Rivian AC charging curve is weird. Why?

[C12farmer]

Here is another data set. Data is pulled every minute by the EVSE. This is at an office so we run at 208VAC nominal. I'm sure is some additional voltage drop happening between the EVSE and the Rivian onboard charger.

I think the line voltage is fluctuating depending on other facility loads like all the different air conditioners turning on/off.

It's interesting that the R1S only pulls the full 48A when the voltage is above a certain threshold.
In the posts above, others are charging at ~240V so the fluctuations there are not caused by some low voltage limit of the onboard charger.

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[Riviaenz]

I've noticed that Rivians (I've seen this with 3 vehicles now so I know it's not an anomaly with a single vehicle) have a very unstable charging rate on AC.

I've had extensive experience with Ford EVs and Tesla and they charge a pretty stable rates. Rivian on the other hand is all over the place. When set to 48 amps, it VERY loosely is kinda somewhere around 10.7Kw ish. But not stable at all

Totally not of consequence but curious if anyone has thoughts as to why it does that

Looks like it's with a 3rd party EVSE. Have you tried with the Rivian EVSE? I've noticed similar 10.5-11kWhr charging with a Wallbox but when I plug into our Rivian one it's pretty stable and holds to 11.2+ throughout the session (although that's usually when it's colder outside). I haven't used it much when it's hot out but it does seem to be slower when ambient temps are warmer. Our ChargePoint was also stable (although slow with a peak of 7.6kW). Still I prefer using our Wallboxes over the Rivian one since they log total charging and estimated costs. Plus our utility can manage our Wallboxes to pay us for when they delay charging during peak usage periods (easy to override if needed).