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An ex-insider told me that minimal changes were made to the firmware when the R80 battery was developed. That suggests to me that Mark's assumption is correct.I too suspect an algorithm error. We know they don't have people working on the roadster firmware any more, and that algorithm must have been tuned for the behaviour of the old cells.
So then the question is, how does the range prediction progress over the course of the drive? I think we know that the number of ideal miles displayed at full is ratio of calculated Ah capacity to the original design Ah capacity times the original design ideal miles (340). Is the ideal range displayed during a drive simply based on starting with the number of ideal miles displayed after a range mode charge and then reducing that number according to the measured Ah discharge during the drive? If so, the prediction could be substantially wrong (in either direction) near the bottom. What triggers the display to switch to "cannot calculate range"? Could OVMS give us a better idea of how much range we have left by reporting the lowest brick voltage?The actual range you can drive concerns the 'bottom' of the pack, and is much simpler. When the lowest brick hits the low voltage limit, you're done.
I have a meter on the wall and find that the kWh number displayed on the VDS when first turning on the car after a charge is within 1 of the measured value. Calculating the charging losses accurately is tricky, though.But, yes, the way to know for sure is to do a drive from 100% down to 0%, measuring the actual kWh used (or charge the car back up measuring at the wall, while taking into account charging losses).
Doing a bunch of range charges won't work for me because I don't drive enough. However, I do have an upcoming long trip where I can do four range charges over five days.In addition to the experiment of running a battery all the way from full to empty and seeing how much charge (or Ah) it actually produces compared to the CAC, another thing to try would be to take a car that hasn't had all that many range charges and do a bunch in a row. If it's really doing measurements plus averaging (and if it's really consistently been underestimating the top), then the overall increase should be much bigger than what you see charging my car, since I've been doing it regularly. Probably the best car in the dataset to try this with is #33, @slcasner , since it's had few range charges and a pretty linear dropoff. If it wound up climbing back up to 200-205 Ah (roughly where my car was at the same mileage after range charging), that would indicate that the estimates just keep getting worse with no data, and also that mileage is more important than age (which is the opposite of what the CAC algorithm is saying).
I agree that is scary, but again I ask what triggers the display to switch to "cannot calculate range"? I don't think it is just the point where standard mode would indicated zero miles because with the original battery there were one or two occasions where I was driving in standard mode and nearing zero so I switched to range mode. I don't recall every hitting the point where the car said it could not calculate the range. Could that message be displayed when the apparent remaining capacity (and therefore range) is greater than what the algorithm had been calculating, as well as when it might be less?Been there, or very close to it last year after getting my 3.0 pack fitted. Did a range charge, topped out about 329miles, drove to Manchester (UK) and back to Oxford, about 300 miles roundtrip, on the way back in range mode the car suddenly jumped from 45 miles remaining to can not calculate range, leaving me fundementally terrified that I was about to brick the pack. Got home with a heart in mouth moment, everything switched off to minimise power drain less headlights (it was night!) doing another ten miles or so, and got car on charge, did the will charge faster with a 120V message - and after 24 hrs all was normal. That sufficiently scared me that I now never use range mode except for a range charge which I then switch back to normal mode at the 100mile mark. My SC say they're looking at it, but what that means I have no idea. Summary, it's not fun. :-(
Do you mean that the VDS displayed 20 miles but then the car suddenly died? Or did the VDS say it couldn't calculate but you thought you had 20 miles left because you had only driven, say, 50 miles from the point at which the VDS said 70? Also, if you went 375 miles without hypermiling, that's significantly more than 340.Yes had the same experience and when I THOUGHT I had about 20 miles of range left the car died, no warning just died. It did charge just fine but it was a rather expensive experiment. But I also set a personal record of 375 miles on a charge and I was NOT hypermiling
I thought that 10% SOC is zero for standard mode, but again, I don't think the display is expected to change to "cannot calculate range" if you are in range mode at that point.I think it's supposed to display "cannot calculate range" at 10% SOC, or ~35 ideal miles. So getting it at 45 means it was only off by 10 miles, or about 3% of the battery capacity, which isn't all that bad. Still scary.
Would leaving the car on in the garage (door open) with the A/C and Heat on full-blast be equivalent?Doing a bunch of range charges won't work for me because I don't drive enough. However, I do have an upcoming long trip where I can do four range charges over five days.
From some analysis I had done earlier (see https://teslamotorsclub.com/tmc/threads/roadster-soc-mileage-mode-decoder.92322/), I believe this is correct. Something in the 10%-ish range, based on miles when you flip between Standard and Range mode. I think my analysis came in at 11%, but it's in that general area.I thought that 10% SOC is zero for standard mode
Yes, those two numbers match well. The trouble comes in when you look at the logs and try to square it against what goes into the battery... See: https://teslamotorsclub.com/tmc/posts/2169156/ Still trying to clean up the stain on the floor from all the loose electrons.I have a meter on the wall and find that the kWh number displayed on the VDS when first turning on the car after a charge is within 1 of the measured value. Calculating the charging losses accurately is tricky, though.
Initially the car's report of kWh was not correct. At the Model S unveiling party I complained about this to JB so he asked for some data, which I provided in a followup email. After that they fixed the firmware.Yes, those two numbers match well. The trouble comes in when you look at the logs and try to square it against what goes into the battery... See: https://teslamotorsclub.com/tmc/posts/2169156/ Still trying to clean up the stain on the floor from all the loose electrons.
I too suspect an algorithm error. We know they don't have people working on the roadster firmware any more, and that algorithm must have been tuned for the behaviour of the old cells.
David, how is your car battery performing.
Hey bolosky,
How often do you want updates on the CAC? Since I'm taking over #209 I want to continue to supply data to monitor these batteries.
I e-mailed you with my 0707 logs and a question. Check your spam folder.Every few months, maybe quarterly. Msjulie sent me an update right before so sold the car, so you've got a while.
And thanks!
I'm not sure how I could measure that from the data that I have.
I realized I mixed up the colors of 209 and 670. Looking at the latest data 670 does in fact show leveling out. Since the car with the most use is showing flattening capacity loss either it's the first one to hit that part of the curve or the use profile allows the algorithm to more accurately calculate actual capacity. Or a bit of both I suppose.Does 209 appear to be leveling out?
I realized I mixed up the colors of 209 and 670. Looking at the latest data 670 does in fact show leveling out. Since the car with the most use is showing flattening capacity loss either it's the first one to hit that part of the curve or the use profile allows the algorithm to more accurately calculate actual capacity. Or a bit of both I suppose.