2015 S (w/dual onboard chargers) no longer charging at full rate at home

[Hillshouse85D]

For 7.5 years, our dual charger equipped 2015 85D has charged flawlessly adding 62 miles/hour using a Tesla wall unit on a 100amp breaker. Until now, the car’s charger system has always accessed the full 80/80amps to deliver 62 miles of range per hour. For the last two weeks, the car’s charger has only been accessing approximately 60amps - adding about 47 miles of range per hour. I’ve tested the availability of the 80amps by switching on climate during charging to see the dashboard display change from 60/80amps to 80/80amps as long as climate operates.
I have done hard resets with no positive results. I have an upcoming service appointment, but it seems that the service center lacks any 100amp wall connector, taking the easiest display of the problem off the table. I have submitted logs and bug reports and hope for the best.
Any thoughts would be appreciated.

 

[Evee]

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[Hillshouse85D]

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[vcor]

Are there any warnings on the instrument cluster? I suspect not or you would have mentioned it. If there was a voltage sag, I could see the car reducing the current, but you should see a warning in the instrument cluster. If one of the chargers died, I'd expect you to be limited to 40 amps. Let us know what service finds out.

 

[beatle]

62A seems like a strange place for it to settle. When I've had my charging nerfed by a voltage drop on the house circuit, the car reduced current demand by 25% (40 to 30A in my case). An 18A reduction from 80A is a strange 22.5% reduction.

What if you set the max current to say, 50 or 60A, plug in and charge, and then try to gradually increase it back to 80 on the display? You can also watch the voltage during this time to see if it drops. When that happened to me, the session started at 230v and gradually dropped to 222v where it then cut the current to 30A. This let the voltage spring back up over 230v. The voltage doesn't have to sag much before the car will freak out and cut the current.

If you find your voltage dropping, I would check the connections at the HPWC and the breaker. Over time the terminals can loosen due to the heat cycles.

 

[Hillshouse85D]

Thank you vcor and beatle for your replies and suggestions.
This 3 week old sporadic phenomenon has not been accompanied with any error messages or instrument display messages.
I have a collection of photos (perhaps a dozen)with the amps in the 57-62 range. Voltage usually is steady showing 243. I wondered if my wall unit or 400amp panel could be part of the problem, but turning on climate during these episodes moves the dashboard displayed amps right up to 80/80 every time. Turning the climate off triggers a drop in the amps, returning to the 60ish range. This seemingly suggests to me that the problem is with an onboard component or system.
I am supposed to pick up m car tomorrow. I’m not optimistic. I provided a series of dates and times for review of the log and was actually led to believe that a review of the log showed an issue. I fear I’ve been misled.
I will report my experience and any findings. I welcome your continued thoughts and suggestions. Thank you.

 

[beatle]

The dashboard display of amps shows what the car is drawing from the wall, not necessarily what's going into the battery. It sounds like the car is reserving some of its charging capacity for climate control even when the climate control is not operating. The resistive heating element can draw up to 6kw, but 62 of 80 amps only leaves 18A on the table, and @ 240v that's only good for a little more than 4kw. I'm not sure what the AC compressor draws. Without a fault, this sounds more like a software glitch of the car thinking some component of the HVAC system is still on even when it's not.

If you have a bluwtooth OBD2 dongle and a diagnostic cable you can get better intel as to where the car's power is going.

 

[Hillshouse85D]

Sorry for my delay responding. I picked my car up Monday morning and, by mutual agreement, returned the car for additional diagnostics on Tuesday afternoon. This afternoon I picked the car up and was informed that service technicians had found that the battery coolant heater was failing. Although my car is always garaged, the weather on the SF peninsula has been cool. Bottom line- I’m hoping that the Tesla techs have correctly identified and corrected the problem.

I have a Tesla 4-year extended warranty that I paid dearly for that will expire in June. This is the first time I’ve ever used it. If anything is going to fall, I would like it to happen during the next five months.

Thank you for your time and thoughts. I will hop back onto this thread if this fix does not work. Beatle, thank you for the OBD2 dongle/cable suggestion. I don’t own one but have seen them referred to in other conversations.