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How you may be able to increase your CAC value

Discussion in 'Roadster' started by Perrin21, Jul 11, 2014.

  1. Perrin21

    Perrin21 Member

    May 18, 2014
    OK so i am already aware that CAC can fluctuate during the summer months but i would like to document and allow others to try and see if the following can help increase their battery health on their cars. I have seen a steady increase in my CAC over the past month since i got my car from circa 154.11 to 154.78 today resulting in a little extra range. The most recent significant increase followed a 150 mile drive i did on A and B roads from preston to leeds and back via Kendal and the south lakes. I drove very gently on the car and arrived back home with 154 estimated miles 140 ideal miles. The drive was on a lovely summers day (yesterday to be exact lol) and don't in max range mode following a full range charge with 1 hours for the battery to settle before setting out on the drive. Essentially a long range eco drive on a hot day has resulted in my battery charge CAC increasing by a small but significant amount. The car has today been charged in standard mode to 191 ideal and 199 estimated miles shown via my OVMS. I would like to see if anyone else can replicate the same situation and get a similar result with their own vehicle.

    1) Measure your current CAC on OVMS APP.
    2) Charge up fully in range mode
    3) Leave car for 1 hour to settle after its charged
    4) drive for 150 miles approximately using as much regen as you can on an eco route avoiding motorways. try and get home with over your ideal miles showing on the display by 10-15 miles e.g. 154 estimated 140 ideal and over 50% charge remaining.
    5) Charge up in standard mode on 3 pin 240v 13A until full.
    6) Measure your CAC on OVMS, has it increased or decreased?

    Lets see what happens over time with your results. Please post below and see if a pattern emerges.

    Mine was before 154.32 and following was 154.78.
  2. Mark77a

    Mark77a Member

    Jul 7, 2012
    Poole, Dorset, UK
    #2 Mark77a, Jul 11, 2014
    Last edited: Jul 11, 2014
    Interesting - well documented and clear details like this are a real help - thanks for posting.
    I've found similar small CAC improvements on a recent 225 motorway trip. But I didn't pay as much attention, and I did add about 1.5 hours worth of 'Dales Juice' aka 60 Amps on an ecotricity motorway rapid charger, cruising mostly at 70mph.

    you'll like the discussion in THIS thread too > CAC increased, ideal miles decreased

    If you are into this download your car's log file ... (you may have already done this ..but here goes anyway)..

    Download the Log file by putting in a 2Gb USB stick into the usb port as explained below by fellow roadster owners here on TMC ....

    You can safely download a PC program TeslaGLoP from TeslaFlux (I have it installed - no probs) ....... for info: HERE is forum discussion on how it was created and can be used).

    Basically you need the red tesla memory stick that came with the car OR a usb memory stick of 2Gb (to 8Gb) , wipe / re-format it in FAT ideally (or Fat32) and then add a new folder and name it: VehicleLogs

    Then with the ignition off .. plug it into car's USB socket (above 12v socket).
    The display should then say 'downloading log' (or similar) .. if not turn the key on and off and watch the screen tell you it is downloading the logs.
    It can take ages .. like 10mins or more so be patient.

    Then copy the folder to your PC, and open the file in it with TeslaGLoP.
    The data includes 2 logs a) lifetime log of major evens and b) rolling recent log of journeys/charges
    It includes all the useful stuff about the battery condition like CAC values, sheet and brick balance, lowest bricks etc.... like this...

    it also show max speeds, temps and SOC values.

    Now a question for all other Roadster owners: at 70 mph motorway speed in UK ambient eg 16 to 24 deg c what are normal motor temps ?
    My VDU is showing c 100 deg C (212 deg F ... last blue bar) this seems a bit high .. but the rear fan cuts in OK, and spins freely when I turn it, when cold, by hand.
    I just checked my logs and the actual temp is about 1/2 this, 50 deg C ... mmm I wonder if OVMS and tweaking has upset the VDU by swapping deg F for Deg F ie ...maybe a reset to defaults is in order.
  3. Alexandersims

    Alexandersims Member

    Aug 12, 2012
    near Cambridge, UK
    Regarding motor temps I'd say 100 degC is fairly normal. Thats what I would say I get if cruising at 70mph. at around 135/140 the motor goes into its first 'overheat' mode and dials back power significantly (You can still cruise at 100+mph though). I have never pushed it to the real upper limit but I believe it is around 170 from speaking to a previous Tesla technician.

    - - - Updated - - -

    From what I have worked out myself, a range charge certainly helps to balance the pack and help it calculate the top end. With a fullish discharge to around 10 ideal miles, it helps understand the lower range of the pack. So I think both are needed if it has sat around for a while or just been driven on short trips and constantly topped off.

    I have never worked out either why but on a 10/13amp 240v charge, it always charges slightly higher than at 32amps and even more than at 70 amps... Did you charge initially at 32amps? this may also be a factor in why you saw an increase in ideal miles on standard charge...

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