Video: Sandy Munrow discusses Tesla Battery Day

[Crissa]

Why not just make it 801v or 750? Seems ez to do it if they wanted.

They'd have to change their motors, wiring, inverters, controllers, chargers, superchargers... And standard wiring goes to 600v so they'd have to get special wiring, too. (There's a reason the 800v cars so far have been really expensive.)

Or deal with the patent.

It's easier (for now) to ignore it and stay where production is cheaper. I hope they'll be keeping an eye out for how to make that jump in the future, but until then... I can kinda understand a little dismissal.

Wait until coildriver motors start coming out. That's another patent on 'we put relays in weird places' but at least it was hard to do.

-Crissa

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[ajdelange]

Why not just make it 801v or 750? Seems ez to do it if they wanted.

Well no, it's not easy to do. For one thing when you go above 600 V you enter the world of 'high voltage' per the NECs definition. A lot of the rules concerning wiring practices change. Safety regulations change too. People who service and build the car now need to be high voltage certified. Insulation demands become more stringent, wire/trace conformation needs more attention, connectors must be special high voltage connecters, disconnect means (fuses and breakers) become different and, most important, the active devices (semiconductors) must be able to withstand higher voltages when they are switched off. Munroe didn't specifically mention any of these things in his remarks but he alluded to several of them.

Now he did point out in words to the effect that some day they will figure all this out and of course more high voltage devices are available every day. The Lucid is going to be a 800 V car as are several others.

And what are the advantages of this higher voltage? The main one is that you can access higher power chargers because all the higher power chargers are 800 V (and up) and the reason for this is smaller, less expensive, more manageable cables. I don't think an 800 V 3ø motor is any more efficient than a 400 V 3ø motor and I don't think an 800 V battery is more efficient than a 400 V one. Are there some nuances with higher voltage transistors that I don't know about?

 

[restyle]

....And what are the advantages of this higher voltage? The main one is that you can access higher power chargers because all the higher power chargers are 800 V (and up) and the reason for this is smaller, less expensive, more manageable cables. I don't think an 800 V 3ø motor is any more efficient than a 400 V 3ø motor and I don't think an 800 V battery is more efficient than a 400 V one. Are there some nuances with higher voltage transistors that I don't know about?

As you say - Higher Voltages{V}means a lower Current{I} through the cables resulting in both copper cost savings & less weight.
Back to school time:-
Power {W}=V*I
Lets say Charging Power = 150Kw {150,000 Watts}
At 400 Volts, Charging Current =150000/400 = 375Amps {CSA of copper rqd =300mmsq}
At 800 Volts, Charging Current =150000/800 = 187Amps {CSA of copper rqd =70mmsq}
This effectively gives both a weight & cost saving by a factor of 4

As for nuances of higher voltage electronics rqd - I must have skipped tech school that day

 

[egandalf]

TSLA should have risen after Battery Day (had I more disposable cash I would have taken the opportunity to buy more stock).

I can only do a share at a time on occasion. Better believe I bought one more share when it took that dip!

 

[Newton]

I see, good insights. I figured they would have to change some things a bit, but sounds like higher voltages means a complete rework.

 

[Crissa]

Yeah, you save copper, but you gain in cost and insulation.

I wonder how compatible these 800v cars are with the existing CCS infrastructure? With CHAdeMO lots of the stations skipped park of the spec to save money, so were incompatible with 100v systems despite that being in the spec.

-Crissa

 

[ajdelange]

New wiring, new charger, new DC/DC converter, new inverter/rectifier, new traction motors, new compressor, new electric heaters, new circuit breakers, new control algorithms, new battery pack architecture, new BMS, new cooling system. What did I forget?

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