lightningltd
Member
As far as I remember, there is a warning on rechargeable batteries that says that overcharging can overheat batteries. Also, the extra cooling could be discharging them for testing module voltage variations.
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Wiki Sudden Loss Of Range With 2019.16.x Software
- Thread starter Dutchmeeuw
- Start date
My understanding too.
Yes to this also.
Hence my thought that it could be some edge condition that isn't picked up by BMS but allows some sort of runaway condition to take hold within a brick where there is less control.
A high resistance cell would get hot when current flows through it. Does anyone recall / know the value of those fuses?
aerodyne
2 of 3 EV's - Defect Free!
This is worth exploring. I am going to take some time to reread the first post on this thread.
Meanwhile, IIRC; 85 pack has:
16 modules
6 strings per module
74, 18650 type cells per string
7104 cells total.
6 x 16= 96, if these are in series at 4.2 VPC, then 96 x 4.2. = 403 volts.
aerodyne
2 of 3 EV's - Defect Free!
Sometimes a visual helps. From SMT just now...note my "Problem child" module 2. Still get good range/nom capacity north of 260RM/75Kwh after a drive.

Think about what's going on in your brick 2. Although all the cells are strapped in parallel, the internal condition of the cells might not be (probably isn't) identical. Yet they are all forced to the same voltage by virtue of them being in parallel. As long as the cells are well matched and in good shape then there is no problem. If a bunch are high resistance then less current flows through them during charging than through the good condition, lower internal resistance cells. Those cells presumably take on less charge and also get hotter during charging. As they warm up, their internal resistance could drop, somehow extending the internal current flows between stronger and weaker cells in the brick.
If too much current flows through one cell, it drops from the brick, but what if the internal condition of many cells are evenly mismatched? How much heat could be generated within that one brick and how well could that heat be dissipated by the cooling system?
This is all conjecture. But I feel like if it is NOT dendrites, then it is some other heating effect that takes place within bricks where it is less possible to observe / control.
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aerodyne
2 of 3 EV's - Defect Free!
aerodyne
2 of 3 EV's - Defect Free!
But Tesla said it was!
After the Hong Kong fire incident in May of 2019, Tesla said this:
“As we continue our investigation of the root cause, out of an abundance of caution, we are revising charge and thermal management settings on Model S and Model X vehicles via an over-the-air software update that will begin rolling out today, to help further protect the battery and improve battery longevity.”
Tesla is updating its battery software following a car fire, claims improve longevity - Electrek
Your interpretation of what Tesla said. Nothing in what Tesla said indicated that the changes were to prevent fires. They hadn't completed their investigation so they didn't, and may still not, know what caused the fire.
No. It's not what caused the fire. It about why the update was issued for. Based on what Tesla said at the time, it was their reaction to the multiple fire incidents. @wk057 said the "the range loss/charge speed loss issue isn't related to fires." That is in contradiction with the stated reason by Tesla on why the update was issued.
Agreed.
But by the timing and wording of Tesla's press release, it does appear to link their actions regarding battery management to their investigation of the fire. Over a year later, have their investigations delivered any more detailed info.?
And wouldn't you think that by now, if there was no issue that the 'abundance of caution' was needed for, Tesla would have reverted charging and battery capacity back to the correct settings as per when the vehicles were sold?
I don't see how you can read it as an over abundance of caution in response to fires...... Nothing to do with fires...... We will continue to be overly cautious regarding a non existent risk - and over a year later have nothing further to add.
No no no floor is open. Think hands are becoming fist soon. So be careful.
I would try to charge at very low current for long time. I am not sure what the minimum setting is. The BMS might be able to bring that cell group in module 2 up to normal voltage.
I agree that this approach would seem the best change to bring lazy bricks back in line.
Nothing to do with max and min SOC, but purely so that the battery remains on charge for a prolonged period at a low rate, charge from say 30% to 80% at lowest rate poss, like 1.5kw.
aerodyne
2 of 3 EV's - Defect Free!
Something to think about....
Tesla is continuing to replace 85 battery packs that fail under warranty, with refurbished packs.
If there was truly some sort of defect in the pack and cell design, why would they do this, and risk more bad press, aka, "Rebuilt Tesla battery explodes on way home from service center" instead of replacing them with new packs?
It is conceivable charge/battery/regengate were done out of an abundance of caution, but also has the effect of reducing warranty claims, so no reason to roll back the changes.
Tesla is continuing to replace 85 battery packs that fail under warranty, with refurbished packs.
If there was truly some sort of defect in the pack and cell design, why would they do this, and risk more bad press, aka, "Rebuilt Tesla battery explodes on way home from service center" instead of replacing them with new packs?
It is conceivable charge/battery/regengate were done out of an abundance of caution, but also has the effect of reducing warranty claims, so no reason to roll back the changes.
Because they don't have new packs that would fit the old 85's???? Maybe....
