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Thread: range questions

  1. #1

    range questions

    Just got an 08 roadster. It'll be a week or so before I get it on the road, so I can't really cycle it up and down yet (only up, by charging it.) It hadn't been charged in a long while, but was not totally dead. Using the 110 mobile connector (that's all I have right now,) it took a charge in standard mode, only to 139, then to 148 ideal miles, then in the range charge mode, to 172 ideal miles. From everything I've read, that's still very low. Scares me. But here's a few things I don't understand; the battery icon appears 7/8 full, and the range showed on the odometer display shows only 98 miles of standard mode range. I know the car figures in the way it was driven the last 40 miles (previous owner,) but that drastic of a difference between the 172 and 98? With use and charging, should these ranges come around? Anything I should do in the meantime other than just leaving it plugged in?

  2. #2
    First: don't worry about the estimated range (the 98 mile thing). It depends very heavily on how it's been driven recently. I never look at it at all, I find that I do a better job of estimating by knowing how the car works and what kind of driving I'm planning on doing.

    The numbers you're quoting for full charge are very low. However, a car that's been sitting unplugged for a long time will be horribly out of balance (some of the cells will have more charge than others). I had the same problem when I had my battery replaced with one that had been unused for a while. The thing to do is to charge it to range mode full and let it sit plugged in for a long time. For my new battery it took 4 or 5 days to fully balance. Yours may take even longer. What you'll see is that as it balances if you start it charging again it will charge to higher and higher values until it's through balancing. It theoretically balances in standard mode, but I think it doesn't work that well.

  3. #3
    You can't know how much energy the battery can hold unless you both deep discharge it and fully charge it.
    If you have a large container that you can not see inside, and you repeatedly pour 1 cup of water out and then back in - how much can it hold?

    I think you should do a few range mode charges and discharge it as deeply as you feel comfortable between each one.
    Until two range mode charges in a row top out at the same number of ideal miles - continue cycling it this way.
    Once that is done you should have a good idea of what the battery capacity is.

    The battery needs to
    1) balance the cells
    2) figure out where the bottom is
    3) figure out where the top is

    Please report your results.Take log files and use a log file parser to analyze them.

  4. #4
    Senior Member markwj's Avatar
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    +1 Bolosky's advise

    Leave it plugged in (even if you can't drive it), and it should balance as best it can.

    It would be good to _exercise_ the battery, once you've got it on the road.

  5. #5
    Senior Member markwj's Avatar
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    Quote Originally Posted by chris22104 View Post
    It hadn't been charged in a long while, but was not totally dead.
    I would _love_ to see the log files on this car. It would tell us a lot about how the 2008 cars behave when not plugged in for extended periods. Given the recent 'bricking' news, this would be very useful. It would also let you know if the battery ever went to 0% SOC (or lower), and some more about the history of the vehicle.

    To get the logs use a USB stick (2GB or less would be best) and add a folder named “VehicleLogs” to the root, plug it in, turn the key on and off and watch the screen tell you it is downloading the logs. It takes about 15 minutes to get the logs from the vehicle onto the stick, and the car VDS will tell you when done. The logs are stored in a ".gz" file in the VIN subdirectory of VehicleLogs.

    Would you be willing to send me the log files? In return, I'll send you back the results of what we can see with the log file analysers. PM me if you manage to get them.

    Regards, Mark.

  6. #6
    If you pull a log file from the car and use the analyzer from this thread: Roadster Owner Based Study of Battery Pack Capacity Over Time

    One of the sections of output is the estimated amp hours capacity of the bricks in the battery - it includes the average of all bricks, and the amp hours of the weakest brick.
    Those estimates are recorded every day - it would be very interesting if that estimate slowly becomes more conservative over time as the car sits unused.

  7. #7
    Thanks for the replies guys. I've initiated 3 standard charges over the last 5 days that I've had it (139 IR, up to 148 IR, as I'd indicated.) Then yesterday around 4pm, I hit it with the range charge (took about 6 hours more, and got up to 172 IR.) I guess I should have left it alone at that point, but right after the ring went to green, I unplugged it for 5 minutes to start it and look at all the driving screens to see what I could see. Then I plugged it back in, in the standard mode (ring still green,) and there it sits. I'll leave it plugged in and not start another charge cycle until I can drive it.
    And I'll see about getting the log files, and PM them to you Mark (thank you.) Give me a few days.
    I should have it on the road in a week or so. You guys mention discharging it fairly deeply. With an ideal range of only 172, how deep should I go, and should that be driven in standard mode? Then I'll do another range charge as you'd suggested, and see where it is at that point (and report back with the results.) Thanks again guys!

  8. #8
    Senior Member markwj's Avatar
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    I don't think anyone here will know exactly what to expect, but the real world experience is here.

    I would suggest you take it easy on the pack for the next few weeks, not taking it anywhere near zero until you know more about how it is, and keeping it plugged in whenever it is not driven. That should give the car the most opportunity to heal (and balance) itself. Then, start to exercise the battery across its SOC range.

    Jeez, that sounds like post-surgery advise! Don't forget plenty of fluids - actually, it may be worth checking fluid levels too
    PLEASE NOTE:
    These musings are the copyrighted intellectual property of the author, and are intended as part of a conversation among the Tesla Motors Clubs membership.
    My words may not be quoted by any third party outside the Tesla Motors Clubs forums, without my express consent.

  9. #9
    Roadster #1144 + Sig 114 dsm363's Avatar
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    Have you had a chance for Tesla to service it and do a battery test? That does seem like a low number on the ideal range.

  10. #10
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    A battery this out of balance could easily take a full month to balance, leaving it plugged in every second you aren't using it. When they replaced my battery (due to some defect found during a normal diagnostic), my standard charge was a good 40 miles less than my previous battery, despite assurances that the new battery had cells that were the same age or less as my old battery. Tesla's instructions were to leave it plugged in all the time, and the battery would balance itself at a rate of about 1 ideal mile per day. They were correct. Eventually, I got all those miles back and then a few more. Now it always charges up in the low 180s (standard). Tesla could tell you for sure by doing a test, but most likely you'll be able to remedy the problem over time.

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