Gid sensitivity to temperature

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chennu

Active member
Joined
Jun 13, 2011
Messages
33
Location
Portland; OR
I recently did a couple of 100% charges and came up with a gid count of 267. The ambient temperature in the garage is about 75-85 (depends on day). I was wondering if anyone did an analysis (or data logging) of GID count (or kwh accepted by battery) vs temperature.. in other words, am i out 7% or is the number going to get better as it gets cooler?
If already covered in another thread, then i can go search there.
 
chennu said:
I recently did a couple of 100% charges and came up with a gid count of 267. The ambient temperature in the garage is about 75-85 (depends on day). I was wondering if anyone did an analysis (or data logging) of GID count (or kwh accepted by battery) vs temperature.. in other words, am i out 7% or is the number going to get better as it gets cooler?
If already covered in another thread, then i can go search there.
Click to expand...

There are some scattered reports, but I don't think that the evidence is conclusive. As you are in Portland, OR, and it is like to be cooling down to 55 F overnight, why not park your Leaf outside overnight, or come up with a way to ventilate your garage to outside temperatures, and once you have a 5 temp bar condition, then repeat the 100% charge and report back to the board?
Edit:Fixed typo
 
WetEV said:
chennu said:
I recently did a couple of 100% charges and came up with a gid count of 267. The ambient temperature in the garage is about 75-85 (depends on day). I was wondering if anyone did an analysis (or data logging) of GID count (or kwh accepted by battery) vs temperature.. in other words, am i out 7% or is the number going to get better as it gets cooler?
If already covered in another thread, then i can go search there.
Click to expand...

There are some scattered reports, but I don't think that the evidence is conclusive. As you are in Portland, OR, and it is like to be cooling down to 55 F overnight, why not park your Leaf outside overnight, or come up with a way to ventelate your garage to outside temperatures, and once you have a 5 temp bar condition, then repeat the 100% charge and report back to the board?
Click to expand...

ok. will do tonite
 
chennu said:
I recently did a couple of 100% charges and came up with a gid count of 267. The ambient temperature in the garage is about 75-85 (depends on day). I was wondering if anyone did an analysis (or data logging) of GID count (or kwh accepted by battery) vs temperature.. in other words, am i out 7% or is the number going to get better as it gets cooler?
If already covered in another thread, then i can go search there.
Click to expand...

Well, you may have charge level reduced by the ambient temperature, or your gid count may be inaccurate, as an indication of kWh charge level.IMO if you use a gid meter, you should be trying to determine whether gids actually represent a constant wH value, since TickTock has recently posted his own observations that seem to indicate otherwise:


TickTock

My recent observation that my car came back with more gids on an 80% and 100% charge while still drawing the same power from the wall led me to go back and check more logs on the value of 1 gid. Using three turtle to 100% logs (so non linearity won't be considered a factor), I computed the total energy into the battery as the integral of V*I*delta_t and compared to the power from the wall for the same charge. Then I divided both by the number of gids that charge added:

11/21/2011:
input:
gid start: 6
gid stop: 256
wall start(kWh): 508.93
wall stop(kWh): 531.57
battery start(kWh): 0
battery stop(kWh): 20.02
computed:
charger efficiency: 88.4%
wh/gid into battery: 80.0
wh/gid from wall: 90.6

7/6/2012:
input:
gid start: 6
gid stop: 217
wall start(kWh): 2857.34
wall stop(kWh): 2878.11
battery start(kWh): 0
battery stop(kWh): 18.50
computed:
charger efficiency: 89.1%
wh/gid into battery: 87.7
wh/gid from wall: 98.4

8/11/2012:
input:
gid start: 5
gid stop: 232
wall start(kWh): 2979.18
wall stop(kWh): 3000.01
battery start(kWh): 0
battery stop(kWh): 18.82
computed:
charger efficiency: 90.4%
wh/gid into battery: 82.3
wh/gid from wall: 91.8

I think since the efficiency (power_into_battery/power_from_wall) is pretty consistent, the power_into_battery computation should be valid --> although 80Wh may be the nominal target for 1 gid, it can be off by as much as 10%. Just something to keep in mind if you are counting gids and cutting your range close. Maybe my car just got out of cal and they recalibrated it for me when it was in Casa Grand (between the 7/7 and 8/11 measurements), but I am going to be more cautious using a gid as an accurate unit moving forward.
Click to expand...

http://www.mynissanleaf.com/viewtopic.php?f=44&t=9689&hilit=+ticktock" onclick="window.open(this.href);return false;
 
Here's the plot TickTock did a while ago. Phil determined that a Gid was 80 Wh stored energy according to Nissan. We debated that at some length, but it's still unclear if the BMS is making some adjustments based on ambient temperature or other parameters.

While I would expect the total energy from the wall to be fairly consistent, this type of data might have limited accuracy and usefulness. Even if you assume constant charger losses, who knows where else this energy is going? It could be cooling fans, pumps, A/C, energy for cell balancing, etc. Can we be sure that all of these loads are going to be constant and nearly the same in any given charge event? And if not, how much of an error would this represent?


ticktockgidsgraphlarge
1
 
chennu said:
I recently did a couple of 100% charges and came up with a gid count of 267. The ambient temperature in the garage is about 75-85 (depends on day). I was wondering if anyone did an analysis (or data logging) of GID count (or kwh accepted by battery) vs temperature.. in other words, am i out 7% or is the number going to get better as it gets cooler?
Click to expand...
I can't speak to the intent of your question, but 267/281 = 95% so if Gids are an accurate source of information you have lost about 5% of battery capacity.
 
The days and nights have been substantially hotter here recently (August),
and my latest 100% charge achieved only 256 GIDs, a bit over 91% of new.

A primary factor seems to be aging, accelerated by heat.
A secondary effect appears to be just temperature, with permanence unknown.
 
chennu said:
I recently did a couple of 100% charges and came up with a gid count of 267. The ambient temperature in the garage is about 75-85 (depends on day). I was wondering if anyone did an analysis (or data logging) of GID count (or kwh accepted by battery) vs temperature.. in other words, am i out 7% or is the number going to get better as it gets cooler?
If already covered in another thread, then i can go search there.
Click to expand...


your car's numbers exactly match mine

http://www.mynissanleaf.com/blog.php?u=291&b=171" onclick="window.open(this.href);return false;

you need to average your GID count over a minimum of 3-4 measurements. i have had had up to 5 measurements not give me a full count so you need to keep measuring.

post your mileage, length of ownership, charging habits, etc. i started my experiment with a 2% degradation. so my experiment may have cost me 3% or its heat related and i will get it back. i should know more by the end of the week
 
Left the car out last night (first time in its 14 month life!) Just checked GIDs. ambient temperature was 52, car had 5 temp bars. 100% charge. GID = 263 (lower than the 266 i noted yesterday/charging inside the garage).

will keep trying 100% for a few more days to see if it rises, but so far I have not seen a number north of 266. so based on single data point, id say GID loss is not temperature dependent..
of course one data point is not enough data, but we'll see
 
chennu said:
Left the car out last night (first time in its 14 month life!) Just checked GIDs. ambient temperature was 52, car had 5 temp bars. 100% charge. GID = 263 (lower than the 266 i noted yesterday/charging inside the garage).

will keep trying 100% for a few more days to see if it rises, but so far I have not seen a number north of 266. so based on single data point, id say GID loss is not temperature dependent..
of course one data point is not enough data, but we'll see
Click to expand...

leave it outside for a week and tell us what happens. my GID count this morning

272. this is a full 60 hours after the warm weather left. my GID count was 263 3 days ago
 
edatoakrun said:
Any of you metering from the wall, to try to determine if the gid level fluctuations (as reduced by charge efficiency) are accurately reflecting kWh charge level?
Click to expand...

without a temperature based guideline and lack of a high resolution meter from the wall, i cannot. i have an analog power meter based on whole Kwh. great for lifetime averages but not so much for single charge events.

i can say for certain, in hot weather situations, a full charge is not always a "full" charge
 
Chennu; what is your mileage? what is your daily driving patterns? what is your normal charging habits? have you ever seen 7 TBs or more? how often do you QC and to what SOC?
 
DaveinOlyWA said:
Chennu; what is your mileage? what is your daily driving patterns? what is your normal charging habits? have you ever seen 7 TBs or more? how often do you QC and to what SOC?
Click to expand...

my milage = 9850
My wife drives the car to work and back. 11 miles each way. about 15-20 miles of errand running.
i have seen 7 TB once last year (hot day AC on, highway trip of about 37 miles).
i have tried QC once (to test if it works) for about 30 sec.
In winter charge to 100%(heater sucks power and dont want better half to worry).
in summer charge to 80%
mostly charge 110V (nose in parking). occasionally use blink
 
Gonna have to think that you might have spent too much time at a high SOC?

our situations are different in that I got double your mileage but mine has spent most of its life with SOC under 60%
 
could be.. let me see if a few more days of keeping in cool weather helps the GID.. its a hassle having to obsess about this in summer and winter
 
chennu said:
could be.. let me see if a few more days of keeping in cool weather helps the GID.. its a hassle having to obsess about this in summer and winter
Click to expand...

this morning it was pretty cool in the upper 50's and GID count was 274. now its taken a good 4 days to recover from the heat we had last week. but GID count has slowly risen from 263.

before the heat wave, i was at 275-276
 
DaveinOlyWA said:
chennu said:
could be.. let me see if a few more days of keeping in cool weather helps the GID.. its a hassle having to obsess about this in summer and winter
Click to expand...

this morning it was pretty cool in the upper 50's and GID count was 274. now its taken a good 4 days to recover from the heat we had last week. but GID count has slowly risen from 263.

before the heat wave, i was at 275-276
Click to expand...

same weather here in Oregon. Now my GID count is at 269.. slowly climbing up... will try one more time today before i chicken back to 80% charging.
 

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