Minimum battery charge for full power acceleration?

[DavidZemon]

I have a 2017 Model S 90D, but perhaps this post can be useful for others with different configurations as well.

I've heard that if the battery is not fully charged, you may not get full acceleration. I have not, however, seen any numbers put to it. Can someone enlighten me by telling me what battery state the car needs to see in order to unlock the highest power output for my car? Are there just two power output modes (a "low battery" mode and "normal"?) or are there multiple steps?

Thanks,
David

 

[ucmndd]

Power = volts x amps

Battery voltage drops as state of charge drops, but it's not linear. So at lower states of charge the battery needs to deliver more current to produce the same amount of power. Of course there's a limit to the amount of current the battery can produce and safely deliver to the motor, so power drops at lower states of charge.

This is more of an issue with performance models, because they operate at the ragged edge of what the battery can output and what the motors can take in. Non-performance models have their performance capped at lower levels, so there's no real effect at higher states of charge. I'd say power output on a 90D is pretty well maxed out at 80+% SoC and any performance difference between 80 and 100% would be negligible to imperceptible.

 

[DavidZemon]

Oh interesting, and here I'd assumed that with a non-performance model, the power was capped MUCH lower than the battery's capabilities.

 

[beatle]

I've also been curious about this, measuring performance of my car at various SoCs. At full tilt, Ludicrous+ is well north of 500hp when over 90%, but when below 20% the power output is under 400hp. This is measured with ScanMyTesla.

 

[BigNick]

For Ludicrous, I think you need 100% SoC to get true maximum power as it just tells Scotty down there in Engineering to give 'er all she's got, and the + mode (Max Battery) adds a bit more by heating the battery to optimal temperature.

There is no SAE standard of measuring electric car power that I know of so far, so most manufacturers will advertise specs at near 100% SoC. In normal circumstances you won't have that unless you're running Ludicrous+ while charging off a generator, and unplug immediately before your drag run.

I'm pretty sure non-P cars are limited, but I can't recall if it is by total amperage or kW or what the threshold value is.

 

[DavidZemon]

For Ludicrous, I think you need 100% SoC to get true maximum power as it just tells Scotty down there in Engineering to give 'er all she's got, and the + mode (Max Battery) adds a bit more by heating the battery to optimal temperature.

There is no SAE standard of measuring electric car power that I know of so far, so most manufacturers will advertise specs at near 100% SoC. In normal circumstances you won't have that unless you're running Ludicrous+ while charging off a generator, and unplug immediately before your drag run.

I'm pretty sure non-P cars are limited, but I can't recall if it is by total amperage or kW or what the threshold value is.

That is certainly what I was expecting to hear.

 

[beatle]

For Ludicrous, I think you need 100% SoC

I'm pretty sure non-P cars are limited, but I can't recall if it is by total amperage or kW or what the threshold value is.

This makes sense, though there is some additional controlling going on. With my car currently sitting at 88%, I have 4.08v per cell on average. Last I checked in July, my car is not voltage capped and still goes to 4.2v when fully charged, so there is more power to be had above 90%.

For non-P cars, I'm fairly certain they wouldn't cap the voltage; they'd just draw fewer amps. This is more efficient and easier on the components than running less voltage.

 

[AmpedRealtor]

I don't know about you P-D folks, but my P85 pulls great even at 40% SOC.