Valtteri Bottas’s final-lap crash at the Azerbaijan Grand Prix had an unusual technical cause, with his Cadillac’s control unit becoming confused after the Finnish driver went long at Turn 1. The extra distance he covered altered the car’s energy-management calculations, eventually triggering aggressive super-clipping and leaving Valtteri Bottas without regenerative braking when he reached Turn 15.
The sequence explains an incident that received little attention during the live broadcast. With the television coverage focused on the fight for victory and the battles further up the midfield, Valtteri Bottas’s accident was not replayed. By that stage, the Finnish driver was already at the back of the field, around 20 seconds behind Sergio Perez and with no apparent reason to be pushing beyond the limit.
Technical cause behind Valtteri Bottas’s Baku crash
There was, however, a technical explanation for Valtteri Bottas hitting the barriers at Turn 15. Shortly before the braking zone, the control unit had remapped several parameters associated with battery regeneration, effectively leaving the Cadillac driver without regenerative braking.
In practical terms, the confusion within the electronics deprived Valtteri Bottas of part of the car’s normal braking force at one of the most demanding braking points on the Baku circuit.
That raised another question: what had confused the electronic “brain” of the Cadillac MAC-26 in the first place?
Turn 1 off changed the distance travelled
The explanation begins several kilometres earlier, at the start of the same lap. Valtteri Bottas went too deep under braking for Turn 1 and ended up in the escape road. To return to the circuit, the Finnish driver had to turn the car around in the run-off area, meaning he covered more metres than he normally would during a lap.
That additional distance caused problems for the control unit, which estimates where the car is on the circuit based on the distance travelled during the lap and adjusts the use and distribution of electrical energy accordingly.
Because Valtteri Bottas had travelled further than expected before reaching Turn 15, the car’s electronic “brain” began remapping several parameters. That ultimately created the confusion that deprived him of regenerative braking.
How Cadillac’s energy deployment works before Turn 15
From an energy-management perspective, the acceleration zone between Turn 12 and Turn 15 can be divided into two distinct sections. During the first phase, the electric motor contributes to propulsion, but its assistance is progressively reduced until it is completely cut.
The car then enters the second part of the section using only the internal combustion engine, allowing electrical energy to be conserved for the long straight that follows.
Only at the very end of this phase, if required, can the car enter what is described as super-clipping. In this state, the electric motor works against the internal combustion engine to recharge the battery, although this would normally occur only over a relatively short section.
Early super-clipping cost Bottas around 60 km/h
In Valtteri Bottas’s case, however, the additional distance created by his Turn 1 excursion caused the control unit to send the power unit into super-clipping earlier and more aggressively than intended in an attempt to recover energy, even at a point where doing so was not strictly necessary.
It quickly became clear that something was not working correctly. As Valtteri Bottas briefly lifted the throttle through the slight bend on the run towards Turn 15, just as he had done on previous laps, the Cadillac immediately began losing speed.
When Valtteri Bottas returned to full throttle, the car almost immediately entered super-clipping again, losing approximately 60 km/h before the braking zone.
“On the same lap I locked the front at Turn 1 and went long,” Valtteri Bottas explained. “Then I think the systems got a little confused because of the extra distance. I had massive super-clipping into Turn 15 and, when I pressed the brake, only the fronts were working [which is why he locked up almost immediately, ed.], as if I was no longer recovering energy at the rear. Something got confused there.”
McLaren encountered a similar issue after Turn 1 incidents
Something similar, although with different consequences, also happened to both McLaren cars after their respective excursions at Turn 1.
In those cases, however, the MCL40 control unit remapped the energy system by simply removing electrical deployment on the straight leading towards the braking zone for Turn 4 on both cars. That prevented further anomalies from developing during the remainder of the lap.
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