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Range Loss Over Time, What Can Be Expected, Efficiency, How to Maintain Battery Health
- Thread starter KK_RedM3
- Start date
AlanSubie4Life
Efficiency Obsessed Member
I was at Yosemite a year ago, drove in 70-100 degree temperatures on the way there, parked my car overnight at Tuolumne Meadows at ~40 degrees, and it gained 1-2%. (I took pictures because I was curious, so I am certain of this.)
So you’ll find the ups and downs don’t necessarily follow a pattern of high temp parking - increase, vs. low temp parking - decrease. Thought certainly that could make it more likely to see an increase or decrease.
All of these fancy new features almost make me want to bail out of the FSD Beta program. Almost.
I have observed this fluctuation in the summer and the fall when temperature was fairly steady. Temperature might have some effect, but I'm thinking this is unrelated, because sometimes it takes just a few minutes to see the gap.
I'm glad to find out that it is common and it is not just my car though.
Nope, parked. I think I had the HVAC off as well, but will check again next time I'm at a higher SOC.
If you just parked maybe the Voltagedelta hadn’t hade the time to flatten after the drive.
18mV seems high anyway, maybe charge to 90% or slightly above to letvit balance itself.
I almost always see 4mV if not at very low SOC or very high before the balancing is done.
Currently sitting at 80% and seeing 10 mV of imbalance. Going to charge to 90% overnight and check in the morning.
The 18 mV reading was a bit sporadic, but 12 mV was easy to see. Would be nice to be able to tell which balancing circuits are on...
The balancing is commenced when the SOC is about 90% or more. I think the logic for balancing is set to a specific cell voltage, but > 90% displayed does the trick.
I dont understand your sentence about which balancing circuits?
Tesla burn of voltage from the ”high” cells via resistors. I also think I did read that the logic had ”if imbalance > 5 mV
I would not think there is another balancing than burn of resistors with the logic ”at least 4.XX V/cell” and ”only if imbalance is 5 mV or more”.
AlanSubie4Life
Efficiency Obsessed Member
Right - what I mean is that it would be nice to know when the car was actively bleeding off energy from cells that have been determined to have drifted above the other cells.
Other people with more knowledge of the inner workings of the BMS have stated that the BMS can start balancing at almost any time. And because the balance resistors are so small, it takes quite a bit of time for any balancing to occur. I have heard some rumors that the BMS may not initiate balancing until SOC is over a certain threshold (90%? 93?), but I'm not sure how reliable that information is.
So it would be nice to know when they are activated for a particular cell-group - I would not be surprised if it was in the CAN data, but just hasn't been identified. If nothing else, so we could figure out when balancing is triggered, at least.
Late 2021 LR MIC w/LG 75kWh range update
October showed 532km @ 100%, a gap down from 537km in September (and steps down to 531km immediately when put in D and rolling, so going with that number.)
Since last time to full the car has been spending some time at higher charge levels, including two nights at 90-92% to allow for more diverse BMS readings, and cell balancing/ bleeding.
With a possible 550km max EPA range for this configuration - 19km = less than 3.5% loss for the first year.
Happy with the car.*
*Minus the auto high beams on Autopilot situation. Does not belong in the battery forum but I hope it is discussed elsewhere and is brought to attention. It needs fixing, fast, as for most us it is only going to get darker in the next months. Other cars dim lights correctly.
Yes, you can push forward on the stalk to cancel it, but come on.
October showed 532km @ 100%, a gap down from 537km in September (and steps down to 531km immediately when put in D and rolling, so going with that number.)
Since last time to full the car has been spending some time at higher charge levels, including two nights at 90-92% to allow for more diverse BMS readings, and cell balancing/ bleeding.
With a possible 550km max EPA range for this configuration - 19km = less than 3.5% loss for the first year.
Happy with the car.*
*Minus the auto high beams on Autopilot situation. Does not belong in the battery forum but I hope it is discussed elsewhere and is brought to attention. It needs fixing, fast, as for most us it is only going to get darker in the next months. Other cars dim lights correctly.
Yes, you can push forward on the stalk to cancel it, but come on.
While I havent checked the increased balancing range, increasing the range for calibration would increase the energy consumption.
Besides that, as long as we have normal imbalance there is no real reason to regularly balance the battery at lower SOC’s. The exception would be if the imbalance exeeds a limit and is abnormally high at other SOC’s which would be an exception and not happening regularly.
Balancing actually only move the SOC of individual cells so the individual voltage match better at that certain SOC / Voltage.
If we balance to perfect balance at 70% SOC, it will not be perfect when reaching 40-50%.
Balancing is mostly needed to reach full capacity in the battery at 100% SOC. Otherwise the capacity would not be reached if many cells is low when the first cells reach 100%.
If the car is used (sleeping) often at a certain SOC the cell voltage tends to stay quite close.
I will not say that I do not believe wk057 but i do not really see the win in balancing cells regularly at lower SOC.
I see mostly 4mV shortly after any drive after using 55% charging target and when I grab the car ling afterwards, it still is 4mV so no balancing has taken place.
I did a test about 1 1/2 year ago, that would probably be before any software change.
Having 4mV after a 55% charge, I charge to 60% waited/checked, charged to 70% waited/checked, etc up to 90%.
My car had 4 mV after charge each time, both immediately and 1-2h hours after except at 90% (I think 92% was reached) when it was 5mV ( I think) which then was 2mV after 1-2 hours.
Model 3 has higher resistance in the balancing circuits than Model S and X.
3 need longer time to balance due to that.
I think the balancing logic normally was set to:
-At least 4.XX V/cell (about 90% displayed)
-At least 5mV imbalance.
There would not be any reason to start balancing every now and then at low SOC for the BMS.
Candleflame
Active Member
PianoAl
Active Member
I wonder if discussion of good battery charging hygiene makes people more alarmed when they see range loss. Like, "Hey, I never charged over 80%, so is something wrong?" Calendar degradation is a thing.
Though it may be different for LFP batteries (that a new Model 3 with 272 miles of rated range in the US has) versus NCA batteries.
PianoAl
Active Member
My understanding: LFPs also don't love 100%, but they need it to calibrate the BMS, and they last longer in general.
PianoAl
Active Member
Excellent info, thanks.
Here's my takeaway from that graph:
After 9 months, you'll see the same degradation whether the car's at 80, 90, or 100% SOC. You'll see significantly less degradation if SOC is 70% or below.
Here's my takeaway from that graph:
After 9 months, you'll see the same degradation whether the car's at 80, 90, or 100% SOC. You'll see significantly less degradation if SOC is 70% or below.
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