what is the voltage system for the Rivian compared to Tesla?

[Billyk24]

Don't know the exact wording/terms but is the Rivian have a 800 volt system installed making it far more robust and powerful than the Tesla? Also able to charge faster at the level 3 chargers?

Sponsored

 

[ajdelange]

I think Porsche is the only manufacturer currently talking about 800 V systems at the moment though Rivian does have a patent involving parallel/series switching of 400 V packs should 800 V charging become widely available at some time in the future. I have seen nothing to suggest that the early production R1T or R1S would have this feature as it would only add expense with little benefit at this point in time. 800V charging does not have the potential (no pun intended) to make the system more "robust and powerful". The only advantage it confers is faster charging.

 

[Billyk24]

Thank you. Question, Electrify America has 150-350 kWh fast charging capacity. I don't believe any of the current in production or near retail production vehicles can utilize 350kWh except maybe Porsche. Is it correct that a 800V system will be able to handle 350kWh chargers and thus faster faster charging capabilities?

 

[thrill]

This article covered pretty well Rivian's thinking and preparations for 800v charging.

https://www.greencarreports.com/new...ready-for-future-800v-upgradepossibly-in-2022

 

[Billyk24]

Good news to read. Thanks.

 

[ajdelange]

The battery packs are made up of a number of cells. Consider the simplest case of 2 cells of V volts each. You can put them in parallel and apply voltage V across the pair which, if it forces I amps through each will result in I*V watts being delivered to each cell for a total charge of 2*I*V watt hour in an hour. Or you can put them in series and apply 2V volts to the string forcing I amps through it. As half the voltage appears across each the charge picked up is again I*V watt hours per hour for each. The significant difference is that the cable that connects the battery pack to the charger carries twice the current in the parallel connection scheme and the power lost in that cable is therefore 4 times the power lost in the series connection with half the cirrent.

350 kW at 350 V means 1000 amperes. If a charging cable had a resistance of 0.001Ω the heat loss in it would be 0.001*1000000 = 1000 Watts. That's a fair amount of heat. If you can double the voltage to 700 volts the current goes down by a factor of 2 and the power dissipated by a factor of 4 to 250 watts. The Rivians are going to have a 180 kWh battery pack. If you can cram 350 kW into it you can charge it in 180/350 hr i.e. about a half hour whereas if you must charge at 150 kW then it will take 180/150 i.e. 1.2 hr.

You rarely take on a full charge - more like half to perhaps 80% of one so we are talking 15 - 30 minutes as against 36 - 54 minutes. Is this really that big a deal to the point that the public will demand the faster chargers?

Apparently EA has installed a handful of 350 kW chargers in California. I just can't see 1000A so I assume those must be 800 V. And Porsche installed a few in Germany a couple of years back. At the moment I see this as marketing more than anything else but the Rivian's and Cybertrucks will consume more than other BEVs and the market for these things may evolve.

 

[electruck]

As one might expect, there is a penalty for being an early adopter.

Not really a big deal for daily around town commutes but a huge deal for those making frequent long highway trips. However, It's still not completely clear to me how amenable currently battery chemistry is to frequent fast charging.

 

[Billyk24]

Electrify America has 412 locations with 1407 CCS 150 to 350 kWh chargers, 412 CCS-ChAdeMo chargers, 92 level 2 chargers. Another 106 sites are to be opened in 2020.

 

[MattpR1T]

So the systems are 400v nominal which is the current norm but Rivian’s has a patent to switch two halves of the battery to series when charging and back to 400v for the traction motor.

Don't know the exact wording/terms but is the Rivian have a 800 volt system installed making it far more robust and powerful than the Tesla? Also able to charge faster at the level 3 chargers?

 

[ajdelange]

Rivian has a similar patent/

 

[MattpR1T]

That’s who I was referring. Tesla’s operate at sub-400v nominal.

 

[ajdelange]

Am I losing my mind? I'd swear there was a name that wans't Rivian in No. 9 a minute ago. I did wonder if whoever that was was a Rivian employee though.

 

[MattpR1T]

You’re not, I corrected it but it was an autocorrect error to Rogers nowhere close to Tesla.

 

[ajdelange]

In fact I am but this evidently isn't a manifestation. Thanks for the brief reprieve.

 

[Hmp10]

Ajdelange, perhaps you can help me here with your electrical engineering knowledge. Lucid Air is going to use a 900+ volt system. Their technology chief says that it doesn't confer any significant advantage with charging speed. He says the primary advantages lie in reducing battery impedance, especially at high discharge rates during speed driving; in reducing cooling requirements; and in enabling more efficient inverter design and lighter and smaller motors.

An engineer on a Tesla thread has claimed these are all bogus claims, and that higher voltage confers no advantages other than very marginal savings in cabling materials and weight.

What's your take on this?

Sponsored