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This is a highly interesting thread, thank you for keeping it alive and for sharing all this information. I wouldn't want to sidetrack the discussion, but I found a similar thread over on the Tesla forum. They use predicted ideal miles as a proxy for battery capacity and have a longer time frame to look back at. There is apparently a way to get calculated battery storage capacity as well. What's interesting is that the usual suspects surfaced there as well: ambient temps, cell balancing, 120 vs 240V charging, etc.

http://www.teslamotorsclub.com/showthread.php/6339-Ideal-range-gradually-dropping-off" onclick="window.open(this.href);return false;

I found the following two plots to be quite interesting (they are from two different cars):

attachment.php


charge_history.png
 
So, the battery goes up in capacity in the first 50 days, and then 530 days later, starts dropping off? Am I reading this correctly?

That would eliminate seasonal temperature variation from that model.
 
TonyWilliams said:
So, the battery goes up in capacity in the first 50 days, and then 530 days later, starts dropping off? Am I reading this correctly?
Click to expand...
Yes, that's my interpretation as well. I'm a bit surprised how the first car didn't see any battery degradation for about two years and the second car had significant range reduction, and has subsequently recovered. My takeaway from the Tesla thread is that owners are seeing fair bit of variance in predicted range, and although there is no clear consensus on contributing factors, cell equalization, ambient temps and charge voltage (120 vs 240) are the front runners. The average annual range loss seems to be around 4%, which is roughly in line with Tesla's official estimate (70% of original range after 5 years).
 
So much for my temperature theory....I charged to 100% from 38.5%, starting immediately after arriving in Santa Monica on Friday, and got 99.6% 280 units for my trouble. So you can take battery temperature and time related resting state out of the equation. I'm still not convinced that SOC remaining at the beginning of charging is a lost cause yet....38.5% is still quite a bit higher than under my normal circumstances.

I am, however, leaning harder on my theory that the battery cell balancing degrades until it reaches some tipping point, after which a balancing event is triggered, perhaps taking us back closer to optimum.
 
I just found this thread and spent the last 2 hours slogging through all the history. Very interested in the subject since I cannot seem to come even close to 281. 80% charge takes me to ~195 and 100% charge takes me to ~240. At least the ratio 100/80 is within error bars but the high value is disturbing to me. Particularly since I only get ~46 mile from 80% to LBW (no freeway). I am in PHX and up until mwalsh's last post was thinking temp could be my culprit (I start the charge at 6pm when the garage is still ~100F). However, last night I plugged in at 11pm (garage was considerably cooler) and still hit only 197 gids and 386V on an 80% charge.
 
TickTock said:
Very interested in the subject since I cannot seem to come even close to 281. 80% charge takes me to ~195 and 100% charge takes me to ~240. At least the ratio 100/80 is within error bars but the high value is disturbing to me. Particularly since I only get ~46 mile from 80% to LBW (no freeway).
Click to expand...
I would take the car to the dealer to have the battery checked--195 gids is awfully low for 80% charge.
 
Started charging at 11pm with 61 gids and 2 bars remaining
Ended 80% charge at 2am with 197 gids, 9 bars, 386V having drawn 11kWh from the wall
Started charging again at 10:20am with 197 and 9 bars
Ended 100% charge at 11:30am with 238 gids, 12 bars, 394V having drawn 4.3kWh from the wall

I guess I should mention my capacity guage still indicates 12 bars.
 
You humanoids crack me out! :lol:

TickTock,
Your charge results are certainly strange.
Your 11 PM to 2 AM is too short to finish charging, right?
Are you sure that you are finishing charging in the morning session?
Try no timers, and let it charge until it is complete.
What EVSE are you using.
Have you tried a different plug or charging location?

Is the CAN-Selector switch of the GID-Meter in the position to select the EV-CAN bus?
 
TickTock said:
Started charging at 11pm with 61 gids and 2 bars remaining
Ended 80% charge at 2am with 197 gids, 9 bars, 386V having drawn 11kWh from the wall
Started charging again at 10:20am with 197 and 9 bars
Ended 100% charge at 11:30am with 238 gids, 12 bars, 394V having drawn 4.3kWh from the wall
I guess I should mention my capacity guage still indicates 12 bars.
Click to expand...

For an 80% charge your raw was 197, but what was your SOC%? For a 100% charge your raw was 238 and your SOC was what %?
 
TonyWilliams said:
LEAFfan said:
For an 80% charge your raw was 197, but what was your SOC%? For a 100% charge your raw was 238 and your SOC was what %?
Click to expand...
The % is merely a factor of 238/281, or:
84.69% (his 100% charge)
197/281 is:
70.10% (his 80% charge)
Click to expand...

Oh, I know that, but I don't have 'raw' data yet, just the SOC% so now I understand that he definitely has a problem. When I charge to 80%, the SOC always shows close to 77% (10 bars). I only charge to 100% once a month to balance the pak, but I'm going to doubt it will read 100% SOC...prob high 90's.
 
99.2% / 279 Gids last night, charging from just above 50% discharged. So depth of discharge is still looking like a likely precursor to receiving a good result, because I've never had two good charges in a row like that before. But then I don't normally charge with more than ~30% of remaining charge.

What I'm going to try and do is keep a log for the next few weeks and see if a pattern emerges to support the other theory I have (cell balance degradation).
 
Thanks for all the fb. I am due to come in soon for the tire rotation so I'll tell them about my reduced range and try to get the full battery check even though it's been only 4 months.

mwalsh,
I've been using a spreadsheet on GoogleDocs to log mine - it is really nice since you can create a form for all the data you want to gather, then you can just enter into the form using your smartphone browser or the googleDocs app. It will timestamp it for you and you can even share with others if you want to gather inputs. Sorry if you were already aware of this, but I only recently discovered it and think it's pretty cool. I only wish I started gathering this data as soon as I received the car.

My log:https://docs.google.com/spreadsheet/ccc?key=0An7gtcYL2Oy0dHNwVmRkNkFnaEVOQTVENW5mOTZlb0E&hl=en_US
 
Another data point:
Started with 53% last night. Ambient temp in low 50s overnight while charging. 5600 miles on car since April. Ended up with 279 gids this morning (wife overrode charging timer, later apologized for not realizing this would give us 100% charge rather than 80%).
 
TickTock,
From the Spreadsheet, the voltages look reasonable, but the SOC values are strangely low.

Charging to 80% overnight last night, I got 82.2%, or 231 gids ... which is quite normal for the temperatures around here.

We do believe that higher temperatures can/do cause a lower SOC to be "calculated" by the car, but your SOC seems to be much lower than any others that have been reported.

The fact that your Bars and Battery Voltage are both high is encouraging, but it would seem to tell us that the Bars being shown are not strictly a function of the internal "soc" number that we use, ... or that there is another "SOC" nunber that is being used to make the "Bars".

Can you try to measure your car with another SOC-Meter, just to eliminate the Meter as a possible source of this error?
 
garygid said:
TickTock,
From the Spreadsheet, the voltages look reasonable, but the SOC values are strangely low.

Charging to 80% overnight last night, I got 82.2%, or 231 gids ... which is quite normal for the temperatures around here.

We do believe that higher temperatures can/do cause a lower SOC to be "calculated" by the car, but your SOC seems to be much lower than any others that have been reported.

The fact that your Bars and Battery Voltage are both high is encouraging, but it would seem to tell us that the Bars being shown are not strictly a function of the internal "soc" number that we use, ... or that there is another "SOC" nunber that is being used to make the "Bars".

Can you try to measure your car with another SOC-Meter, just to eliminate the Meter as a possible source of this error?
Click to expand...

Be happy to except I think you told me I was the first to buy one in Phoenix so there aren't too many nearby. However, since the battery voltage, current and power are all in line, I think it is unlikely something is wrong with the meter. I do have a couple of logs I captured for a few trips. I will try to capture a log during charging tonight. Maybe plotting the voltage or temp will shed some light...

I have always charged from home on my AV charger - the only exception is when it was charged at the dealer. I think I will try the trickle charger and see if that reaches a different charge state.
 

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