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Reduced charging amps on J1772/Chargepoint EVSE's

Discussion in 'Model S: Battery & Charging' started by AWDtsla, Dec 30, 2016.

  1. AWDtsla

    AWDtsla Active Member

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    Up until today I've been blaming getting reduced from 30A to 22A on Chargepoint EVSE's to their crappy hardware. Although I think the latter is still true, I now believe Tesla is to blame, not Chargepoint.

    The car will reduce charging current whenever the voltage drop from start of charging exceeds 8%. Chargepoint does not specify wiring recommendations in their installation manual, however NEC code seems to recommend (not require??) a maximum of 5% voltage drop. So an electrician wiring up one of these EVSE's could (and it seems almost always does) leave the wiring at 5% voltage drop under load, and it would be a perfectly OK installation.

    What does this mean in real life? Well it means for most installations, the service voltage can't drop by more than 3%, or your Tesla goes into reduced charging current. It's even worse than that, because there's usually 25 feet of the J1772 cord, which also has voltage drop. I just measured the station I was plugged into, and the actual voltage drop from 0A to 30A is 6.77%. Which explains why it often drops to 22A, small normal fluctuations in service voltage are enough to trigger Tesla's algorithm. So now I babysit it, and as soon as I see 22A, I stop and start charging, hoping that the new lower starting voltage will hold it for a while, and it usually does if timed properly.

    This seems like another thing to add to the list of feature/functionality rolls backs attributed to CYA.
     
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  2. TexasEV

    TexasEV Well-Known Member

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    Maybe it's a problem that's specific to the stations you use? I've never gotten less than 30A from a J1772 except for a Blink station that had lowered the amperage when their defect was reported a few years ago.
     
  3. mrElbe

    mrElbe Active Member

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    Better to err on the side of safety than another sensationalist Tesla fire story by the news media.
     
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  4. AWDtsla

    AWDtsla Active Member

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    I'd say it's the opposite. You get lucky with your stations. You can scrounge plugshare/chargepoint for these stations that almost always drop to 22A. Even when I pull a steady 30A, I see how steep the initial voltage drop is, staying at 30A is purely luck.
     
  5. AWDtsla

    AWDtsla Active Member

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    So shapes apparently all new Tesla software updates. Anti-user changes to avoid bad press.
     
  6. AWDtsla

    AWDtsla Active Member

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    upload_2016-12-30_17-38-12.png

    See the dip in voltage and then the recovery? This is not the EVSE. This is service voltage, caused by some nearby industrial load. The spikes you see in the middle of the dip are me stopping/starting charging to get it to reset back to 30A.
     
  7. JPP

    JPP Active Member

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    I have had issues with a set of 4 Sema EVSE at one of the work locations I park at. First, 3 phase power, so baseline voltage should be 208V. However due to infrastructure, it is at about 202-204V. When I plug in alone, I see a voltage drop to maybe 195v or so. Still pulling 30A. if someone else plugs in, clearly the volts drop more, to about 188-192v, and then my charging current drops to 22A. Repeatable issue. I have asked the facilities engineer to have their electricians look into it. They did some fooling with taps on a transformer (???) with no real improvement. Just have to live with it. At another location (same owner) the 4 Sema EVSE see 238v at baseline with essentially no voltage drops. And I do see variable results with more 'public' EVSE elsewhere, depending on how abused the equipment (usually Chargepoint) is. I really believe that your issue is the infrastructure, particularly the wiring, supply voltage, etc, and not the fault of the EVSE (or Tesla). YMMV.
     
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  8. AWDtsla

    AWDtsla Active Member

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    If the infrastructure drops 5% or less from their main panel to the EVSE, then there isn't an facility infrastructure problem period. Even if it's more, I think that's subject to interpretation of the NEC if that's ok. So, 5%, plus the drop in the charging lead, plus some loss at the service, which closes in on the 8% mark already, and that doesn't include normal fluctuations in service voltage, which as far as I can tell no power company guarantees. Clearly we can exceed 8% total here.

    So, there is nothing wrong with the equipment or infrastructure, yet Tesla firmware drops charging current. It is Tesla's fault, it's their algorithm that's flawed.
     
  9. dhrivnak

    dhrivnak Active Member

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    I unfortunately frequently see low voltages on public charging. Fortunately the Roadster is not very sensitive.
     
  10. ggielen

    ggielen Member

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    It looks like this issue goes back a while. I charge at work, and charging almost always drops from 30A to 22A. It means the difference between a full charge (starting from around 20-25%) in one ~9hr work day at 30A, at ~190V, vs having to go back to the charge point the following day to top up, for a total of 12 hours of charging.

    I tried dropping the amps to reduce the voltage drop to 26A, but it doesn't seem to help much, I have too little margin to play with. Would increasing load at a smart point in the process somehow help? E.g. plug in, then run A/C on max while the car starts ramping up charging to increase voltage drop, and then turn it off, so voltage recovers. I don't know, grasping at straws here..
     
  11. AEdennis

    AEdennis Active Member

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    I consistently get at least 30A from @ChargePointnet public stations and always get it at my home CT-500 that I've had for over five years...

    The only time my rate drops is on the newer public EVSEs that split the service and drops the rate when someone else splits the charge...

    As others have mentioned YMMV. Perhaps your challenge is supply or your Tesla
     
  12. AWDtsla

    AWDtsla Active Member

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    Tesla has problems with installations done to code, it's difficult to blame the supply until Tesla fixes their software, as well difficult to blame an individual car for a problem the whole fleet has.
     
  13. AEdennis

    AEdennis Active Member

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    I have almost 83,000 miles on our 2013 Model S and have charged in public on a variety of public L2 chargers and have not experienced the challenges that you've mentioned. (as others have mentioned, expecting 24A at Blink stations, if and when I rarely charge there.) It might be premature to see what is causing these challenges for you. Have you reported the error to Tesla during your Annual Service?
     
  14. AWDtsla

    AWDtsla Active Member

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    I did talk to Tesla, and I got an email from Tesla engineering a long time ago on what their algorithm is, and that they refuse to change it to protect themselves from bad wiring. The problem with it is that it's wrong. You will drop current if voltage drops 8% from start of charge, at any point. NEC code allows up to 5% drop on a given circuit anyway, and then on top of that you have service voltage drops on either side of the meter. There's simply no headroom left to operate reliably at full current, on every good circuit. Of course, I already stated all of this is post #1.
     
  15. chillaban

    chillaban Active Member

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    There's one place that I charge where I pay $1/hr and the voltage drops to 180 as soon as I plug in, and then after it reduces to 22A, the voltage rises back up to 190 or so.

    Don't get me wrong, I wish for a "Please burn this place down if you have to, I don't own the place. I paid for 30A and I demand 30A at any cost" button. Doubt that's gonna fly well...
     
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  16. AWDtsla

    AWDtsla Active Member

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    Most of the time voltage drop doesn't indicate any danger.
     
  17. brkaus

    brkaus Active Member

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    I see this everywhere. But I agree with the conservative approach. ChargePoint could easily spec thier installations better.

    But the reason I agree with it is, in my area anyway, ChargePoint installations to simply be poorly maintained. If the three nearby, one hasn't worked in 4 months. Been reported several times.

    One drops 5% as it gets to 10A

    The third has a broken latch (reported several times over the past two months) allowing the plug to be removed while charging.
     
  18. brkaus

    brkaus Active Member

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    I'm at a ChargePoint now that started at 208v. Switched to 22 then 12a.

    At 12a it's now sitting at 190v.

    They really should be able to do better.
     
  19. JPP

    JPP Active Member

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    Chargepoint does not control the infrastructure at any installation. If the supply voltage is low, or the wiring inadequate, or there are other loads on the circuit, then you will see less voltage. And if the voltage sags during your charge session, your Tesla will dial back the amps by 20% for safety. So less volts times less amps means less watts. Don't blame Chargepoint.
     
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  20. ChargePointnet

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    @brkaus I'm sorry to hear you’re having trouble. We take support concerns seriously, and although it is accurate that we don't own the stations on our network, we do try our best to help station owners troubleshoot and fix issues. Can you send me a private message here with your email address? I'd like to escalate your feedback to the support manager for additional investigation.
     

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