Does supercharging controller rotate cells?

[izzzyyd]

So when supercharging does the charge controller rotate battery cells?

Meaning I’m charging at 200KW from 10-20% are the same cells getting constantly hit with 200KW?

Or does it rotate cells throughout the whole pack through some algorithm so they age evenly?

 

[E90alex]

Power is split between all the cells at the same time when charging and discharging.

 

[izzzyyd]

Power is split between all the cells at the same time when charging and discharging.

Ahh ok sweet, also the reserved 5-10% capacity Tesla keeps does that get rotated into the mix also?

 

[izzzyyd]

Also random question say a cell goes bad is there a way to just disable it and go on your merry way? With obviously less capacity.

Would be kind of cool instead of repairing the battery, just disable non functioning cells.

 

[stopcrazypp]

Ahh ok sweet, also the reserved 5-10% capacity Tesla keeps does that get rotated into the mix also?

The bottom buffer is Tesla simply not discharging below a certain SOC. You seem to be thinking they keep cells in reserve that are not discharged, but that is not how it works. All the cells are discharged at the same time. As such there is nothing to "rotate".

Also random question say a cell goes bad is there a way to just disable it and go on your merry way? With obviously less capacity.

Would be kind of cool instead of repairing the battery, just disable non functioning cells.

No, there is no way to remotely disable a certain cell. However, if the cell fails open (it burns out in a way that disconnects it), the pack will work fine, just with a capacity proportional to the amount of parallel cells still active in the weakest group.

In my SR+ the configuration is 96S31P (S being in series, P in parallel). That means if a cell dies, the pack loses 1/31 of its capacity. The reason why it loses based on parallel is because of how battery balancing works, a pack is only as strong as its weakest parallel group.
What is the nominal battery voltage for the Tesla Model 3 batt pack options?

 

[izzzyyd]

The bottom buffer is Tesla simply not discharging below a certain SOC. You seem to be thinking they keep cells in reserve that are not discharged, but that is not how it works. All the cells are discharged at the same time. As such there is nothing to "rotate".

No, there is no way to remotely disable a certain cell. However, if the cell fails open (it burns out in a way that disconnects it), the pack will work fine, just with a capacity proportional to the amount of parallel cells still active in the weakest group.

In my SR+ the configuration is 96S31P (S being in series, P in parallel). That means if a cell dies, the pack loses 1/31 of its capacity. The reason why it loses based on parallel is because of how battery balancing works, a pack is only as strong as its weakest parallel group.
What is the nominal battery voltage for the Tesla Model 3 batt pack options?

Gotcha I have the SR+ too, I’m assuming this architecture lowers the actual failure rate requiring refurbishing?

But I guess you can have a soft failing pack meaning it loses a crap ton of capacity

 

[stopcrazypp]

Gotcha I have the SR+ too, I’m assuming this architecture lowers the actual failure rate requiring refurbishing?

It's part of a fault tolerant design from the Roadster days when they were using commodity 18650 cells. It allows a defective cell to be safely ignored if necessary.
http://large.stanford.edu/publications/coal/references/docs/tesla.pdf

The other reason is 96S is commonly chosen for EVs is because it gives 400-ish Volts (fully charged 4.2V*96 = 403.2V) which is what most high voltage components are designed to work with. That leaves the rest to necessarily be parallel. Roadster used a similar 99S (in 11 bricks of 9S), but Model S switched to an even number of modules (16 of 6S) so 96 works better. Model 3 also has an even amount (4 modules of 24S), so again 96 works better.

There are newer EVs however that work on a 800V architecture so would have more in series, but Tesla have not switched yet.

But I guess you can have a soft failing pack meaning it loses a crap ton of capacity

Yes, this has happened to Roadster packs. If a cell turns resistive (meaning it starts drawing power like a resistor) instead of failing open, it can drag down the whole pack, to the point it may mean complete failure.
How well are Roadster Battery Packs aging? | Gruber Motors