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PSA: On CCS1/SAE Combo DC chargers, best to stop the charger BEFORE attempting to unplug

8310 Views 38 Replies 11 Participants Last post by  Sean Nelson
This only applies to DC charging over SAE Combo/CCS1/Combo1, NOT AC charging over J1772. Unless you KNOW the DC charger will EASILY (w/o excessive force, possibly flexing or breaking the locking tang on the handle), it it BEST to STOP charging BEFORE attempting to unplug a vehicle that is actively DC charging.

Possible methods to STOP first:
  • stop button on charger (not the handle)
  • stop button/action in charging network's app
  • stop button on the car's LCD (you may want to wake the car's or stereo's power button)
  • swiping your RFID card/NFC again (necessary on units like the ChargePoint CPE100 ( which don't have touch screens or physical stop buttons beyond emergency stop)
  • last resort: emergency stop button, if any

See Experience with Electrify America, as to why. If you don't, you may break the locking tang on the handle and you might even cause massive arcing if charging hasn't stopped when you pulled out. Or, the broken tang can be a hazard for the next user OR, the handle might be rendered unsuable until it's repaired.

There's been discussion of this before. Examples at Fast charger locked to my car and My Experience DC Charging overnight at hotel. There seems to be confusion, which is no surprise given that it can be different than J1772 AC charging on GM and many other vehicles.
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Gotta finally comment here, in an attempt to reduce the chance that a rookie EV-and-DCFC user will resort to using the emergency stop button on the DCFC. With a DCFC session in progress (not already ended due to being at 100%), a strong and long push on the big plug's button should, as I understand, cause the EV to command the DCFC to bring the charger's DC current down to zero. Once that is done the Bolt will open the little shiny tab that is locking the big plug onto the Bolt's receptacle. The other ways of stopping the DCFC session and bringing the DC current to zero as already described above are also fine, of course.

In my experience this strong and long push on the plug's button might take 3 seconds, and if there is not too much ambient noise it might be possible to then hear the DCFC winding down (cooling fan?). That would confirm the DC current is down at zero and so now a pull would work to safely remove the plug. Could also bend down and look for that shiny tab to be in the up position to confirm that the lock is not in effect any more. The Bolt's design with this shiny locking tab is meant to hold the big plug in place and so prevent the user from interrupting a high DC current (an arc) by somehow forcing the plug off when the current is still above zero.

My purpose of preventing use of the DCFC's emergency stop button is due to the possible long recovery time to get the DCFC unit re-set and ready for the next user. It might, on non-communication-equipped units, require a site visit by a service provider. Some units may have an emergency stop button that, once used, can be rotated to do a re-set right there and then.

A related tip is that if the DCFC cable is short or the EV's port is not close enough to the DCFC, there might be a lot of "side-pull" of the big plug against the EV's receptacle. The resulting plastic-on-plastic friction might make it seem that the plug is still locked onto the car even after it is clear that the session was properly stopped. Relieve the side-pull and try another pull. Happy DCFC-ing!
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Yes, emergency stop shouldn't normally be used.

As for strong and long push, FWIW on the BTC Fatboy charger in the movie in post #3, I was surprised by the very fast, almost immediate release upon a quick and not strong press at all. It was almost identical in feel to just use J1772 AC handles (except those don't cause Bolt's silver locking tab to engage or disengage).
I learned about the long push for a DCFC situation only after having a problem releasing a DCFC plug on my first road trip. My usual short button push like on a J1772 plug, and then pull, did not work for this rookie. Should have known better. In a L1 or L2 session the Bolt allows the J1772 to be pulled off very quickly (maybe the shiny tab is not even in a locked position for a J1772 session - have never really checked) - because interrupting 32 A of AC current is not a big deal. On the DCFC the DC current needs to be respected - by getting it down to zero A.

If some DCFC units take the DC current down to zero very fast, that could be why some DCFC users have experienced a quicker plug release - perhaps a faster DCFC control circuit than I have experienced, or the DC current was already closer to zero.
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