CanadianBear
Member
I'm having some issues with L1/L2 charging, and was researching the topic in the last few weeks, so decided to share with the community.
I have a 2018 SL 40kWh 60k since not too long, great car, not perfect, but overall quite good. Was charging L2 around the city, until it stopped accepting charge few weeks ago. L3 works fine.
Brought it to the local EV shop, who diagnosed that PDM needs replacement. No sh* Sherlock, let's just buy a new car altogether. While I wait for the right used PDM to pop up, decided to research the topic myself. The car attempts to start charging, 1st or 2nd blue light starts blinking (depending on the SOC at the time), battery connectors underneath the car clink, EVSE clinks, and then nothing happen for exactly 1m50sec, when the whole thing disconnects and go dark. No power drawn.
This tells me that the proximity pilot works, and the control pilot does not. I don't have the actual DTCs to support it, but I don't think the diagnostic is that good anyway to pinpoint the exact failing component.
As I understand the J1772 protocol, once the proximity is confirmed, the protocol has another three-step security protocol, ensured by the diode, 2.7kOhm resistor and 1.3kOhm resistor (abundantly explained on OpenEVSE and elsewhere). Looks like older Leafs had at least some of these steps (like the diode check) performed on the circuit board in the PDM, which was a bit naive, but early days anyway. I was looking in particular at the 296b1-5sa0a harness assembly that runs from the J1772 female socket (on the car) to the PDM. Without disassembling it myself (I'm driving the car daily), and looking through the PDM teardowns and pictures of harnesses for sale, I come to quite strong conclusion that only three wires enter the PDM from the 296b1-5sa0a harness: hot, neutral and ground (on the exterior).
Logically then, the J1772 three-step handshake (12v down to 9v down to 6v part) is occurring somewhere outside of the PDM. It happens either in the black boot on the inside part of J1772 port, or via the black wire that goes from the main L1/L2 harness within 40cm or so from the inside of the port.
Before I start tearing down the port, was wondering if someone has tried it already and has come to a different answer. Basically, replacing the PDM feels like a lazy solution because the L1/L2 port harness connects to the inside of the PDM, and both are most likely sold together as one piece. It would be funny if many PDMs got replaced because of a bad J1772 protocol handshake, that occurs completely outside of the PDM.
Thanks for your thoughts.
I have a 2018 SL 40kWh 60k since not too long, great car, not perfect, but overall quite good. Was charging L2 around the city, until it stopped accepting charge few weeks ago. L3 works fine.
Brought it to the local EV shop, who diagnosed that PDM needs replacement. No sh* Sherlock, let's just buy a new car altogether. While I wait for the right used PDM to pop up, decided to research the topic myself. The car attempts to start charging, 1st or 2nd blue light starts blinking (depending on the SOC at the time), battery connectors underneath the car clink, EVSE clinks, and then nothing happen for exactly 1m50sec, when the whole thing disconnects and go dark. No power drawn.
This tells me that the proximity pilot works, and the control pilot does not. I don't have the actual DTCs to support it, but I don't think the diagnostic is that good anyway to pinpoint the exact failing component.
As I understand the J1772 protocol, once the proximity is confirmed, the protocol has another three-step security protocol, ensured by the diode, 2.7kOhm resistor and 1.3kOhm resistor (abundantly explained on OpenEVSE and elsewhere). Looks like older Leafs had at least some of these steps (like the diode check) performed on the circuit board in the PDM, which was a bit naive, but early days anyway. I was looking in particular at the 296b1-5sa0a harness assembly that runs from the J1772 female socket (on the car) to the PDM. Without disassembling it myself (I'm driving the car daily), and looking through the PDM teardowns and pictures of harnesses for sale, I come to quite strong conclusion that only three wires enter the PDM from the 296b1-5sa0a harness: hot, neutral and ground (on the exterior).
Logically then, the J1772 three-step handshake (12v down to 9v down to 6v part) is occurring somewhere outside of the PDM. It happens either in the black boot on the inside part of J1772 port, or via the black wire that goes from the main L1/L2 harness within 40cm or so from the inside of the port.
Before I start tearing down the port, was wondering if someone has tried it already and has come to a different answer. Basically, replacing the PDM feels like a lazy solution because the L1/L2 port harness connects to the inside of the PDM, and both are most likely sold together as one piece. It would be funny if many PDMs got replaced because of a bad J1772 protocol handshake, that occurs completely outside of the PDM.
Thanks for your thoughts.
