Every electric car keeps something back below zero, and almost none of them tell you how much. Out of Spec Testing set out to measure it on a Rivian R2 Performance, running the car from 5 percent state of charge down to a complete stop on a closed track at between 30 and 55 mph. The headline figure is that the car covered 8.1 miles after the display read zero percent while still holding 55 mph without complaint, which is a substantial hidden reserve. The problem is what happened at the end of it. The hosts are explicit that this is a controlled test and not something to try, since buffers vary between cars and shift as a pack ages and recalibrates.
Buffer testing matters more for electric cars than the equivalent low fuel light does for a combustion car, because the failure mode is different. Running a petrol car dry means a can of fuel at the roadside. An electric car that stops is usually a flatbed, and the hosts report that once this one stopped it could not be put back into drive at all, so even rolling it clear was off the table. That is the real world consideration a range number does not capture, and it is why the timing of the warning matters more than the size of the reserve. It is also why the test only worked as a test: Charge Rigs supplied a mobile DC fast charger that could be driven out to the stranded car on a closed track, which is not an option on a live carriageway.
The video logs the sequence. Out of Spec Testing says a slight power limitation appeared around 13 percent and became more noticeable near 8 percent, with a battery very low warning at 5 percent showing 18 miles of indicated range. At 3 percent the display showed 11 miles remaining after 4.2 miles covered, with average efficiency running at about 3.38 miles per kWh. At 2 percent the car displayed a message about reduced performance to conserve energy, though the driver reports no change he could feel. Zero percent arrived after 10 miles from the 5 percent start. From there the car held 55 mph on the straights with no further warnings for another 8.1 miles. Turtle mode then appeared alongside a performance limited message, and the hosts say propulsion vanished almost immediately afterward, leaving them coasting. Their criticism is that turtle mode should trigger when a car can no longer maintain highway speed rather than seconds before it stops. On the charger, they report a pack voltage of 296 volts under a 200 amp load and roughly 2.5 kWh of energy before the display moved off zero. They also flag a small inconsistency worth noting for anyone reading state of charge off a charger screen: the car continued reporting zero percent through the charge port while the dashboard had already ticked over to one, and later showed 10 percent on the display after being unplugged at nine. Only three warnings were logged in total and all of them cleared once charging began.
Bottom line: the reserve is generous and the warning strategy is not. Eight miles past zero at highway speed is a genuinely useful margin, but it is only useful if the car tells you when it is about to run out, and a turtle icon that appears moments before the motor quits gives a driver no time to get off a carriageway or pick a safe place to stop. This is a software fix, not a hardware problem, and it should be near the top of the list. Treat zero as zero until Rivian changes it.
Commentary on a third-party video. Figures and claims are as presented in the source and have not been independently verified. Spotted an error? Tell us and we will correct it.