Tooney

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I know very little about the way EV batteries work. Below I have extracted some statements from the article, some of which imply that they apply to EV batteries in general, not just the Taycan.

Can anyone with knowledge of EV battery technology comment as to whether the statements below are true about EV batteries, or have any technical feasibility?

Not asking about the merits of the article as a whole, just these statements:
  1. “The battery cells in a BEV are always charged in parallel to shorten the charging time, but this carries the risk that some cells will be charged faster than others. If one of the many cells in a BEV is charged faster than the rest, overcharging and overheating can occur, which can lead to vehicle fires, if, for instance, an additional air leak happens.”
  2. “For safety reasons, overheated battery cells are disabled and isolated from the battery pack, reducing battery capacity and thus the vehicle’s range.”
  3. “It is a well-known risk in the industry that when charging BEVs, an imbalance in the battery cells can lead to a sealed, encapsulated, and deactivated cell that can then overheat and cause battery damage and even fires if, for example, there is an additional leak in the battery box through which air can enter. Porsche’s 800V high-voltage architecture is more vulnerable in this regard than a low-voltage architecture such as Tesla’s 400V, or what other manufacturers use.”
  4. “Most of the BEV battery fire-related problems recorded in the past typically occurred in low-cost BEVs that lack sophisticated battery management systems or onboard chargers.”
  5. “The problem occurs when the batteries are charged at a low AC speed of up to 7.5 KW, a common use case for all charging, such as at home or on low-speed chargers, … “
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porsche_coyote

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I know very little about the way EV batteries work. Below I have extracted some statements from the article, some of which imply that they apply to EV batteries in general, not just the Taycan.

Can anyone with knowledge of EV battery technology comment as to whether the statements below are true about EV batteries, or have any technical feasibility?

Not asking about the merits of the article as a whole, just these statements:
  1. “The battery cells in a BEV are always charged in parallel to shorten the charging time, but this carries the risk that some cells will be charged faster than others. If one of the many cells in a BEV is charged faster than the rest, overcharging and overheating can occur, which can lead to vehicle fires, if, for instance, an additional air leak happens.”
  2. “For safety reasons, overheated battery cells are disabled and isolated from the battery pack, reducing battery capacity and thus the vehicle’s range.”
  3. “It is a well-known risk in the industry that when charging BEVs, an imbalance in the battery cells can lead to a sealed, encapsulated, and deactivated cell that can then overheat and cause battery damage and even fires if, for example, there is an additional leak in the battery box through which air can enter. Porsche’s 800V high-voltage architecture is more vulnerable in this regard than a low-voltage architecture such as Tesla’s 400V, or what other manufacturers use.”
  4. “Most of the BEV battery fire-related problems recorded in the past typically occurred in low-cost BEVs that lack sophisticated battery management systems or onboard chargers.”
  5. “The problem occurs when the batteries are charged at a low AC speed of up to 7.5 KW, a common use case for all charging, such as at home or on low-speed chargers, … “
Most of these statements mix fact with bullshit. Taken in order:

1. Yes, battery cells are charged in parallel, and at a given ambient temperature a battery cell that's being charged at a higher rate will typically be warmer. This is why every battery management system measures voltage, temperature, and internal resistance of each cell and balances charging load to minimize this issue.
2. Uhh, sure.

3. Uhh, huh? The basic 'fact' here is that a damaged cell is more susceptible to fire. I guess so, but it depends on what's actually wrong with the cell. Also, the cells in an 800V pack are not different in voltage, the pack is. I believe that 400V and 800V EVs *with similar cell architecture* will have identical cell voltages. They just run more cells in series to increase the pack voltage. You can think of the number of cells in series in a pack as governing the voltage, and the number of cells in parallel as governing both the capacity and discharge rate. This is a bit of an oversimplification, but good enough for this discussion. Almost all Li-ion battery cells used in EVs today have a nominal voltage of 3.7V, Tesla and Porsche included.

4. "Most of the BEV fire-related problems..." Is the author referring the Bolts?

5. "The problem occurs when..." I honestly can't comment on this without knowing more about Porsche's battery management system, but it would be a colossal oversight if lower-power level 2 charging damaged a pack. In most cases, it's far kinder to the cells to charge at lower power.
 

manitou202

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I really doubt there is any truth to the article, but for me the really sad part is the comment section of Teslarati. Do these people really want other EVs to fail? Do they cheer when a non-Tesla EV burns to the ground? What the f**k is wrong with these people?
 

Kingske

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I really doubt there is any truth to the article, but for me the really sad part is the comment section of Teslarati. Do these people really want other EVs to fail? Do they cheer when a non-Tesla EV burns to the ground? What the f**k is wrong with these people?
It is a very strange phenomenon. Why do some owners of a Tesla car behave like they are members of a sect?
 


Mike in CA

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Just a few moments ago I received an email from a Tesla fan and friend gloating and referencing this article. Let the bullshit fly!
And right there you have a perfect example of the audience for whom this article is really written and why it appeared first in such a well-respected and objective venue (ha) as "teslarati.com". :rolleyes:
 
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F16HTON

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60% is 6 of 10 Taycan owners. With the TaycanForum members affinity to bitch about anything, we would have surely heard about these issues long before the writer to Teslarati would have.

This is the only post on Teslarati by Alex Voigt, but he sure loves to write for CleanTechnica, although it appears that ceased about a year ago.
 


Reg

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This guy is really trying to milk this. I also like how his weirdly worded disclaimer about Porsche stock and "derivates" in no way precluded that he is shorting VW/Porsche.
Oddly, he doesn't say anything about whether he has a financial stake in Tesla - even though he mentions that Tesla was going to help Porsche and some other nonsense.

Good reminder on that tweet. It went from a former employee to a current employee. wonder if it is the same person or he is now saying there are two sources.
 

Torv

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60% is 6 of 10 Taycan owners. With the TaycanForum members affinity to bitch about anything, we would have surely heard about these issues long before the writer to Teslarati would have.
No shit! This forum would have lit up like a Christmas tree on acid if this were a thing. How many Taycan owners are represented here? 500? 1000? The sturm und drang here would have been deafening If this were anything close to real.
 
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batteredhaddock

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Most of these statements mix fact with bullshit. Taken in order:


5. "The problem occurs when..." I honestly can't comment on this without knowing more about Porsche's battery management system, but it would be a colossal oversight if lower-power level 2 charging damaged a pack. In most cases, it's far kinder to the cells to charge at lower power.
Agreed. Given Porsche have just updated guidance on the 22kW option to charge at 6kW on single phase to protect the charger lifetime they clearly don’t see lower rates of charge as any issue at all for the cells. (sure they’d rather replace a charger than a battery pack if it were the opposite way around… ). What a muppet……
 

epirali

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Some real information below:

Not asking about the merits of the article as a whole, just these statements:
1. “The battery cells in a BEV are always charged in parallel to shorten the charging time, but this carries the risk that some cells will be charged faster than others. If one of the many cells in a BEV is charged faster than the rest, overcharging and overheating can occur, which can lead to vehicle fires, if, for instance, an additional air leak happens.”
In all LiIon battery multi cell designs do what is called overcharge protection, "cell balancing" to adjust for cells charging at slightly different rates. This has always been true, and it NOT a fire hazard. If a cell in a group is ever much lower than others it leads to the group not being able to deliver more energy that the weakest cell. This is battery depredation and can result in reduced capacity. The rest is just nonsense.

If a cell gets overcharged then there was a design failure.

2. “For safety reasons, overheated battery cells are disabled and isolated from the battery pack, reducing battery capacity and thus the vehicle’s range.”
This is bull, I have not seen any battery design yet in cars that "disables" a cell. You can't just remove one cell.

3. “It is a well-known risk in the industry that when charging BEVs, an imbalance in the battery cells can lead to a sealed, encapsulated, and deactivated cell that can then overheat and cause battery damage and even fires if, for example, there is an additional leak in the battery box through which air can enter. Porsche’s 800V high-voltage architecture is more vulnerable in this regard than a low-voltage architecture such as Tesla’s 400V, or what other manufacturers use.”
Most of this is incorrect or incomplete. Specially the 800v vs 400v. The 800v architecture has many benefits, including as others have pointed out less current required to flow around to do the same amount of work. The 800v architecture is a significant advantage in design and I can see why Tesla "supporter" would want to make it seem like its a bad thing. It allows for much faster charging and better power delivery.

4. “Most of the BEV battery fire-related problems recorded in the past typically occurred in low-cost BEVs that lack sophisticated battery management systems or onboard chargers.”
I have no idea what this refers too. Forgetting very low volume or compliance cars the Nissan Leaf was the first non Tesla EV with lots of units. And the design flaw in the early Leaf had to do with only using air cooling (inadequate in hot environments) which led to battery degradation NOT any fires or "cells" failing. In fact Nissan changed battery chemistry in 2013 to address this with what was referred to commonly as the "lizard battery." This was bad in states like NM, AZ, TX etc.

5. “The problem occurs when the batteries are charged at a low AC speed of up to 7.5 KW, a common use case for all charging, such as at home or on low-speed chargers, … “
Not sure what the "problem" that occurs is exactly that happens as low speeds/current but not high ones. Fast DC charging is more stressful to any battery and may expose weak cells more quickly, but that applies to all cars. Low speed charging is actually less stressful.

The whole thing makes no sense and reads like a targeted FUD article.
 

McgR

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When I bought my X5 PHEV two years ago a similar thing happened. X5’s started to catch fire all over the world and lots of bad reports on forums. I was still waiting for my car and I tempered my enthousiasm with the new car.

At the end everything turned out well.

I did install a fire alarm in my garage. I think this is a good idea anyway when charger a car inside.

I still have to install a wall box. I was thinking it might be a good idea to put it outside. I will have to charge once or twice I week. Or can charge with the standard 2,3 kw charger over night. That is what I do know with the 20 kWh battery of the X5.
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