Tesla 940
Member
I'll complete the questionnaire in the next day or two. Regarding the CAC (what ever that is), unless the instructions are on the level of "CAC for Dummies" I'll be hopeless.
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A Tesla service tech can read the CAC value for you. If that's not practical, there are a couple of other methods for getting it. If you've already submitted a survey report, send me a private message. If you haven't submitted a report yet, go ahead and submit without the CAC value and put a note in the comments that you need info on getting the CAC and I'll contact you.
It occurs to me that I haven't explained why I care about CAC...
Tesla techs have been telling owners that the best measure of the car's battery capacity is the CAC value. I don't know what CAC stands for (I have some guesses), but it's a measure in amp-hours (Ah) that's probably something like the average Ah capacity of the bricks in the battery, or maybe a more complex measure of how much energy can be used from all of the bricks while also protecting the weakest and strongest bricks from getting over- or under-charged.
A nominal new pack starts about about 160, and then drops as it loses capacity with time and use. It's given as a decimal number with two digits after the decimal, like 123.45.
I'd like to see how well CAC correlates with Standard and Range mode ideal range after a full charge. I suspect CAC will be a very useful number for Roadster owners to know and understand as our packs age.
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I want the actual CAC, not one of the values that our parsers have identified.
The CAC can be read in a few seconds and does not require a full bleed test.
Tesla techs have been telling owners that the best measure of the car's battery capacity is the CAC value. I don't know what CAC stands for (I have some guesses), but it's a measure in amp-hours (Ah) that's probably something like the average Ah capacity of the bricks in the battery, or maybe a more complex measure of how much energy can be used from all of the bricks while also protecting the weakest and strongest bricks from getting over- or under-charged.
A nominal new pack starts about about 160, and then drops as it loses capacity with time and use. It's given as a decimal number with two digits after the decimal, like 123.45.
I'd like to see how well CAC correlates with Standard and Range mode ideal range after a full charge. I suspect CAC will be a very useful number for Roadster owners to know and understand as our packs age.
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I don't know if the techs can pull the CAC out of the logs. So far, we've identified numbers in the log file that are close to the CAC value (average and minimum brick Ah), but aren't quite the same. I've seen cars where the CAC value is near the average brick Ah number in the logs, and others where it's closer to the minimum, with significant differences between the two.
I want the actual CAC, not one of the values that our parsers have identified.
The CAC can be read in a few seconds and does not require a full bleed test.
Tesla 940
Member
TOMSAX,
I'm getting the information for the survey but I can't find the screen that gives the Assembled Date. I have a 2.0 or 2.25. Any more information would be helpful. I did buy the car new so an Assembled Date is pretty easy to estimate.
Thanks,
Don
I'm getting the information for the survey but I can't find the screen that gives the Assembled Date. I have a 2.0 or 2.25. Any more information would be helpful. I did buy the car new so an Assembled Date is pretty easy to estimate.
Thanks,
Don
strider
Active Member
With the vehicle off, touch the VDS screen to wake it up. Then touch the "i" button and then "Vehicle Info".
That's my favorite guess at the meaning. Have you heard from a reliable Tesla source that that's the official term?
Past the 100 vehicle mark!
We're past 100 vehicles on the survey! Thanks to everyone who has contributed and helped spread the word!
The survey data is already providing helpful information. I recently developed a charge time predictor algorithm and used data from the survey to help build the model. I expect this will be used to add functionality to both OVMS and the Tesla Tattler. In related news, Mark found the CAC value on the CAN bus, so we may soon have an easy way for OVMS and Tattler users to get the CAC value. I'm also taking another look at the log files to see if I can find it there.
It's going to be at least next week before I can start analyzing the survey data, so I'm still interested to get more/updated data into the survey. Please jump in!
Plug In America Tesla Roadster Survey
We're past 100 vehicles on the survey! Thanks to everyone who has contributed and helped spread the word!
The survey data is already providing helpful information. I recently developed a charge time predictor algorithm and used data from the survey to help build the model. I expect this will be used to add functionality to both OVMS and the Tesla Tattler. In related news, Mark found the CAC value on the CAN bus, so we may soon have an easy way for OVMS and Tattler users to get the CAC value. I'm also taking another look at the log files to see if I can find it there.
It's going to be at least next week before I can start analyzing the survey data, so I'm still interested to get more/updated data into the survey. Please jump in!
Plug In America Tesla Roadster Survey
smorgasbord
Active Member
@Smorgasbord
Can you add upper bound, lower bound, and average fit curves to that chart?
I think I'm seeing nearly linear upper, exponential/logarithmic lower, and something in between for the average.
Thanks.
Updated: See Roadster Owner Based Study of Battery Pack Capacity Over Time - Page 22.
Can you add upper bound, lower bound, and average fit curves to that chart?
I think I'm seeing nearly linear upper, exponential/logarithmic lower, and something in between for the average.
Thanks.
Updated: See Roadster Owner Based Study of Battery Pack Capacity Over Time - Page 22.
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Almost looks to me like there is a slope followed by a knee then a straight line. Curious!
Of course this might be an artifact of fewer data points on the RHS of the graph.
Of course this might be an artifact of fewer data points on the RHS of the graph.
There are now multiple ways for owners to find out their CAC value without going through a Tesla service tech.
Thanks to some awesome work by markwj, we can now read the CAC from the car's CAN bus. The latest release of OVMS supports showing the CAC value in the SMS response to a STATUS command.
The Tesla Tattler will be supporting CAC as well.
Thanks to Mark's work, I was able to track down a value in the log file that tells the car's CAC value, although it's less precise than what a service tech or OVMS can read from the car: ±0.03. This value is now available in VMSParser, my Mac/Win command-line based parser, as well as TeslaGLoP, Doug_G's graphical parser for Windows.
Either the precise CAC value from a Tesla tech or OVMS/Tattler, or the slightly less precise value from the one of the log file parsers is suitable for adding to your vehicle report for the survey. If you haven't already submitted your CAC, please either update your report or, if you haven't already participated, please submit a report.
Thanks to some awesome work by markwj, we can now read the CAC from the car's CAN bus. The latest release of OVMS supports showing the CAC value in the SMS response to a STATUS command.
The Tesla Tattler will be supporting CAC as well.
Thanks to Mark's work, I was able to track down a value in the log file that tells the car's CAC value, although it's less precise than what a service tech or OVMS can read from the car: ±0.03. This value is now available in VMSParser, my Mac/Win command-line based parser, as well as TeslaGLoP, Doug_G's graphical parser for Windows.
Either the precise CAC value from a Tesla tech or OVMS/Tattler, or the slightly less precise value from the one of the log file parsers is suitable for adding to your vehicle report for the survey. If you haven't already submitted your CAC, please either update your report or, if you haven't already participated, please submit a report.
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strider
Active Member
So I'm curious how this is different from the amp-hour numbers we get from the -b option? The parser reports my CAC as 151.97 and my brickahmin as 151.64.
Through a bunch of careful logging, I found that CAC corresponds perfectly with the value that Scott uses to calculate brick min amp-hours, but I had to use a slightly different scale factor than what Scott uses.
I don't know how Scott determined the scale factors for the brick min and max amp-hours, and now he can't tell us. I trust he had a reason for picking the scale factor he uses for those two values, but I can't explain why it's different.
dhrivnak
Active Member
Hey new owners. If you have not yet filled out the survey for battery life I urge you to do so. Plug In America Tom has done a wonderful job here and one is able to pull the summary data into Excel. It looks like one should have 150 ideal miles in standandard charge after 135,000 from what I can gleam from the data. Of course with more data we will have a far more accurate projection. So please add your data.
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