to “drift,”meaning this percentage may already have been somewhat inflated, and the kWh use similarly understated...

So, I believe that the recharge time results are compatible with my range tests, which indicate no observed reduction in range, both probably indicating that my LEAF has no observable loss of available battery capacity (though some amount has almost certainly occurred) over the last 12 months.

I think it is also very likely that many other LEAFs have similar errors in kWh reports, quite possibly due to the gid Wh variability TickTock observed last year, and that capacity bar displays might be similarly effected. Not having lost a bar (yet) or ever having monitored my gid count, I can’t observe those results.

I do think that anyone seeing capacity bar losses or dropping gid counts should try both range and charge capacity tests, to try to more accurately determine their LEAF’s actual loss of battery capacity.

 

[TonyWilliams]

I have noticed a few times when i would gain GIDs when restarting like the other day (posted here somewhere) I had just hit LBW @ 48 GID when taking Son to appointment. After appointment, came out, started up and was at 52 GID

That should be the OCV adjustment. Normal.

 

[TickTock]

I noticed recently that when I remote start the CC before leaving, I have lower gids than if I don't (186 versus 194). What is fishy is I still show 394V on the battery. Since the battery voltage sensor should be accurate (doesn't have the same integrating errors from the Hall effect current sensor), I suspected that I was seeing an error in the gid reporting rather than a reduction in my available charge. So this morning I did an experiment where I topped off the battery, waited for it to complete, enabled logging and then remote-started climate control. After the car finished heating, I remote-stopped CC. I then parsed the log file, integrated the A*V going into the battery, and plotted the resulting kWh along with other relevant parameters. The graph below is the result. kWh uses the right hand scale, all the rest use the left. Note that pack volts remains 393-394 throughout and kWh *into* the battery ends up at ~+0.1 (just over 1 gid). So right there it looks like using the remote climate control option adds about (194+1-186)/(194+1)=5% error. Not enough time for temperature to play a role.

 

[stjohnh]

Just found this thread ..

Does anyone know or have any ideas why Gids on 2013 Leafs are so non-linear in the range between VLBW and Turtle. I find them completely unusable in that range.

The most reliable and useful range indicator for me is the SOC on LeafSpy, I find that (driving about 4.5 mi/kw) that remaining range is =SOC-3, over the whole range from 97% SOC down to 3% SOC (ie hits turtle=0 miles left) within 1 mile, impressively accurate.

 

[TickTock]

I think there has been some speculation on this early in the thread. It isn't unique to 2013. The area between 50 and 25 gids is near the knee in the voltage curve so possibly some errors in their formulas to adjust for pack voltage.

 

[DaveinOlyWA]

I noticed recently that when I remote start the CC before leaving, I have lower gids than if I don't (186 versus 194). What is fishy is I still show 394V on the battery. Since the battery voltage sensor should be accurate (doesn't have the same integrating errors from the Hall effect current sensor), I suspected that I was seeing an error in the gid reporting rather than a reduction in my available charge. So this morning I did an experiment where I topped off the battery, waited for it to complete, enabled logging and then remote-started climate control. After the car finished heating, I remote-stopped CC. I then parsed the log file, integrated the A*V going into the battery, and plotted the resulting kWh along with other relevant parameters. The graph below is the result. kWh uses the right hand scale, all the rest use the left. Note that pack volts remains 393-394 throughout and kWh *into* the battery ends up at ~+0.1 (just over 1 gid). So right there it looks like using the remote climate control option adds about (194+1-186)/(194+1)=5% error. Not enough time for temperature to play a role.

i noticed the same thing so i started checking my GIDs before i started the CC to see if I was losing anything despite running on "wall" power and the results were inconclusive. iow; sometimes i would lose some GIDs (4-8) and sometimes i wouldnt (losing one i consider to be nothing since I lose one fast frequently and by fast I mean by the time I back out of the garage and close it i then do my resets and record the daily data)

sometimes i wonder if my charging at 12 amps (still at 240 volts) is just not enough to keep up because the last 3 days (temps in the teens) I have been starting at 230-233 GIDs when last week without preheating was at 238-240

 

[garygid]

When pre-HEATING, the heater usually uses more energy than
comes from the wall, even though you are still plugged in.
So, there is a net drain on the battery pack.

The GIDs register that loss, and the pack voltage does also
but not enough to register if you are only looking at
whole volts.

For example, if each cell goes down two milli-volts,
the pack only drops 0.192 volts, which would drop 394.3
down to 394.1 (both would display as 394 volts when
truncated or rounded for display).

The GID-Meter attempts to show the Pack Voltage to
about 0.2 volts, by averaging. I think that the pack
voltage data from the car EV bus is only given to
about 0.5 volts, but I do not remember for sure.

 

[TickTock]

When pre-HEATING, the heater usually uses more energy than
comes from the wall

This is not what I observe. In the graph above, the heater *does* pull more power than the wall provides for about the first 500 seconds. After that, the power starts going back into the battery and at the end of the test, I ended up with 100Wh more power into the battery than when I started the climate control. I double-checked the sign on the current (negative is out of the battery in the graph) and you can also tell because the pack volts is sightly depressed in that first 500 seconds as the heater draws from the battery but then recovers back to 394V for the remainder of the test. What's more curious is even when the current reverses and starts flowing back into the battery, the gids are still decreasing. I can also confirm that the gids do not decrease any further if CC is left on for much longer (I've left it on for over an hour before and still ended up at 186 gids).

 

[Stanton]

This is all very interesting, but what's the take-away? Don't pre-heat for < 10 minutes (or so)?
I pre-heat occasionally in the winter, and with decreasing capacity I'm more sensitive to "dropping a few GIDs".

 

[TickTock]

This is all very interesting, but what's the take-away? Don't pre-heat for < 10 minutes (or so)?
I pre-heat occasionally in the winter, and with decreasing capacity I'm more sensitive to "dropping a few GIDs".

My take away is to not believe the lower gids reported when pre-heating while plugged in. At no time was the battery discharged more than a gid and, if anything, you end up with slightly more charge if left on more than 10 minutes or so.

 

[garygid]

Well, another EV mystery, it seems.
And, so much for my theory of how it should / might work.
Merry Christmas, Gary

 

[Berlino]

Does anyone know or have any ideas why Gids on 2013 Leafs are so non-linear in the range between VLBW and Turtle. I find them completely unusable in that range.

From LBW down to "---," I find that the percent remaining charge displayed on the MY13's dash is (Gid % - 0.5%) rounded down.

Since this figure dramatically understates remaining charge, I wonder if Nissan arranged for the inaccuracy, since they want people to stop before they turtle.

 

[surfingslovak]

Since this figure dramatically understates remaining charge, I wonder if Nissan arranged for the inaccuracy, since they want people to stop before they turtle.

That would certainly be plausible. When you look at the initial calibration of the GOM, right after the market launch of the LEAF, it followed a similar design philosophy. This became even more apparent after the battery gauge was remapped to the so-called "new bars" in the spring in 2011.

 

[bowthom]

Hello,
I routinely lose a bar of Battery when preheating w/240V. In this 25* weather the heater pulls more than the 3.3kW provided by the charger (typically 4.5kW). If I preheat less that 1/2 hour I will lose charge but at about 1 hour I break even or might gain some charge.

 

[TickTock]

Makes sense. Cooler weather may take longer for the heater to drop back down to 3.3 or less. In fact I wouldn't be surprised if, in some extreme cases, it never is able to keep up without battery help. I guess I should qualify my statement with "if the pack is reading 394V."
Bowthom, in your case, do you get the bar back after an hour (when the battery has been restored?)

Hello,
I routinely lose a bar of Battery when preheating w/240V. In this 25* weather the heater pulls more than the 3.3kW provided by the charger (typically 4.5kW). If I preheat less that 1/2 hour I will lose charge but at about 1 hour I break even or might gain some charge.

 

[stjohnh]

Since this figure dramatically understates remaining charge, I wonder if Nissan arranged for the inaccuracy, since they want people to stop before they turtle.

That would certainly be plausible. When you look at the initial calibration of the GOM, right after the market launch of the LEAF, it followed a similar design philosophy. This became even more apparent after the battery gauge was remapped to the so-called "new bars" in the spring in 2011.

That would fit also with the known increase in energy between VLBW and turtle that Nissan has programmed into the 2013 Leafs.

Does anyone know exactly what triggers turtle mode? It is clearly not Gids, nor SOC. Could it be a low voltage cutoff of the lowest voltage module? Since the primary function of turtle is to protect the battery, this would seem the simplest.

 

[garygid]

Since the LEAF does measure all 96 cell-pair Voltages, it is
assumed that the lowest cell-pair voltage is what stops the car,
and is probably what triggers Turtle mode.

 

[eclecticflower]

Makes sense. Cooler weather may take longer for the heater to drop back down to 3.3 or less. In fact I wouldn't be surprised if, in some extreme cases, it never is able to keep up without battery help. I guess I should qualify my statement with "if the pack is reading 394V."
Bowthom, in your case, do you get the bar back after an hour (when the battery has been restored?)

Hello,
I routinely lose a bar of Battery when preheating w/240V. In this 25* weather the heater pulls more than the 3.3kW provided by the charger (typically 4.5kW). If I preheat less that 1/2 hour I will lose charge but at about 1 hour I break even or might gain some charge.

I'm having a similar problem intermittently. It's been rather perplexing that I've lost a fuel bar before I've unplugged & exited my garage, after the car has pre-heated on-timer each morning. I expected the pre-heating process to always pull from the wall when plugged in. It seems to be pulling energy from the battery...are you saying this this normal, TickTock? Temps have been negative in MO lately, but it's always at least 35-45 in my garage, according to my dash readout. I was thinking I should take it to the dealer to troubleshoot, but don't want to waste my time there...