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Discussion Starter #1
We have a 2017 ED and a ChargePoint Home charger which can be set to start charging at 7pm when the hydro costs drop.
About 50% of the time the charge does not start at 7pm, sometimes it is delayed about 40 minutes and other times it waits until the wee hours of the morning. The on-board "smart charge" is not set.
Anyone know why? ChargePoint have checked the charger and even sent a new one. Mercedes doesn't respond and the dealership seems baffled.
Frank.
 

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We have a 2017 ED and a ChargePoint Home charger which can be set to start charging at 7pm when the hydro costs drop.
About 50% of the time the charge does not start at 7pm, sometimes it is delayed about 40 minutes and other times it waits until the wee hours of the morning. The on-board "smart charge" is not set.
Anyone know why? ChargePoint have checked the charger and even sent a new one. Mercedes doesn't respond and the dealership seems baffled.
Frank.
User settings in the instrument cluster may be overriding the Chargepoint chargers' ability to start charging at the times you have set on it. Have you checked your user settings in the smart's instrument cluster?
 

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Discussion Starter #4
Yes I have. There are no settings on for 'delayed charging' or "climate control" (although the user interface for that section is a bit muddled). Also the behaviour is apparently random: sometimes starts at precisely 7pm (or a few minutes after); sometimes after 40 minutes or so and sometimes after 8 hours or more. Furthermore if the car is connected during the day (during an on-peak time) then it is possible to command the ChargePoint to "start now". Sometimes it does and sometimes it doesn't. When it doesn't it is then possible to get the car to accept the charge by unlocking the door (and nothing else!).
 

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Yes I have. There are no settings on for 'delayed charging' or "climate control" (although the user interface for that section is a bit muddled). Also the behaviour is apparently random: sometimes starts at precisely 7pm (or a few minutes after); sometimes after 40 minutes or so and sometimes after 8 hours or more. Furthermore if the car is connected during the day (during an on-peak time) then it is possible to command the ChargePoint to "start now". Sometimes it does and sometimes it doesn't. When it doesn't it is then possible to get the car to accept the charge by unlocking the door (and nothing else!).
If your settings look like the following pictures, then the culprit for your charging troubles are likely to remain with the charger you are using or your electrical circuit.



 

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Discussion Starter #6
Thanks. The settings are precisely those shown. "No preselection".
However the charger and the cable has been replaced without any difference. ChargePoint have been highly commendable in their level of support.
Sometimes the car will start at the low tariff point. if we plug it in before. If we command "start charging now" over the net using the ChargePoint app sometimes it will and sometimes it won't.

If charging does not start when expected (or when commanded), then we can force it to start by 'unlocking' the car (!). This suggests that the charger is offering power, but the car simply does not want to accept it once the flashing orange light next to the J1442 goes off .

So the sequence is:
Plug in. Orange light flashes for a few seconds then goes out. ChargePoint display shows "car connected" both on the charger and remotely.
Apply power either by awaiting low tariff or by override command to ChargePoint charger. Sometimes it starts charging and sometimes not.
Then: either 'unlock' the car, which will always start charging, or simply wait (and it usually seems to start sometime... anywhere between 40min and 8 hours later, which is just slightly nerve wracking if you anticipated going out later in the evening).

F.
 

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Thanks. The settings are precisely those shown. "No preselection".
However the charger and the cable has been replaced without any difference. ChargePoint have been highly commendable in their level of support.
Sometimes the car will start at the low tariff point. if we plug it in before. If we command "start charging now" over the net using the ChargePoint app sometimes it will and sometimes it won't.

If charging does not start when expected (or when commanded), then we can force it to start by 'unlocking' the car (!). This suggests that the charger is offering power, but the car simply does not want to accept it once the flashing orange light next to the J1442 goes off .

So the sequence is:
Plug in. Orange light flashes for a few seconds then goes out. ChargePoint display shows "car connected" both on the charger and remotely.
Apply power either by awaiting low tariff or by override command to ChargePoint charger. Sometimes it starts charging and sometimes not.
Then: either 'unlock' the car, which will always start charging, or simply wait (and it usually seems to start sometime... anywhere between 40min and 8 hours later, which is just slightly nerve wracking if you anticipated going out later in the evening).

F.
The unlocking the door aspect was missing, but crucial. Sounds to me like the car goes to sleep and needs to wake up. Maybe the Chargepoint isn't sending a signal that the car is receptive to with perfect compatibility. May want to place a call to smart's customer assistance center to ask for some help, but at the end of the day the Chargepoint charger has the burden of finding a solution to your issue.

Sounds like they tried by sending you a replacement charger, but it is probably not as compatible as you would have hoped it to be. It's an aftermarket charger. See if CAC has an update for you, but otherwise you may be hitting the end of the road and can try a different aftermarket charger to see if that changes things for you.
 

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Discussion Starter #8
Thanks, although I am not entirely convinced. Using the j1772 circuit below:

the only signalling between the car and the charger is carried over the two wires marked Pilot and Proximity, pins 4 and 5. The latter is the signal to the car that a charger is connected. S3 is the microswitch in the J1772 that will turn off the power (on the pins 1 & 2) before disconnect. The Pilot carries the 1kHz signal to indicate the power available from the charger, and permits the charger to determine that a car is present (which would close relay K2). All of these functions are working correctly as far as can be determined without taking it all apart.

Your suggestion that the car "goes to sleep" is probably the correct one. There is no doubt that when it "wakes up" the charging proceeds as normal. Under normal circumstances the car commands the energy flow once the charger signals readiness apply power. Personally I don't think the attribution of blame to the charger is justified since the "wake-up reset of unlocking the door" initiates the entire sequence - it surely would not do that if the charger had "lost interest". It looks as if relay K1 might be dropping out. Earlier in this discussion forum there was suggestion that the Climate Control did not work reliably in North America, but it is not clear whether that software bug was fixed either, and if not it would be related to the one that I report here.

I will send a copy of this to ChargePoint for their comment. Thus far they have been much more responsive than Mercedes, and very probably have considerably more experience of the implementation of the j1772 protocol across many makes of car.
 

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Discussion Starter #9
Here is the response from ChargePoint:

Hello Frank,

Thank you for reaching back out to ChargePoint Support.

Yes, the ChargePoint home follows the SAE J1772 standard; but it is not a data transfer at all.

You're correct, when the delay timer is set on the ChargePoint Home station; it will block any charging requests until it's scheduled time. If it changes to the scheduled time, allow any requests to come through. If there are no requests (meaning the car has some sort of time-out built into its software after a certain amount of attempts or time-frame that it stops attempting after failed attempts) at that time, charging won't take place until something is triggered on the vehicle's side to retry that request (unlocking the doors, opening the doors, etc).
Best Regards,
Trevor C.

ChargePoint Support
 

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Discussion Starter #10
So let's review the handshake sequence, using the schematic I posted earlier for a reference:

Plug in the charger j1772 connector. This applies 12V to pin 4 through a 1K resistor. The voltage drops to 8.8V.
Car detects this and closes K1, places R2 in parallel with R1 which drops the voltage on pin 4 to 5.6V
Charger detects this lower voltage and closes relay K2 which sends the 1KHz signal to the car. It also applies 240V power
Car sees the 1KHz signal, computes the charging current and displays the length of time to charge.

If the car is set for "climate control" then it does not close K1 until later. The charger will wait patiently for that to happen.

If the charger is set to wait for low tariff, then it does not close K2 until later (which either happens at low tariff or on demand by internet command). The car should wait patiently for this to happen.

What appears to happen some times in my case is that the car reverts to some arbitrary delayed state (which is why the check of whether the climate control was set was important). A reset (by opening the door) will force it out of the state.

We now have the design criteria for a simple test rig. See next post.
 

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Discussion Starter #11
Here is a simple test rig, using just three connections to the j1772 on the car, pins 3 (ground), 4(the "Pilot pin") and 5 (Proximity).

Pin 5 is returned to pin 3 through 150ohm (the proximity sensor). A more sophisticate rig will simulate the switch in the j1772 handle.
Connect +12V through a 1Kohm resistor to pin 4, with 0V on pin 3. Measure the voltage. It should be 9 +/-1 V
When K1 in the car closes the voltage will drop to 6+/-1 V
If K1 subsequently drops out for any reason the voltage on pin 4 will return to 9V This means that the car is unable to be charged. Unlocking the door will reset it.

Has anyone else reported this problem with a low-tariff charger? Does Mercedes use a simple diagnostic test rig like this? Where should I take this problem next?

Thanks,

Frank.
 

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Discussion Starter #12
Here is a simple test rig, using just three connections to the j1772 on the car, pins 3 (ground), 4(the "Pilot pin") and 5 (Proximity).

Pin 5 is returned to pin 3 through 150ohm (the proximity sensor). A more sophisticate rig will simulate the switch in the j1772 handle.
Connect +12V through a 1Kohm resistor to pin 4, with 0V on pin 3. Measure the voltage. It should be 9 +/-1 V
When K1 in the car closes the voltage will drop to 6+/-1 V
If K1 subsequently drops out for any reason the voltage on pin 4 will return to 9V This means that the car is unable to be charged. Unlocking the door will reset it.

Has anyone else reported this problem with a low-tariff charger? Does Mercedes use a simple diagnostic test rig like this? Where should I take this problem next?

Thanks,

Frank.
 
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