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Only 70 AMPs at Supercharger

Discussion in 'Model S: Battery & Charging' started by WannabeOwner, Aug 19, 2016.

  1. WannabeOwner

    WannabeOwner Member

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    Newbie to supercharging ...

    ... went to airport to collect daughter last night, typical of UK half the highway structure closed / blocked off ... probably just to clean the drains ... nightmare!

    I only intended to stop at one supercharger, on the way to airport, but the predicted delay on the return journey was so long I changed route to come home a different way, 30 miles longer, so I added an extra Supercharger stop on the way home.

    According to Teslafi :

    1st Supercharger 10:08 PM to 10:22 PM (13 mins), from 75% to 88%, added 10.9 Kwh, efficiency 95.1 % - 400V, 176A falling steadily to 148A. One other car charging at the same time (not at an adjacent stall)

    2nd Supercharger 1:30AM to 2:02AM (32 mins) from 32% to 49%, added 13.84 Kwh, efficiency 104.2% . 148A initially but fell to 82A within a few minutes, and then stayed there. 360V. I think there were about 10 stalls, but several of them were covered with plastic covers. No other cars charging.

    External temperature 17C both times

    (Graphs attached from Teslalog)

    I started at lower SoC 2nd time, so would have expected faster charging?. All driving was at 70 MPH speed limit with Range Mode on - so no high-speed-driving etc. as a cause. Any explanation for that? something i should be aware of / do differently next time? (Clearly checking the charge rate would have been sensible!! but I "just assumed" it would be max-rate).

    Annoying thing is that I could have carried on and charged at the first supercharger on the way home ... I thought I would try a different one and if, for any reason, it was not working I could carry on to the second - whereas if I went to the second there would have been no other option. Another factor was that Coffee Shop might have have been closed by the time I got to the 2nd one!!
     

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  2. Rocky_H

    Rocky_H Member

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    Yeah, that second case (the one shown in your picture called SC02.jpg) is not running right at all. @Bighorn has mentioned a helpful easy to use rule of thumb that you can use the sanity check the operation of a Supercharger to see if the charging rate makes sense versus your state of charge. Set your display units to "Energy", instead of "Distance", so your range shows as a %, and the Supercharging power shows in kW. Add together your state of charge and the kW power. Those should generally add to about 120-130ish through most of the range of charging. Notice on your first one (SC01.jpg), a sample value is 80% + 50kW = 130. That's about right. On your second one, the values are like 39% + 26kW = 65. That's not even close, so the Supercharger is not putting out the amount of power it's supposed to. You should call the Tesla Supercharger support phone number that is posted on the stalls right then to let them know, preferably while it's still going on, so they can see it.

    This rule of thumb value of 120-130 is right for the 85/90 battery sizes. I don't remember if the value is a little different for the 60/70/75 batteries.
     
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  3. WannabeOwner

    WannabeOwner Member

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    Very useful rule-of-thumb, thanks. Bottom line is that next time I'll check that it IS charging at the full rate, and perhaps try moving to a different stall if not.
     
  4. Electric700

    Electric700 Member

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    The second time you charged, did you try a different Supercharger stall when you saw the lower current? Also try charging with Range Mode off since that may reduce cooling power.
     
    • Informative x 1
  5. David29

    David29 Member

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    The OP also did not state whether or not his car was paired with another car at the second charger. As you are a newbie, be aware that you will get a lower charging rate if you are the second car at a pair of charging stalls. So if someone is using 3A, try to avoid 3B, and so on.
     
  6. Rocky_H

    Rocky_H Member

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    ...except for the part that said "No other cars charging."
     
  7. David29

    David29 Member

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    Oops, my bad. Guess I should have read more carefully! Thanks!
     
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  8. apacheguy

    apacheguy Sig 255, VIN 320

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    There are a number of threads on this. The bottom line is we don't know why certain SpC cut back under certain conditions.
     
  9. WannabeOwner

    WannabeOwner Member

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    Stupidly no :(, went off to get a coffee and have a pee, didn't really look at the charging rate (or know what a "good rate" should be) when i got back, so I just sat there until I had enough charge, it was only when I looked at the Teslafi graphs the following morning that I saw the difference. I'll know better next time - it will be interesting to see if changing to another stall, if it happens to me again, will give a different result.

    I had Range Mode on, so that might well have been a factor. Would I need to turn that off some time before reaching the supercharger so that the battery temperature starts to fall [with active cooling], or is it sufficient to turn off once reaching the supercharger, and put back on again when i leave?

    I'd only been driving an hour at the first charge, would have been nearer three hours total by the second charge so battery might have been warmer? also battery was at a lower state of charge - I don't know if it generates more heat [to extract the same power] as the SoC reduces? (No high speed driving to account for battery heat)

    Looking at the graphs it appears to me that nothing happened for the first few minutes. That doesn't seem to tally with what the dashboard suggests, is it just an artefact of the API? If not doesn't it make a splash-and-dash ineffective?
     

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