stevesingo wrote:I can't see why they would harvest (outside of MGU-H) at WOT, it would be wasteful of fuel in the extreme.
How would they know when to harvest under WOT conditions, certain SOC, certain road speed, certain time at WOT?
ERS is usually deplete at the end of straights, and therefore harvesting is needed to ensure there is electrical power to accelerate out of the corner right after. This is especially true for a track like Bahrain where a long straight is followed by a major acceleration zone. The ERS may not be able to harvest enough energy under braking alone to ensure enough electrical energy for the acceleration right after, and therefore some harvesting is done just before the braking. That is the reason for the flashing red light, which is to inform the driver behind that the car is harvesting and might slow down even though its driver is not braking.
As for how they know when to harvest, I imagine each team has complicated maps tailored for each circuit on where to harvest and where to use the energy. They do this so they can get away with the smallest and lightest Energy Store as they can, so they end up not having to store excess energy and save weight. Those batteries are heavy.