I am glad they went to 800V. The acceleration stat race is getting a bit stupid. But I think 800V is very important, at least for charging. It will not only let you charge fast it will let other people use the charger after you are done.
I hope the industry moves both the fast chargers and the cars to 800V asap. (Naturally, fast chargers should retain 400V backward compatibility). When cars charge faster it is kind of like having more chargers.
800V lets them have all the HV conductors within the car half the thickness.
Back in 2015, it didn't make sense because EV's didn't charge that fast, and battery balancing tech was still expensive (and cost scales proportional to the voltage).
However, now battery balancing tech is mere cents per volt, and customers demanding fast charging means super thick (and expensive!) wires in the car and battery pack.
1000 volt MOSFETS have also become a lot cheaper (used in the motor inverters), whereas before car manufacturers were reusing 600 volt mosfets designed for other things.
The only downside of higher voltages are increased insulation requirements. However, PVC insulation allows 10kV per mm, so the insulation thickness required is still tiny (although clearly you cannot use outdoor air as an insulator in either case).
The 800v is not relevant to “all the conductors within the car“. It is the move from 12 V to 48 V that allows them to reduce the thickness of all the wires within the car. That’s what the cybertruck introduced.
> The only downside of higher voltages are increased insulation requirements.
Is there increased risk to emergency responders who might have to cut into a vehicle to rescue occupants? Or is there a possibility that deformation from an accident could result in metal parts charged to 800V? I hope things are designed to prevent that. Perhaps the insulation you mention is armored for the high voltage paths.
400V is already beyond dangerous, raising it won’t kill you any faster. There’s probably decreased risk because of lower current (less heat to melt things).
EVs have a system that disconnects the battery mechanically when a high speed impact happens. I don’t think there have been any electrocution incidents so far?
Good. They are designed to prevent injuries to first responders (which are nearly always exposed to some hazard when responding to a vehicle accident.)
I did a search and could find no reports of injury to first responders.
Is EV charging actually voltage limited? I had impression that it's limited more by C rating and upstream capacity than by resistance and/or cable thickness requirements.
Somewhat? This voltage isn’t (just) about the battery, but about all power connections. Cables can only take so much current after all! At 150 KW, you need 400 V × 375 A. That is an insane current figure. At 800 V, it’s just half the current.
I’ve used a 300 KW DC charging station once. The cable is very thick and heavy. There are practical limits.
Cable thickness is very much a problem with fast chargers. Many fast chargers now have water cooled cables, because when 500 amps is going down the cable, you either need it super thick with copper or to have the complexity of two water cooling loops (one for the positive conductor, one for the negative conductor, electrically isolated coolant loops).
> The base model, however, only supports 400V charging for its smaller 73.6kWh battery,
This suggests the base model is 400v, while the other models are 800v.
That in turn means that the onboard charger, DC/DC, motor inverters and AC compressor inverter must be different between the models, or that they have designed 400v/800v dual-mode hardware for all those things.
Having so many parts different between models drives up costs.
Having dual-mode hardware also drives up costs - typically the power electronics have cost ~proportional to max voltage * max current. If you need a fixed output power, you are only using half of either voltage or current if the hardware is dual-mode, so you are wasting half of the power electronics cost, which is huge.
(before someone points out that Tesla cybertruck has dual-mode 400v/800v since it can rewire the battery to charge at either voltage... Well it never drives along in the 400 volt mode. And even then, I'd bet the AC compressor is at dramatically reduced power output while on a 400v charger)
It might be a long term cost savings measure if trials with 800v allow them to move their whole fleet to 800v eventually and lower costs in the future.
I hope the industry moves both the fast chargers and the cars to 800V asap. (Naturally, fast chargers should retain 400V backward compatibility). When cars charge faster it is kind of like having more chargers.