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.