TMC is an independent, primarily volunteer organization that relies on ad revenue to cover its operating costs. Please consider whitelisting TMC on your ad blocker or making a Paypal contribution here: paypal.me/SupportTMC

Falling CAC on public chargers UK

Discussion in 'Roadster: Technical' started by Perrin21, Aug 11, 2014.

  1. Perrin21

    Perrin21 Member

    Joined:
    May 18, 2014
    Messages:
    63
    Location:
    uk
    OK this post is not conclusive and is only an insight into my current situation and to see if others have experienced the same. My car has regularly been charged by its previous owner on the Tesla HPC only and the CAC value after 15000 miles was 154.11. I ordered a CAN from HC Sharp and a J1772 to Mennekes cable (32A) from Ebay and began using the Ecotricity 60A electric highway @ 60A as others have. I imediately (within days noticed my CAC fall to 152 and recently its now fallen to 150.11 its all time lowest figure. The initial fall happened within 1 charge (100 miles from 154 to 152). Firstly i do not believe this has anything to do with the excellent HC sharp CAN adaptor. I do however wonder if it has anything to do with using either the Ecotricity charger (which so far has appeared also to be faultless and charged at 60A without issue) or the use of the 32A cable (most likely). Has anyone else noticed this strange phenomenon?. Last night after a weekend away in Milton Keynes (charged mostly on ecotricity with my latest CAC of 150.29) i decided to run the car via Stafford to use the Tesla 70A HPC and arrived with only 21% charge on the car. At the end of the standard charge, ended early as i had my partner with me who was getting restless, the CAC had risen to 150.89. I could be on to something or nothing at all but i wanted to mark my findings here to see if anyone else had noticed a fall on the 32A cables and ecotricity vs an increase in CAC value on a HPC charger? It certainly has motivated me to get my Tesla HPC up and running at home as its in the garage collecting dust and ive been relying on a blue commando i had fitted with the Tesla mobile connector until now.

    Please let me know your thoughts. I know the CAC does rise and fall but mine seemed to be falling pretty fast however Tesla reported on a recent service just after it fell 2 points that my battery was healthy so i thought it might just have been misreporting and would sort itself out. Im thinking range loss anxiety is the future lol.
     
  2. widodh

    widodh Model S R231 EU

    Joined:
    Jan 23, 2011
    Messages:
    4,822
    Location:
    Middelburg, The Netherlands
    Isn't this due to balancing of the pack? For the roadster you should slowly trickle charge it to a range mode charge en leave it there for a few hours.
     
  3. Perrin21

    Perrin21 Member

    Joined:
    May 18, 2014
    Messages:
    63
    Location:
    uk
    I have recently been charging and waiting for the balancing to be complete before driving away. Once the charge finishes (over 82%) i bring up the balancing screen and wait until i have all 0s on the display. It usually only takes about 10 minutes to complete. Hasnt really made much difference so far but its good practice so i will continue.
     
  4. widodh

    widodh Model S R231 EU

    Joined:
    Jan 23, 2011
    Messages:
    4,822
    Location:
    Middelburg, The Netherlands
    Was that one a range charge or standard charge?
     
  5. slcasner

    slcasner Member

    Joined:
    Feb 20, 2011
    Messages:
    563
    Location:
    Sunnyvale, CA
    I think it has more to do with the charging and driving pattern than it does with the difference between 70A and 60A charging (which I would not expect to cause any change in CAC).
     
  6. Perrin21

    Perrin21 Member

    Joined:
    May 18, 2014
    Messages:
    63
    Location:
    uk
    Standard charge
     
  7. widodh

    widodh Model S R231 EU

    Joined:
    Jan 23, 2011
    Messages:
    4,822
    Location:
    Middelburg, The Netherlands
    So I recommend you do a range charge on a regular 13A socket and leave it there for a couple of hours.
     
  8. hcsharp

    hcsharp Active Member

    Joined:
    Jun 7, 2011
    Messages:
    2,537
    Location:
    Vermont
    Good idea. Range mode charge does a little better job of balancing when it's done.

    I agree. The best way to get your battery out of balance (other than long storage periods) is to charge and drive. That's especially true on long trips.
     
  9. dhrivnak

    dhrivnak Active Member

    Joined:
    Jan 8, 2011
    Messages:
    2,150
    Location:
    NE Tennessee
    The CAC can and does vary. Mine dropped from 151 to 146 after I got the car and after a year before I learned how to pull and read logs. Since then I have seen it drift down to 143 then rise to 145.5 and now after the last trip it dropped to 141. Then in the last week it climbed to 142.5.

    So it will change and will drift down. Search for Tesla Owners Battery Study on Google and add your numbers and pull the records. See if your car is away from the pack. If not it is just likely random variation.
     

Share This Page