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Battery recalibration

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lzolman

Never thought I'd be driving the world's best car!
Supporting Member
Jun 13, 2019
547
1,395
Boston North Shore
I ask this question w/r/t my '21 MSLR, but I'm also planning to apply answers to our '18 M3. Please let me know if there is any reason to treat them differently.

Lately in my MSLR, even though I charge only to 90-92%, I've been getting the "regen limited" notification. I used to get that only when I charged up near 100%. So, I take this to mean the battery charge level calibration is now off.

I asked about this at the Service Center a couple days ago when picking Nameless up from service, and the guy told me that the advice they are currently giving is this:

Run the battery down as low as possible, then charge to 100% with the 110V charging cable. Do this 4-5 times (!!!!!). Pressing him a bit, he said the key was to charge SLOWLY, but I'm hoping it doesn't actually have to be THAT slow to be effective, because that process would take me a month LOL.

It just so happens I won't be needing the car much this week, so I'm running it down now in the garage (in Boston, it's 30 degrees, so I opened the windows and told the climate control to keep it at 77). When it gets down near 0 I'll start the process with the 110V charger and I'm pretty sure I can get it up to 100% by next weekend.

So my questions: what are your experiences with attempting to recalibrate the battery, and did you have to jump through this extreme set of hoops?
Would the lowest L2 setting be a reasonable substitute for using the 110V charger?

Thanks!
 
From what i have read in this form is that you need to put the car in deep sleep mode at different SoC levels ( start at lower SoC levels and then do it at higher SoC levels in stages) . It seems this allows the BMS to re-calibrate the battery gradually and make it more current to the real battery status.
 
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The correlation you’re making between limited regeneration and battery calibration doesn’t really pass the sniff test.

1) it’s not at all uncommon to have limited regen at 90% or above. Especially when it’s cold, which I imagine it is this time of year in Boston.

2) The full charge cycle on 120v to calibrate sounds like full-on junk science. It’s not going to do much of anything to “calibrate” your battery and certainly isn’t going to do anything at all to address your regen observation.

The battery is very good at taking care of itself without all this sorcery.
 
OK, thanks for the "limited regen" feedback, I'd just never seen it do that before (including through all of last winter).
The "sorcery", BTW, isn't about trying to give the battery more range, just about having it report the battery's actual range.

And rice&curry, I'll add some deep sleep time to the recharge regimen, thanks.

One other thing the service rep said was that most of a new battery's range (actual, not just reported) that gets lost is lost within the first two years, and then they stabilize. Does that match the reality you guys have seen?
 
Does the Refresh S have the Energy widget available to view on the Instrument Cluster (it's available on the "Legacy" S at least)? If so, you can see the amount of regen limited by dashed orange lines on the regen side of the widget.

I'm probably not a good source of information about your battery range loss question as I bought mine when it was 3.5 years old already.
 
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Actually I'm pretty unfamiliar with the widget, as they just arrived on the refresh S a short while ago. I forget it's even there. I'll check it out!

Well, I just learned something and I feel like an idiot (actually not an uncommon occurrence.) I used to think the amp slider had no effect when you're connected to 110V, and I never adjusted it. I was faked out by the numbers, they looked way too high for the amount of current being drawn at 110. And just now it hit me: an amp isn't the same at 110 than 220. Duh. So those (few) times I charged at 110 I've been getting 2/3 mph, and with the slider all the way to 12A I'm actually getting 4mph, which means this won't take as long as I thought it would.

Coulda been worse... I might not have realized this until AFTER spending 10 days to charge up at 110V LOLLLLL!
 
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One other thing the service rep said was that most of a new battery's range (actual, not just reported) that gets lost is lost within the first two years, and then they stabilize. Does that match the reality you guys have seen?
Yep, that's expected. While it varies a bit based on usage too, a rough estimate is losing 2% capacity the first year (12,000 miles) and about 1% a year thereafter. There are other factors, but really not worth worrying about. Keep in mind the range indicator is an estimate. There is no way to measure the exact chemical state of the battery, outside of fully charged and fully discharged. That said, Tesla does a fairly good job of estimating the range - just don't assume it's perfect.
 
I ask this question w/r/t my '21 MSLR, but I'm also planning to apply answers to our '18 M3. Please let me know if there is any reason to treat them differently.

Lately in my MSLR, even though I charge only to 90-92%, I've been getting the "regen limited" notification. I used to get that only when I charged up near 100%. So, I take this to mean the battery charge level calibration is now off.

I asked about this at the Service Center a couple days ago when picking Nameless up from service, and the guy told me that the advice they are currently giving is this:

Run the battery down as low as possible, then charge to 100% with the 110V charging cable. Do this 4-5 times (!!!!!). Pressing him a bit, he said the key was to charge SLOWLY, but I'm hoping it doesn't actually have to be THAT slow to be effective, because that process would take me a month LOL.

It just so happens I won't be needing the car much this week, so I'm running it down now in the garage (in Boston, it's 30 degrees, so I opened the windows and told the climate control to keep it at 77). When it gets down near 0 I'll start the process with the 110V charger and I'm pretty sure I can get it up to 100% by next weekend.

So my questions: what are your experiences with attempting to recalibrate the battery, and did you have to jump through this extreme set of hoops?
Would the lowest L2 setting be a reasonable substitute for using the 110V charger?

Thanks!
Well, it´s cold in Boston now right?
 
I think it is more like 4-5% in the first year and then 1% after that. A lot of ranges are above what they are supposed to be early on so people tend to neglect that. But I am sure that 2% happens, I just think the average first year loss is greater than that.
I have a 240 original range car that is 218 or so now. It came with 246 and by memory it was down to 232 after the first year. So do you call that 8 miles lost or 14 miles lost which is roughly 3% or 5%?
It then lost about 2 per year which is really easy math.

Agree that slow charging balancing is BS. I have done what you are proposing less than 5 times in almost 8 years. Mostly at vacation home rentals but I don't think I ever got to full battery - but I did sit at 120V for a few days - with some intermittent driving.

Just take it down to 10% and back to 100% once or twice - maybe not by supercharging. The service center recommended technique is probably for worst case scenario situations. Kind of like when they tell you to shut off the router for 5 mins when about 45 sec will do it. Also agree that regen limiting is not a balance issue. I would not spend all of your time near 90% unless you really need it. I realize there are varying viewpoints on this, but physics says this is not ideal from a battery standpoint.

Also, software updates can change behavior of the car. The regen has become gradually more limited in the cold over several years with software updates. I would not be surprised if the same thing has happened to the newer cars. Again physics doesn't change - sometimes tech people think they have learned to overcome it but .... physics.

Tesla has become more sensitive to the battery regen limiting and how other cars don't do that. Hence, the new mode which simulates regen with brakes. I would not be surprised if the notifications are more apparent than prior. Like you had limited regen last year, the car just didn't make you aware of it.

The pitfalls of too frequent, poorly documented software updates in a car that people aren't used to
 
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I don't think you should be charging to 100% frequently due to the limited regeneration message...90% maximum normally is best. Tesla told me this and just to let the BMS system handle it. May be you can try charging to 100% once with a level 2 (240 V charging connector) and drive it within 30 minutes after the charge completes to get it closer to 90%. May be also try to get a second opinion at a different service center as it's possible someone at the one you went to could have been misinformed.
 
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Sounds like your limited regen message is coming from cold weather at 90%. No surprises there.
Regarding "calibrating" your SOC. Based on mine and @WilliamG experience with our 1st Plaid HV battery packs that ended up being replaced. The way you "calibrate" is let the car sit at a 90% SOC for 72 hours and let the car "sleep". Do not open the app, or have any data monitoring apps active.
Based on our experience, this information turned out to be correct. Any missing SOC tended to reappear after doing said calibration.
The "old" method of discharge to a low SOC and recharge to a high SOC a few times is no longer a thing according to Tesla Service.
 
Thanks everyone. I've been teaching a class all this week (over Zoom, sitting on my a$$ at home) so I've been letting Nameless charge up at 4mph on 110V. I guess now I know my next attempt will be to let it sit at 90% for 3 days.

But right now something weird is happening, wondering if anyone can explain: I've been at 382 miles for about 3 hours at least (may have been longer before that), charging at 4mph, and the entire time it has been saying "30 minutes remaining".

I'm getting a bit uncomfortable just letting it keep charging, as I don't know what's going on...
 
TL, I realize I'm fortunate to have that many miles. The specs said 405 when new, but then all of a sudden new ones became spec-ed at 395, so I suspect mine became 395 as well due to software changes. If I real ly have 382 (I know, everything is relative, so not really 382, but then, 395 wasn't really 395) that's only a loss of 13 miles out of 395 and I'm happy.

This is about the "right" range for me, I'd be frustrated with less on my long road trips (coast-to-coast in May, and Boston <--> Sturgis in August for motorcycle week plus another motorcycle trip to Ohio--bike transported separately) and don't need more. Life is good.
 
Thanks everyone. I've been teaching a class all this week (over Zoom, sitting on my a$$ at home) so I've been letting Nameless charge up at 4mph on 110V. I guess now I know my next attempt will be to let it sit at 90% for 3 days.

But right now something weird is happening, wondering if anyone can explain: I've been at 382 miles for about 3 hours at least (may have been longer before that), charging at 4mph, and the entire time it has been saying "30 minutes remaining".

I'm getting a bit uncomfortable just letting it keep charging, as I don't know what's going on...
The period that it was "30 mins remaining" it was "balancing cells"

Again, don't worry too much about it and drive it set to % not miles. You will get hung up on the number. When it's set for percentage, it wont bother you.
 
Sounds like your limited regen message is coming from cold weather at 90%. No surprises there.
Regarding "calibrating" your SOC. Based on mine and @WilliamG experience with our 1st Plaid HV battery packs that ended up being replaced. The way you "calibrate" is let the car sit at a 90% SOC for 72 hours and let the car "sleep". Do not open the app, or have any data monitoring apps active.
Based on our experience, this information turned out to be correct. Any missing SOC tended to reappear after doing said calibration.
The "old" method of discharge to a low SOC and recharge to a high SOC a few times is no longer a thing according to Tesla Service.
Sounds like your limited regen message is coming from cold weather at 90%. No surprises there.
Regarding "calibrating" your SOC. Based on mine and @WilliamG experience with our 1st Plaid HV battery packs that ended up being replaced. The way you "calibrate" is let the car sit at a 90% SOC for 72 hours and let the car "sleep". Do not open the app, or have any data monitoring apps active.
Based on our experience, this information turned out to be correct. Any missing SOC tended to reappear after doing said calibration.
The "old" method of discharge to a low SOC and recharge to a high SOC a few times is no longer a thing according to Tesla Service.
Interesting! where can I see the original thread?
 
It's a pretty lengthy thread, I found the beginnings of it I believe here:
 
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