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At less than 80% SOC, the charging rate is much faster than if the SOC was above 80%.
How does the charging station know what the SOC is? Does the Bolt relay that info to the station, if so, how?
Thanks,
 

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The charging station simply supplies power. The rate of charge is controlled by the on-board circuitry in the Bolt.
 

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The charging station simply supplies power. The rate of charge is controlled by the on-board circuitry in the Bolt.
True for AC charging using an EVSE.

High voltage DC chargers rely on the car to communicate the desired rate of charge. The car uses Power Line Communication (PLC), sending data over the same wires used to deliver power. In other words, the Bolt does tell the DCFC at what rate to charge it.
 

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The charging station simply supplies power. The rate of charge is controlled by the on-board circuitry in the Bolt.
But doesn't said Bolt circuitry communicate with the station to tell it how much power? Unless I take the direct charge to literally. Thinking the wires are a direct connect to the battery through some simple relays at most.
 

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regardless of the actual communication - the logic/brains/control _IS_ the Bolt - the PowerStation is "dumb" - it provides power and the Bolt asks for a certain rate/current of power to be delivered - its under the car's control - that's the only way this works because temperature is also a factor - and only the Bolt/Battery know what the battery temperature is.
 

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regardless of the actual communication - the logic/brains/control _IS_ the Bolt - the PowerStation is "dumb" - it provides power and the Bolt asks for a certain rate/current of power to be delivered - its under the car's control - that's the only way this works because temperature is also a factor - and only the Bolt/Battery know what the battery temperature is.
This is in contradiction to itself. If the power station was dumb, it wouldn't make sense for the car to ask for a certain rate/current, as the power station would not know how to respond to such request.

I think we have to look at it this way:

- The car decides what needs to happen.
- The DCFC charger makes it happen.

Now, who is control? Who will say? :D

W.r.t. battery temperature: How difficult would it be for the Bolt to relay temperature information to the DCFC charge station? The screen on the DCFC station already shows battery SOC. Adding battery temperature would be rather trivial. I mean: I can see it on my phone, even wirelessly. I think the real problem would be that the DCFC station would have to know the various thresholds for all the different pluggable cars on the road.
 

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High voltage DC chargers rely on the car to communicate the desired rate of charge. The car uses Power Line Communication (PLC), sending data over the same wires used to deliver power. In other words, the Bolt does tell the DCFC at what rate to charge it.
I believe that the communications protocol runs over the pilot signal line. On an L2 "charger" (EVSE), the pilot line carries a PWM (pulse width modulation) signal that tells the car what maximum current it can draw. On a CCS connector it's a digital signal that allows bidirectional communication.

Part of the CCS protocol is an exchange of information between the car and the charger - the charger tells the car what it's maximum output is (volts and amps) and the car asks the charger to output a given DC voltage.

At the start of charging a relatively empty battery pack the car requests a voltage that's a fair bit higher than the pack voltage - the difference between the charger and pack voltages results in a flow of electricity (current, measured in amps) into the pack.

The car targets a certain power level (power in watts = volts X amps). As the pack fills, its voltage increases and the car continually adjusts the voltage requested from the charger to maintain a power curve that ramps power down as the pack fills in order to minimize wear on the battery cells.

But doesn't said Bolt circuitry communicate with the station to tell it how much power? Unless I take the direct charge to literally. Thinking the wires are a direct connect to the battery through some simple relays at most.
Yes, the car communicates with the charger as described above. The actual power wires from a DC fast charger are pretty much directly connected to the battery (through relays), bypassing the AC inverter that's used for L1 and L2 charging. But the pilot signal (a separate wire) lets the car control the DC voltage coming from the charger.
 

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A simple, ( but not exact) analogy is:

Think of your charging cellphone as "The Bolt", and a USB charging slot as the bolt's "Level 2 charger" ....

Modern fones ( with a max charge rate of 2.4 Amps), will plug into any / all various USB slots, regardless of weather the slot can supply a max of 300mA, or 500mA, 750mA, 1 Amp, 1.5 Amp, or 2, 2.1, 2.4A ect ..
The smart charge circuits in the fone (Bolt), know how to use the slots full power, taper it off, or shut it down as needed... The "charger" is actually in the fone...
When Bolt decides to use a L2 's "max" charge rate, it can "see" if its less than 32A ( say a 16A L2), & charge accordingly.. , just as a cellphone plugged into a 1A USB slot will charge slower than if in a 2A, The fone ( or car), can only "ask" for the "max" rate or percentage taper it down from that as needed, it can't "tell" the 16A charger for 150% of it's "max" ...
 

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the pilot signal (a separate wire) lets the car control the DC voltage coming from the charger.
There is not much easy info out there about CCS protocols. Do you have a source that explains this? From what I've read, communication is handled over the same 2 pins that feed power, which is why the protocol specifies PLC.
 

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There is not much easy info out there about CCS protocols. Do you have a source that explains this? From what I've read, communication is handled over the same 2 pins that feed power, which is why the protocol specifies PLC.
Yeah, CCS technical info is scarce without paying for the published standard. But I was able to find this:

http://tesla.o.auroraobjects.eu/Design_Guide_Combined_Charging_System_V3_1_1.pdf

...which shows a schematic of the connections and a timing diagram of the signalling sequence. This confirms that signalling is done over separate wires, which makes sense because you can't energize the power conductors without first getting the car and the charger to agree on what to do.
 

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which makes sense because you can't energize the power conductors without first getting the car and the charger to agree on what to do.
Um. No. The other info in your post was very useful, but an *intelligently designed* standard would not have that requirement. I am not saying that the CCS standard doesn't allow it - I am saying that they were f*cking insane if it doesn't allow it. Look at how fax machines work. They start communication at a very low baud rate, and exchange info about what each side can do, what speed is possible, and what definition (pixel density) they can agree on. That standard is from the late 1980s (well, it's been modified since, but ...). Any communication standard that FROM THE GET GO cannot have a basic starting position and agreed upon protocol for exchanging wants and needs is FLAWED. It's the 21st century, people.

But maybe I misunderstood your post.
 

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CCS communicates at 1Mb over the AC lines. The car sends things like VIN number, requested rate of charge. ~400vdc is sent over the DC plug pins. So... handshaking and signaling done over the AC pins, power delivered on the big DC pins.

L2 charging.... the EVSE equipment provides a pilot signal that uses the duty cycle of a waveform to indicate the max current the car may draw. The voltage of this DC waveform is used to communicate errors. The car uses a 2nd signaling pin to indicate back to the EVSE that the plug is in the charger socket and to get the EVSE to pull in a relay to put 120/220v on the AC pins. Handshaking and signaling done over a pair of 24vdc low voltage pins and power delivered on the AC pins.
 

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L2 charging.... the EVSE equipment provides a pilot signal that uses the duty cycle of a waveform to indicate the max current the car may draw. The voltage of this DC waveform is used to communicate errors. The car uses a 2nd signaling pin to indicate back to the EVSE that the plug is in the charger socket and to get the EVSE to pull in a relay to put 120/220v on the AC pins. Handshaking and signaling done over a pair of 24vdc low voltage pins and power delivered on the AC pins.
the pilot pin wave form is +/-12 volt, so wouldn't that make it AC? ? Voltage levels are used to signal status: no car present, car present, car present and ready to charge, car present and ready to charge but requires active cooling. IIRC no error conditions are communicated? The control pin is used by the car to detect a cable is plugged in (this is why the car stops charging as soon as you push the button on the car side plug). The evse uses the control pin to detect the capacity (amps) of the cable plugged in to the evse (for untethered stations).
 

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the pilot pin wave form is +/-12 volt, so wouldn't that make it AC? ? Voltage levels are used to signal status: no car present, car present, car present and ready to charge, car present and ready to charge but requires active cooling. IIRC no error conditions are communicated? The control pin is used by the car to detect a cable is plugged in (this is why the car stops charging as soon as you push the button on the car side plug). The evse uses the control pin to detect the capacity (amps) of the cable plugged in to the evse (for untethered stations).
There are two error states which can be conveyed on the pilot signal.


And the words I was looking for this morning were "control" and "pilot". I don't want to get so deep into this as to confuse anyone. In a /huge/ over simplification, Pilot signal communicates how much power the car may draw and control is a signal from the car to tell EVSE to pull in a relay to put 220v on the AC power pins. That way your dog doesn't get shocked chewing on your charger cable because there's no 220vac on that cable until the car is plugged in.

Yes, you are correct... +/-12v is AC... but not in this sense... it's low voltage DC used / co-opted for signalling. :) I'm always amazed at how much information can be put into one signal... Analog TV was the epitome.... horizontal sync, vertical sync, teletext, color and luminance info, and two or three channels of audio... all on one signal. The J1772 standard pales in comparison to the complexity!! :p
 

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Indeed, forgot about these two error states. Btw: state E can only occur by short cutting the pilot pin to ground. Most likely caused by a faulty cable. State F is not really defined, other than not being any of the other states. I have always assumed the evse sees both as an error without the car purposely sending them as an error.

The relay is engaged when the high side of the pilot square wave is pulled down to 6 or 3 volt by the car. The control pin has nothing to do with that. How do I know? My EVSE module does not have a wire attached to the CP terminal, yet it works just fine.
 

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Um. No. The other info in your post was very useful, but an *intelligently designed* standard would not have that requirement. I am not saying that the CCS standard doesn't allow it - I am saying that they were f*cking insane if it doesn't allow it. Look at how fax machines work...
I appreciate where you're coming from, and I have no doubt that it's technically feasible. But it seems to me that trying to use the same conductors for a low voltage control signal and 400 to 500V DC at hundreds of amps is asking for trouble. The last thing you'd want is some sort of fault in the charger to close the wrong relay and send 500V DC into the logic controller of your car. Better, I think, to keep those functions on separate circuits.
 

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Although this is about the type 2 based ccs, the first picture in this article may clarify matters. Low voltage signal pins are still there. As is the ground pin. But the AC pins are not there anymore.
 

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I appreciate where you're coming from, and I have no doubt that it's technically feasible. But it seems to me that trying to use the same conductors for a low voltage control signal and 400 to 500V DC at hundreds of amps is asking for trouble. The last thing you'd want is some sort of fault in the charger to close the wrong relay and send 500V DC into the logic controller of your car. Better, I think, to keep those functions on separate circuits.
I use a plug-in device to get ethernet to a non-WiFi device on the other side of my house. Sure, it's only about 10 Mb/s, but it transmits using the electrical wiring installed in the house - at WiFi speeds (well, 803.11b, slow, speed). There *should* be no problem using signals sent over the 400V lines. Any comm 'hiccup" would be just as possible using the low-voltage lines as the high-voltage ones.

Now that I think of it, I believe that CCS was designed to use similar comm protocols as std J1772, using the same pins, but using high-voltage DC for charging on new (different) pins. So my whole rant is ... off-base: CCS is a std meant to piggy-back off an older std.
 
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