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Interesting tidbit re: charge and range estimates

Discussion in 'Model S: Battery & Charging' started by scaesare, May 28, 2013.

  1. scaesare

    scaesare Active Member

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    There's been discussion within several different threads regarding the factors that influence how much charge is in a battery pack, how much range is left... etc... As I, and others have posted, lots of factors can make those estimates fluctuate slightly.

    I just installed my HPWC yesterday, and used it to charge last night for the first time. It completed with 238 miles of range estimated. I went to remove the charge cable from the car, and forgot I didn't have the fob with me, hence the car was locked. So while I pressed the button but was unable to remove the cable, it did wake up the dash screen.

    The estimated range immediately jumped from 238 miles to 243. And yet the battery had been doing nothing but sitting after charge had completed. It demonstrates to me that there's always going to be some variation in the estimate based on temp, internal variances within the pack, etc...

    Incidentally, this morning, after sitting during the rest of the night, it's back to 238. I assume no vampire draw on the pack now that shore power is supposed to supply the background electrical usage...
     
  2. joshuaeven

    joshuaeven Member

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    Seems like 238 is after a night's worth of vampire draw. That's what I leave with in the morning, usually down from 242 or so.
     
  3. stevezzzz

    stevezzzz R;SigS;P85D;SigX

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    Yeah, the release notes to 4.5 aren't totally unambiguous concerning what the car draws shore power for and what still comes from the traction battery, even while plugged in.
     
  4. scaesare

    scaesare Active Member

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    But my point was that after the charging stopped at 238, and had been sitting for a while, the estimate went UP.

    Just indicates estimates are... well... exactly that. And if anything the vampire draw should have reduced the estimated range left...
     
  5. dsm363

    dsm363 Roadster + Sig Model S

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    The car only seems to draw power when you ask it to do something (preheat or cool cabin). Just an observation though. Don't have outlet on meter or anything with V4.5
     
  6. FlasherZ

    FlasherZ Sig Model S + Sig Model X + Model 3 Resv

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    I noticed this behavior and reported it as well. When there is AC power present (contactor on, using "shore power" or charging), the range jumps up by 3-5 rated miles. 10 seconds after charging completes and the contactor is switched off, the range will drop back down.

    I was told that fixing that particular phenomenon was beyond the scope of a simple fix. I was trying to figure out whether it meant the battery wasn't being charged to its full SOC (e.g., it's really charging to only 236 miles which *looks* like 240 miles when AC is present) or whether we're just seeing bad numbers when AC isn't present (it's really got 240 miles but the calculations are a bit off). Then I decided 4 miles was too much to worry over and I wouldn't cut my trips that close. And a squirrel walked by and grabbed my attention away from that particular academic thought.
     
  7. scaesare

    scaesare Active Member

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    It is academic indeed... and why I think none of us need to get too caught up in a a few MPC difference form one charge to the next.

    But, after your observations, I'll have to test this again... I seem to think that when I pushed the HPWC handle button, the dash came on and the higher numbers popped up BEFORE I heard the contactor close. Of course, with the lock mechanism in the charge port, the contactor in the car, and the contactor in the HPWC head, who knows WHAT I heard. Not to mention it was nearly 1 am and after a cocktail. :wink:

    It wouldn't surprise me if shore power initially presents slightly higher voltage than the batt pack is maintaining... thus futzing with the range estimate...
     

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