90D "Not safe to drive," says Tesla: Battery overvoltage BMS_w098. Now what?

[Michael7S]

Our 90D (2015 Model S) shut down at the supercharger 200 miles from home with a list of errors. Tesla reps at mobile service and at the local service center said the car, "was not safe to drive" to tow it, and that the errors indicated that one of the cells was overvoltage.

Now I went through batterygate with my old P85, so I'm anticipating Tesla's lies and warranty avoidance tactics; "normal behavior, wear and tear, not technically part of the battery, customer fault", etc.

So to prepare for that, what are some of the objections you'd expect from Tesla service on what seems like a battery failure?

P.S. Both reps confirmed the errors did not indicate a 12v battery problem, or a loose frame cable. They both separately confirmed it was a cell overvoltage situation. I did get the car home and plan to do a battery scan before taking it in to service center. Just need to wait for the updated OBD connector to arrive in 'weeks.' Car is out of warranty, but still has 'months' on the battery/driveline warranty.

 

[beatle]

If it's a problem with a cell/module being overvolted, that's inside the battery. Seems pretty cut and dry that they will replace it. This is different from batterygate where the battery's capacity was just degraded; the car is completely inoperable this time.

 

[Michael7S]

Thanks @beatle, and agreed that seems sensible. But in theory, could the BMS cut out that entire section, reducing the battery capacity and thus rendering it 'within specs?' "The person who told you that wasn't qualified to interpret the code." "Oh the BMS is causing the overvoltage, so the repair isn't under warranty." Etc. etc.

Yeah, I dread this and admit I'm expecting the worst after dozens of fruitless service center nightmares from prior Teslas. I expect Tesla reps to have impenetrable defenses and avoidance systems, well-tested against thousands of owner complaints. Tesla will be well positioned to avoid any possible costs. Just trying to predict those and mitigate before the battles begin, e.g. scanning the battery beforehand, taking photos of the underside, etc.

 

[ucmndd]

But in theory, could the BMS cut out that entire section, reducing the battery capacity and thus rendering it 'within specs?'

No.

 

[MP3Mike]

With an overvoltage issues you have to be worried about the potential for the cell to overheat and catch fire. Though I thought I read that the BMS would go into a mode to drain the pack to try to prevent a thermal runaway event. (Though it could be a false overvoltage reading from a bad battery management board on a module.)

 

[Michael7S]

No.

Thanks. Well, let's hope I can report back some good news and that Tesla *actually* does the right thing.

 

[Michael7S]

Thanks. Well, let's hope I can report back some good news and that Tesla *actually* does the right thing.

Well one first good step. The estimate for today's service visit suggests that it is a $0 HV replacement based on the diagnostics. In the past they'd always try to charge me $200 even when doing warranty repairs. So a better start than the last dozen visits on prior cars. However it also estimates the car will be ready for pickup two hours after drop off. I'll share more as I learn.

 

[brkaus]

Well one first good step. The estimate for today's service visit suggests that it is a $0 HV replacement based on the diagnostics. In the past they'd always try to charge me $200 even when doing warranty repairs. So a better start than the last dozen visits on prior cars. However it also estimates the car will be ready for pickup two hours after drop off. I'll share more as I learn.

It's an "easy" swap if they have an appropriate pack in stock.

Hopefully they get it all sorted quickly and you get a proper fix.

 

[dmurphy]

It's an "easy" swap if they have an appropriate pack in stock.

Hopefully they get it all sorted quickly and you get a proper fix.

Bear in mind, in the "early" Model S days, there was an idea of swapping the pack as a recharge mechanism ... so to @brkaus' point -- it's a fairly easy thing for them to drop and replace the pack, provided they have one available. It was designed with that in mind.

 

[Michael7S]

Tesla just reported the repair as complete at 5:08am this morning. They were kind enough to put a 92% charge on the replacement battery.

However at 92% the 'range' is reported to be 234 miles.

The prior battery at 92% would report 254 miles 'range'.

This suggests that the replacement battery (even already degraded ~14.n%) is significantly lower capacity than the failed battery.

I've 'messaged' the same, politely, to the repair team. We'll see what happens.

 

[Zuikkis]

Sure they haven't just flipped the display from "ideal" to "typical"?

To my understanding 2015 S 90D had 270miles rated EPA range. 92% would be 248 miles.

234miles sounds right, 254 doesn't..

 

[Michael7S]

Good question.

The 90D is set at "rated" which is what I've used prior to the HV battery replacement. FWIW the manufacture date on the 90D is October 2015 but pre-facelift.

Consistently as we approached 100% SOC on trips, the rated range would display in the higher 260s - I recall seeing 268 miles several times because this also happened to be the peak rated 'range' of a '13 MSP85 I owned way back when, before it plummeted to 224 overnight with batterygate . I suspect if had we gone to 100% SOC the 90D would have shown range in the low 270s, but I can't claim to have seen it.

I'll be the first to admit that I'm ready for a fight with just about everything related to batteries when it comes to Tesla. They choked down my prior 85kWh battery to absurd capacity and charge rates and denied it all. They also installed a drive unit that had markedly less power/performance. They denied that too. We went round and round for years. A drunk driver t-boned the car at 60mph last year and that problem went away.

I just used SMT to see that the "Nominal Full Pack" is 74.6 kWh Not great, but not terrible. We'll see what happens with 'rated' range as we approach 100% SOC in the coming weeks.

 

[Michael7S]

Results: After a few complete battery cycles (same 160 mile drive we make often) the rated range tops out at 161. So while this appears to not be 'equal or better' than the battery replaced, it's pretty close. This is tempered with the HV battery failure happening days before the 8 year battery warranty expired. I mean how often does that happen? Usually it's a few days after.

So $0 for a replaced battery with a perceived loss of 8-15 miles of 'rated' range (which may change), vs. $6K-$20K out of pocket... I'm deciding to be OK with what I've ended up with.