ChargePoint Charging Question

[coulomb]

The issue of slow charging after the pause has been escalated, hopefully to someone within ChargePoint who understands pilot signals and possible interactions with MiEVs.

Excellent! Maybe the engineers still won't listen, but at least they'll hopefully now be aware of the issue.

 

[kevin1956murray]

Unfortunately for me, ChargePoint help line operators have been instructed to not do remote rebooting. Apparently this causes loss of the 'history data' of that station. So I no longer have a workaround for when charging resumes at just 1.1kW.

Fortunately I have not yet experienced the low rate on ChargePoint's older single cord stations. So I charge at those now if possible.

 

[JoeS]

So, yesterday at an EV workshop fostering EVs where I displayed my i-MiEV and answered questions from interested attendees, I asked a technically-savvy acquaintance from ChargePoint regarding this reduced-power phenomenon we've been seeing after the i-MiEV does a 'timeout'.

Basically, he said their EVSE has no ability to reduce the power supplied to the car, as the EVSE sets a maximum power level that can be drawn from that station and it is the car itself that dictates how much it draws.

About all he could offer is that some dual-station EVSEs which share a common line may provide less power if another car is charging, but that has nothing to do with our 'timeout'.

Another thought occurred to me, since many of us have not experienced this problem: could it be related to the model year of our i-MiEV? What prompts this question has nothing to do with this ac charging, but I seem to recall that there were some later-model-year i-MiEV compatibility issues with some CHAdeMO chargers.

kevin1956murray, I may have missed it if you said it, but which model year is your car?

BTW, wouldn't simply unplugging the car and starting a new session solve this also?

 

[JoeS]

Oooh, another thought, in addition to what I just wrote above. I just remembered that we had a factory Recall late in 2012 that was related to the Clipper Creek EVSE but it also affected the i-MiEV 'timeout'. IIRC, it reduced that timeout to as little as 6 minutes instead of the previous 10 minutes.

keving1956murray, is your car up to date with all the recalls?

Has anyone ever figured out what the algorithm is for what triggers this 'timeout' or its duration, as both seem to be all over the map. I think we had some discussion in the past year...

 

[kevin1956murray]

To answer the questions just above: My MiEV is 2012, and as far as I can tell there are no open recalls on it. (Or it could be that the website I used just looks for open "safety" recalls by VIN.

My understanding is that the pilot signal (frequency) informs the car what the maximum charging rate can be. The pilot signal comes from the station. On single cord Chargepoint stations my car goes right back to 3kW after the pause, each and every time. There is something about dual cord Chargepoint stations that results in 1.1kW charging after the pause. It is disappointing to me that a Chargepoint presenter would blame the low rate on the car, since I have provided Chargepoint with many traces showing the recovery to 3kW on their older single cord stations.

 

[kevin1956murray]

And to answer the other quest: Yes physically unplugging and reinitializing a session does get back to 3kW (until the next pause). But the chargers I use are about a 12 minute each way bike ride from my house, so riding back just to fix this continuing problem is not a preferable work around.

 

[JoeS]

My understanding is that the pilot signal (frequency) informs the car what the maximum charging rate can be. The pilot signal comes from the station. On single cord Chargepoint stations my car goes right back to 3kW after the pause, each and every time. There is something about dual cord Chargepoint stations that results in 1.1kW charging after the pause. It is disappointing to me that a Chargepoint presenter would blame the low rate on the car, since I have provided Chargepoint with many traces showing the recovery to 3kW on their older single cord stations.

Not to worry, I'll continue working the problem with my acquaintance directly, and just sent him an email with some questions about the logic implementation in those dual-port ChargePoint EVSEs which are fed by a single (limited) circuit.

Another confusing factor: in the situation we have, the car only gets 1.1kW vs. its previous 3.0kW. Say, 3kW is about 230vac at the car's usual 13A draw, so the 1.1kW is about 4.8A at that voltage. That's a strange number, especially if the EVSE is being fed by a single 40A circuit. Kevin, any chance you can access the circuit breaker panel for that EVSE to see what the amperage is on that breaker?

If anyone in the SF Bay Area has experienced this, please let us know as my acquaintance has offered to take their diagnostic instrument and check the station (and car's) performance directly.

Has anyone else other than jray3 seen this specific problem at a ChargePoint station?

Last night while attending a concert far from home I charged at a ChargePoint dual-port station with no one at the other plug, but, darn it, my car didn't do its 'timeout' so i couldn't duplicate the problem.

Regarding the Clipper Creek Update:

To answer the questions just above: My MiEV is 2012, and as far as I can tell there are no open recalls on it. (Or it could be that the website I used just looks for open "safety" recalls by VIN.

Not to worry, and it most probably has nothing to do with the problem you're seeing. The next time you're by a Mitsubishi dealer ask them to check your recall status. I just found the Mitsubishi "Customer Satisfaction Campaign SC-13-001 dated February 2013 regarding Clipper Creek EVSE: " This incompatibility is caused by a software mis-communication between the i-MiEV EV-ECU and the charger..." The fix is to update the EV-ECU with the latest programming. Free.

 

[kevin1956murray]

The dual cord stations that I use are at Amplify Credit Union, or Whole Foods, or an apartment complex parking lot. I do not know where any of those breaker boxes are, and even if I did I'm pretty sure that no one would want me opening the panels.

I would be interested in knowing the frequency of the pilot signal at both a session start and 6 minutes into a pause, but I don't know how to access that either, let along not having a meter to measure it.

 

[JoeS]

I would be interested in knowing the frequency of the pilot signal at both a session start and 6 minutes into a pause, but I don't know how to access that either, let along not having a meter to measure it.

The problem commences after the car decides to cease its 'timeout', which seems to be variable and can last between six minutes and about 20 minutes. Infuriating if we're on the road...

Has anyone tried to measure that pilot signal? Not that this has anything to do with this ChargePoint problem (or does it?), but our Mitsu EVSE is evidently not J1772 compliant. My Tesla will not work with the Mitsu EVSE.

Here's a nice discussion of the J1772 interface: https://en.wikipedia.org/wiki/SAE_J1772

Edited once.

 

[kevin1956murray]

Below is the part from that Wikipedia link that indicates to me that the pilot signal from the station indicates to the car how much current can be drawn:

"Control Pilot (Current limit): The charging station can use the wave signal to describe the maximum current that is available via the charging station with the help of pulse width modulation: a 16% PWM is a 10 A maximum, a 25% PWM is a 16 A maximum, a 50% PWM is a 32 A maximum and a 90% PWM flags a fast charge option.[23]

The PWM duty cycle of the 1 kHz CP signal indicates the maximum allowed mains current. According to the SAE it includes socket outlet, cable and vehicle inlet. In the US, the definition of the ampacity (ampere capacity, or current capacity) is split for continuous and short term operation.[23] The SAE defines the ampacity value to be derived by a formula based on the 1 ms full cycle (of the 1 kHz signal) with the maximum continuous ampere rating being 0.6 A per 10 µs (with the lowest 100 µs giving 6 A and the highest 800 µs giving 48 A).[22]"


I have a theory that when a MiEV pauses, the Chargepoint software assumes that the car is done, and modifies the pulse widths of both cord's pilot signals so that more current can be supplied to the other cord, if a new session were to start on that other cord.

 

[JoeS]

"... and the highest 800 µs giving 48 A).[22]"

Interesting, as I've drawn as much as 70A from J1772 with my dual-charger Tesla S85. For example, I got close to that in Iraan TX https://www.plugshare.com/location/19815

I have a theory that when a MiEV pauses, the Chargepoint software assumes that the car is done, and modifies the pulse widths of both cord's pilot signals so that more current can be supplied to the other cord, if a new session were to start on that other cord.

Agree with you, and that is almost exactly the question I posed to my ChargePoint acquaintance. Let's see what he comes back with.

 

[JoeS]

Burrowing down further into the details, on the January 2019 ChargePoint plot (February 2, 2019 post), is it safe to assume that the jump from 1.1kW to 3kW occurred when the car using the adjacent port unplugged? Fair to say that did something which allowed the i-MiEV charger to go back to full power draw?

 

[kevin1956murray]

Looking back at that, I would say that it is very likely that the other car unplugging might have caused the station to adjust (and refresh) pilot signals, and that is what likely caused the charge going back to 3kW. Too bad that station has such low usage, otherwise others plugging out could often be my workaround to get away from the funky 1.1kw slow rate.

 

[kevin1956murray]

Thanks to Joe S's digging into details, and the new theory that a neighboring car unplugging from a shared station might cause a MiEV charging to move from the funky 1.1 kW "post pause" rate back to 3 kW, it occurs to me that I might be able to replicate that in a controlled fashion.

I have the 2012 MiEV and a 2011 Volt, so I can use the Volt as the 'neighboring' car. So soon I intend to catch a time when the MiEV is down at 1.1kW, and go see if I can affect that rate by plugging the Volt in and out on the other cord, without touching the MiEV cord.

I plan to leave the Volt plugged in at least 10 minutes, since the 'trace' read points are only every 5 minutes (after the initial ramping up).

Hopefully the neighboring car does not need to be drawing more than 3kW, since that is all that the Volt will take.

 

[JoeS]

Kevin: check your Private Messages - I sent you a PM asking for the latest ChargePoint ticket number. Thanks.

 

[kevin1956murray]

Today a drove a little extra, to discharge the battery enough where for sure it would pause during charging, and I plugged in at a dual cord Chargepoint station. I had planned to plug in my other car once the MiEV had paused and dropped to 1.1kW, but it turns out the other cord was put in use before I had a chance to do that. So then the experiment changed to just monitoring if the MiEV rate would go up when the "Find Stations" screen showed that the other cord was available.

So I monitored that, and oddly, my charging rate went back to 3kW a few minutes before that cord showed as available. (I intend to attach screenshots below). It is possible that that car had then fully charged, and then 5 minutes later the owner unplugged it. Or it could be there is a several minute delay on station availability updates, compared to charge rate data updates.

Anyway, the increase back to 3kW appears to be definitely related to the other cord changing from charging to not being needed.

I think when that happens, the Chargepoint dual cord stations adjust the pulse widths of the pilot signals, likely in a attempt to get more charge to the active vehicle. So when the MiEV pauses it charging, the station kind of gives up on it, and indicates to the MiEV that it will only give it 1.1kW. It will hold that way until the session physically reinitialized, or the station is rebooted, or until a car using the other cord stops needing a charge.

I plan to suggest to Chargepoint that they make the stations reanalyze each cord more often, since at 1.1kW the station should be able to sense that that car still wants to charge, and maybe could pull more than 1.1kW if the pilot signal were to allow it.

12:31PM when power came back: Both cords show still "in use":

12:37PM after another 'every 5 minute' read point: Other cord shows as available:

 

[ChrisEV]

I'm in Canada but my 2012 i-MIEV doesn't have this problem and I have tried many chargepoint units around the city. Is there a specific ChargePoint model# this happens at?

But my car has done the timeout many times at a ChargePoint station, it usually happens If I arrive with 20% or less, it will timeout at around 36%, ChargePoint will actually terminate the session remotely now if it goes on too long, about the time that the car pauses charging. Even though the CP app says the session ended my car resumes charging.

If it's only dual-chargers it may be that the voltage is too low, all the public chargers I've tried my car pulls 208V/14A. I've seen the voltage as low as 205V and the current is 14.1A at most if I recall.

I've seen comments on PlugShare in the area that the Leaf refuses to charge at some public stations that drop below 200V but I was able to use them no problem.

Just some ideas.

 

[kevin1956murray]

I do not know any Chargepoint station model numbers, but on all four dual cord Chargepoint stations that I have tried, all four very dependably change to just 1.1kW after the pause. The single cord Chargepoint stations dependably return directly to 3kW.

 

[ChrisEV]

I do not know any Chargepoint station model numbers, but on all four dual cord Chargepoint stations that I have tried, all four very dependably change to just 1.1kW after the pause. The single cord Chargepoint stations dependably return directly to 3kW.

These are the shared power stations correct? There's stations that will share 6.6kW of power between 2 cars and ones that will provide 6.6kW max to 2 cars plugged in.

I've used both, I don't think I've had the pause happen on the shared power variant now that I think about it.

 

[JoeS]

OK, so here's where we stand. In a few email exchanges with this acquaintance, he, on his own and not part of any official ChargePoint response, preferred to take the empirical approach and first measure what the pilot is telling the car and how the car is responding. Evidently, there have been significant issues with other manufacturers (i.e., cars not complying with the J1772 spec) that this is the logical first step.

To that end, what I intend to do is, when running low on charge, seek out a dual ChargePoint station and plug in and monitor the charge (using the ChargePoint app) to see when I get a 'timeout' and what the response is after the 'timeout' goes away. If I can make the problem occur then I will contact my friend and we can get together so he can attach his instrument and we can measure the pilot and car's power draw. He's really interested in seeing what the EVSE pilot signal is commanding in our situation. Even though we're convinced it's the EVSE, this test will conclusively prove or disprove this supposition. Come to think of it, I'll ask him if they have a dual-port EVSE at ChargePoint's HQ as I can drive down there to do this test.

The hint by ChrisEV that the timeout occurs at 36% is a great clue, as I had previously never been able to understand when this occurs.

Independently of that, kevin1956murray, perhaps send an email to ChargePoint's customer service and simply ask for a status on that last open 'ticket' you have?

Now, during my email exchanges my friend said that if anyone is interested in measuring an EVSE pilot then here's a relatively-inexpensive kit to do that:
https://www.tindie.com/products/nsayer/evse-tester/
The issue I see is having to make a J1772 breakout cable to be able to tap into the signal while using the EVSE without actually opening up the box to do that.

'Nuff for now, as I'll be driving over 150 miles in my i-MiEV today and need to do my EVSE availability homework...