Understanding 85kWh battery limits

[kirkusss]

Happy new year, Everyone!
Opened a new request with all the data and got an answer from the owner’s manual…basically telling me the car can limit power for many reasons, but nothing specific to my case.
At this point, every time I leave the car parked under 30% for few hours it will get power limit that won’t disappear until charging. SC asked if this started after a SW update and closed the service request right after…

 

[aerodyne]

Happy new year, Everyone!
Opened a new request with all the data and got an answer from the owner’s manual…basically telling me the car can limit power for many reasons, but nothing specific to my case.
At this point, every time I leave the car parked under 30% for few hours it will get power limit that won’t disappear until charging. SC asked if this started after a SW update and closed the service request right after…

Keep up the pressure on the SvC. I see you have HV data showing on the IC, I have never seen that before. Was this enabled by the MCU2 upgrade?

If you have the new update, and MCU2, you should have Service Mode and be able to do a battery health test. I know that degradation is not covered by warranty, but high degradation might be a tell that something is wrong.

Since you have SMT:
What cell voltage delta are you seeing at rest? Do you have a string that is consistently low? Can you see if the 4 coolant pumps are running at 100% below 73% SoC?

I'd you can make another trip to the SvC, ask them to open Toolbox and show you the CAC on each module. They won't let you take a picture probably, but you can write them down. Then see if any of the values are out of spec per the service manual, or ask Jason his opinion.

If I still has my 85D, I'd be all over the 057 warranty and pack replacement options.

I'm really hoping Tesla does right by you, but afraid it won't be easy.

 

[kirkusss]

The menu is now gone, was a leftover from MCU1 root. Gone when I pressed by mistake the right wheel. Well, SMT to the rescue.
I have no battery test in Service menu and not sure if legacy S should have it.
At rest the imbalance seems very low, between 6 and 10mV most of the time, with over 200mV with load.
The pumps are at 100% under load, at idle they are at low 10-25% or stopped.
I am thinking at the 057 warranty to get the proper readings from their device.

 

[wk057]

Very likely just temp related limits. 20C at < 25% SoC will still give power limits, for example. If you have normal power at 80%+ SoC at 20-25C temps, then you're fine. The active heating profiles have been tweaked a lot over the years, and are geared towards efficiency vs power at lower SoC. Unless you're sagging to < 260V under WoT, you're not actually limited by any physical limitation with cells and likely just a cautious BMS thermal+SoC based power limit. Any time regen is limited < 50% SoC, it's also almost always a thermal related limit. It could be a single temp probe throwing things off, since the temp reported in the diag panel on the IC is an average, but the BMS has to go with whatever is worst case.

"Uncorking" raises some of these limits, if that's an option.

 

[kirkusss]

@wk057 thank you for the insight on the profile tweaks.
While the regen limits based on temps are not a concern as they go as the battery heats up, the power limit won't go away. Had it come at 29% and battery over 20 Celsius and did not go away even when the battery went up to 30 degrees. The only way to get rid of it is charging. This was not the case few months back when the battery temps were the same.
And yes, I get sag to 250V under WOT starting ~40% SoC

 

[kirkusss]

@aerodyne , @wk057 what is an acceptable CAC imbalance? Did some comps with my friend's P90D and while his pack had same voltage drops (but no power limits), his CAC imbalance was at 4.2Ah on SMT, compared to my 2.5Ah

 

[aerodyne]

@aerodyne , @wk057 what is an acceptable CAC imbalance? Did some comps with my friend's P90D and while his pack had same voltage drops (but no power limits), his CAC imbalance was at 4.2Ah on SMT, compared to my 2.5Ah

I don't know, but I recall that when viewing on the Tesla toolbox, unacceptable values are highlighted in red or green.

Very rough numbers...Assuming a capacity of 3000 mAH per cell, and 72 cells per string, then you numbers sound pretty high, 10-20 %. If your numbers are at the module level, then 1/6 of that.

 

[kirkusss]

Based on the numbers of 212-214Ah it seems to be per group of 74 cells, so only 1-2% variation

 

[Wim_V]

@aerodyne , @wk057 what is an acceptable CAC imbalance? Did some comps with my friend's P90D and while his pack had same voltage drops (but no power limits), his CAC imbalance was at 4.2Ah on SMT, compared to my 2.5Ah

Is SMT able to read the CAC per brick?

 

[aerodyne]

Is SMT able to read the CAC per brick?

Not as far as I am aware.

 

[Doanster1]

@kirkusss I’m fairly certain this is due to recent software updates. I noticed and experienced the exact same thing as you. Power limits kick in at <30% SoC and battery not up to temp/regen limited. Kicks in a little later if full regen available. They really want to protect our precious P85Ds.

A few weeks ago during a cold snap, I came out to the car and it reported I had GAINED 3% SoC. Strange…

 

[kirkusss]

That’s interesting. Wonder if this trigger is only for certain cars or it’s a fleet update for all 85s.

 

[Doanster1]

That’s interesting. Wonder if this trigger is only for certain cars or it’s a fleet update for all 85s.

Not sure, but def recent event because power limits never kicked in until very low SoC.

 

[Doanster1]

Did a little experiment. I knew the car was at ~25% SoC the other night. The next morning, I pre-heated the car via the app (yes, the bacon strips appeared!) before the first drive of the day. When I departed, full regen was avail and there were no power limits. The limits didn’t kick in until 12% SoC, which is the normal behavior.

 

[kirkusss]

Tried as well some other scenarios and driving without any WOT does not trigger any power limit below 30% (unless pushed).
Will test the car next month from Montreal to South Florida. If it doesn’t break with all Supercharger stops she’s a keeper. Was looking to jump into a newer one, but would be at least 20k canadian dollars and would loose FUSC and MCU2. If battery fails outside warranty would pay the around the same to get probably the 350V and still keep FUSC and have higher charging speeds.
Of course, @wk057 warranty plan is also in the books

 

[kirkusss]

Just finished a 6000 km trip from -20 degrees celsius to +30 and back.
Had 28 supercharging stops for a total of almost 1000kWh and few hotel AC charges for around 190kWh.
Supercharging is slow, especially after 30%, had to go deep and manually select V3 superchargers. The navigation always aimed at over 20% arrival SOC at V2 that were more than half full.
No wait times on any stops from Montreal to Miami and back. Only noticed that driver side louver is not working, had an AC reduced power mesage twice.
Would definitely enjoy a faster supercharging than a free one, but the 85 pack worked without any issues and the max I have pulled out of it was 67kWh in one leg.
Now doing the math between the 90kWh pack and jumping on a model Y. Or just wait for the pack to fail and play the refurb pack lottety.

 

[kirkusss]

As I am days before the end of the warranty I remembered I had a small borescope from my BMW timing chain days. Then it helped replace it 800 before the end of the extended warranty.
Now it helped check the fuse cover. My car has the AC drain relocated, but seems a lot of moisture/dirt is present in the area, especially in front of the car.
My apologies to @wk057 and @Recell for tagging you, how bad does it look?
For the pics quality, did I mention the borescope was also cheap?
Thanks for checking!

Took also a video:

 

[wk057]

Not the worst I've seen. Not great though. I'd be more concerned about what the bolts immediately behind the front hump near the spine look like after seeing that. If water gets in the fuse holder it's annoying but sometimes fixable. If it gets through the spine or into a module chamber, then it's game over.

 

[kirkusss]

Thank you. Will definitely check Tomorrow behind the hump, hope to have enough clearance. Should I report this find to Tesla being so close to the warranty end?

 

[wk057]

Thank you. Will definitely check Tomorrow behind the hump, hope to have enough clearance. Should I report this find to Tesla being so close to the warranty end?

You can try, but I doubt they'll do anything unless there's an isolation issue.