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New Launch Mode - firmware 2.9.40
- Thread starter PatP
- Start date
Eagerly waiting for your vbox video!! Hope this update has improved the 0-60 numbers.
lolachampcar
Well-Known Member
One thing I have not seen mentioned in any Tesla thoughts on battery performance is the issue of "skin charge" that I have seen and read about in the RC world. Basically, you pull your battery right off the charger and, for a short period of time, the voltage is a bit higher than normal and there is an extra bit of umph to it. Perhaps this is the result of the battery being warm from the charging but I have always heard it referred to as a little extra from the skin charge that dissipates rather quickly if you let the battery sit (after charging).
Any battery experts want to chime in here as I am well out on a limb.
Any battery experts want to chime in here as I am well out on a limb.
AGREED!
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full charge? Don't we only need around 90% for best acceleration times per Elon? Either way let's get those times!!!!
Elon stated that impedance is less at 90% than at 100%, so yes, 90% will result in faster launch than at 100%.
lolachampcar
Well-Known Member
and DragTimes has a wee bit of experience with performance testing cars and then sharing data.
lolachampcar
Well-Known Member
That was my interpretation as well. When first reading the "pedal action" description, my gut reaction was "here comes more people plowing thru storefront windows" -- until I noticed the Max Battery gating step.
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It's not pointless if it's required to deliver the 10.9 promise sold to P90D/L owners. Just sayin'.
I'll take it upon myself to chime in even though I'm not a battery expert, just an electric vehicle geek with no engineering background who spends a lot of time reading about stuff like this. However, from what I know, battery pack stores DC voltage whereas the motor uses AC voltage. So the power electronics should be regulating the the DC pack voltage to a preset AC voltage that the motor would like. So why would it matter if the pack voltage was 10-20V up or down?
Maybe those RCs with the skin charge effect used DC motors hence not requiring a regulation in between the pack and the motor? Don't know.
I too would like to see .02$ of an EV expert.
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Andyw2100
Well-Known Member
Your secondary reaction wasn't "here come more people plowing through sotre front windows with warm batteries?"
If they were doing this right it would also prevent them from recognizing revenue on ludicrous mode until this is delivered...
lolachampcar
Well-Known Member
emir,
Oh, that one is just too easy......
Power from a battery is current times voltage (P=IV) so up the voltage and you get more power
Oh, that one is just too easy......
Power from a battery is current times voltage (P=IV) so up the voltage and you get more power
lolachampcar
I do know that but what I was trying to say is; isn't there a transformer somewhere in between the pack and the motor that regulates DC voltage into AC? I am assuming here that AC motor always likes a specific range of voltage and it gets regulated. To give an example; (all assumptions)
SoC 100% --> Pack voltage 400V
You demand power from the motor with your right foot, 403V DC gets converted to 375V AC (why not 375 for the sake of the example) and your foot decides the amps you'll get out of it.
SoC 50% --> Pack voltage 370V (again, all assumptions)
You demand power with your right foot, 370V DC converted to 375 AC again (via the transformer) and your foot decides the amps for the kW needed.
But there's far more into this than I don't know. Heck even charging voltage we see whilst supercharging and pack voltage when discharging is different. Also, when you floor it, there's this battery phenomena called pulsing where voltage drops a lot and gets back up after you stop flooring it. All of this is just stuff I read about online but of course lack the expertise and detail. So I'd love anyone with more and thorough knowledge to chime in and any suggested reading is much appreciated.
I do know that but what I was trying to say is; isn't there a transformer somewhere in between the pack and the motor that regulates DC voltage into AC? I am assuming here that AC motor always likes a specific range of voltage and it gets regulated. To give an example; (all assumptions)
SoC 100% --> Pack voltage 400V
You demand power from the motor with your right foot, 403V DC gets converted to 375V AC (why not 375 for the sake of the example) and your foot decides the amps you'll get out of it.
SoC 50% --> Pack voltage 370V (again, all assumptions)
You demand power with your right foot, 370V DC converted to 375 AC again (via the transformer) and your foot decides the amps for the kW needed.
But there's far more into this than I don't know. Heck even charging voltage we see whilst supercharging and pack voltage when discharging is different. Also, when you floor it, there's this battery phenomena called pulsing where voltage drops a lot and gets back up after you stop flooring it. All of this is just stuff I read about online but of course lack the expertise and detail. So I'd love anyone with more and thorough knowledge to chime in and any suggested reading is much appreciated.
MarcG
Active Member
I recently saw a Model S with a license plate that will remind us all of this :biggrin:
lolachampcar
Well-Known Member
emir,
Sorry for being a smart arse.... Inverters do not "convert" DC to AC as much as they switch DC from the battery to differing windings in the motor which, when you look at the inductive charging of the winding, looks a lot like AC. The overall power as a function of input voltage and current ends up ruling the day.
Sorry for being a smart arse.... Inverters do not "convert" DC to AC as much as they switch DC from the battery to differing windings in the motor which, when you look at the inductive charging of the winding, looks a lot like AC. The overall power as a function of input voltage and current ends up ruling the day.
dirkhh
Middle-aged Member
True. Now one could argue that Tesla would have been better off not making promises they couldn't keep - but then we derail this thread talking about communications @ Tesla :-/
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