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CharonPDX
Well-Known Member
They are. Those two numbers are just the "average nominal voltage." Voltages vary by up to 200 Volts from those values for a given powertrain.
Rivian actually uses closer to 450V when charging, while Hummer is closer to 350V/700V. (350V while driving, 700V while charging.) It's one of the reasons that some "150 kW" stations can charge a Rivian faster than 150 kW, because the station's limit is actually amperage, not "total power." On the other side, some lower-voltage EVs can't even get closer to 150 kW on a "150 kW" station, because they max out the Amperage before hitting 150 kW total power.
"800V" even includes up to 1000V.
Then the voltages also change during charging. When you first start charging a vehicle, it will be at higher voltage, and as it gets closer to full, the voltage will drop to barely above the "base pack voltage", and stay there the rest of the charge cycle, ramping down Amperage as the pack gets closer to full.
Rivian actually uses closer to 450V when charging, while Hummer is closer to 350V/700V. (350V while driving, 700V while charging.) It's one of the reasons that some "150 kW" stations can charge a Rivian faster than 150 kW, because the station's limit is actually amperage, not "total power." On the other side, some lower-voltage EVs can't even get closer to 150 kW on a "150 kW" station, because they max out the Amperage before hitting 150 kW total power.
"800V" even includes up to 1000V.
Then the voltages also change during charging. When you first start charging a vehicle, it will be at higher voltage, and as it gets closer to full, the voltage will drop to barely above the "base pack voltage", and stay there the rest of the charge cycle, ramping down Amperage as the pack gets closer to full.
Dark-Fx
Well-Known Member
You might not be able to charge very far into the pack at CCS stations that are limited at 500V.
The reason ultimately comes down to what voltage the power electronics are rated for. Common ones are 400, 600, 1000. But those aren't the only ratings for things. You have to have some flexibility on voltage in case of surges.
Rivian's maximum allowed voltage is currently 459V, above that it is supposed to disconnect the contactors. I have no plans to dissect any of the power electronics nor the battery pack in my own truck to find out what the actual limitations might be.
CharonPDX
Well-Known Member
Those are just the two Voltages that have been standardized on. Older CCS stations were "400V only", and supported supplying up to 500V. The newer ones essentially all support any random voltage between ~300V and 1000V.
One big thing about batteries is that to charge them, you need to have voltage higher than the pack is currently at. So if a battery pack is at 600 Volts, some of the older CCS stations wouldn't be able to supply enough voltage. 800V vehicles all have 1/2 converters, so they can accept 400V input, but they'll charge at half the rate they should be capable of. But they can't just accept arbitrarily high, either. A "400V nominal" pack can't just cram 800V. It needs to be the acceptable voltage range. So a "400V" pack may take 450 Volts early on, then need to taper down to 410 Volts.
A 600V vehicle would need to drop to 300V, and suddenly it's at the very minimum of the CCS spec, and would charge very slowly indeed. If you plugged in to a "50 kW" station, you'd probably only get about 30 kW. Which on a Max Pack, would be agonizingly slow. (I've charged my "Large Pack" R1T on a 50 kW station, the first weekend I owned it. That 2 hour session was bad enough. I can't imagine charging at an even lower rate with a bigger pack.) and some CCS stations may not support arbitrary voltages - they may *ONLY* support "300-500V or 700-1000V" with no 500-700V range at all, due to being natively either 400V or 800V, and using a 1/2 or 2x step-up or step-down converter to handle the other one.
There's a reason carmakers keep them at "about 400V" or "about 800V". Because that's what the infrastructure has been built for. If Rivian really wanted to go it their own way and have the Rivian Adventure Network optimized for 600V, sure, they could do it, and get 300 kW or more out of their own custom chargers.
One big thing about batteries is that to charge them, you need to have voltage higher than the pack is currently at. So if a battery pack is at 600 Volts, some of the older CCS stations wouldn't be able to supply enough voltage. 800V vehicles all have 1/2 converters, so they can accept 400V input, but they'll charge at half the rate they should be capable of. But they can't just accept arbitrarily high, either. A "400V nominal" pack can't just cram 800V. It needs to be the acceptable voltage range. So a "400V" pack may take 450 Volts early on, then need to taper down to 410 Volts.
A 600V vehicle would need to drop to 300V, and suddenly it's at the very minimum of the CCS spec, and would charge very slowly indeed. If you plugged in to a "50 kW" station, you'd probably only get about 30 kW. Which on a Max Pack, would be agonizingly slow. (I've charged my "Large Pack" R1T on a 50 kW station, the first weekend I owned it. That 2 hour session was bad enough. I can't imagine charging at an even lower rate with a bigger pack.) and some CCS stations may not support arbitrary voltages - they may *ONLY* support "300-500V or 700-1000V" with no 500-700V range at all, due to being natively either 400V or 800V, and using a 1/2 or 2x step-up or step-down converter to handle the other one.
There's a reason carmakers keep them at "about 400V" or "about 800V". Because that's what the infrastructure has been built for. If Rivian really wanted to go it their own way and have the Rivian Adventure Network optimized for 600V, sure, they could do it, and get 300 kW or more out of their own custom chargers.
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