LostVector
Member
Of course I do not know for a fact that this very particular mode of failure is what's going on in OP's battery, but it's called out in the presentation and clearly OP's battery is defective in some way. Averages and expected behaviors do not apply.Electrolyte oxidation happens at very high voltage - in general above the maximum voltage lithium ion batteries use.
4.20V/cell is the 100% that Tesla use. The examples in Jeffs presentation is above 4.20V.
You're assuming the battery pack is degrading in a normal way. It clearly hasn't and so isn't there a different failure mode at play? Imagine something was out of tolerance on one or a few batteries in the pack and there's a faster than expected buildup on the electrodes causing a few cells to start losing capacity quickly. It does not have to be a high charging voltage causing the issue.I havent studied the electrolyte oxidation specifically but I would guess that this is a non issue for EV users.
We do not use high voltage that often in general, as daily charging is ~80-90% (4.0-4.1V) or below. Most of us do not cycle the cells to 4.20V each time.
The point is I do not think you can look at studies designed to measure and predict the behavior of batteries within design spec when in all likelihood something is out of spec.
The failure mode described do not mean this. It means that the cell rapidly looses capacity in a low number of cycles, and then die - dead like in not possible to charge.
I'm a little unclear on what you are arguing relative to what I said about sudden drop in voltage and shutdown by the BMS.
Why do you think this is the case? I was under the impression that the BMS can get a more accurate reading when the battery has rested, but there are still certainly many data points that can be collected while the battery is under load to continue updating the SoC. Do you have a different understanding of this?When EV’s stops at whatever percentage above 0% displayed it do come from the fact that SOC can not be measured when driving (or charging).
Again, rested is the best way to measure it, but I don't understand it as the *only* way.The State of charge is measured by measuring the resting voltage (OCV) of the battery (-cells).
I agree? But also this seems a bit tautological?When driving (or charging) the BMS need to calculate the estimated SOC.
The calculation depends on the estimated capacity (and also the SOC). Any fault in estimated capacity or estimated SOC before the drive ends up in a error in the resulting estimated SOC we se on the display.