What is boost mode, how do you use it and what is it for?

To power up, to push, to increase… these are just some of the meanings of the word “boost”. A term you’ll recognise from many areas: video games, electric chargers or even household appliances. And now, increasingly, in electric cars, especially when it comes to announcing their specifications. But what does “boost mode” really mean, how does it work and what is it for?

In fact, the term “boost” applied to a vehicle has been used for a long time, and it is not exclusive to electric cars. It refers to an operating mode or a specific programme that allows more thrust to be delivered or the available power to be increased, but only momentarily. For example, in many cars with supercharged combustion engines, the “boost” function, also known as “overboost”, acts on the turbocharger’s wastegate to allow greater boost pressure when maximum power is demanded, that is, when accelerating flat out.

It is also very common to refer to the boost function in plug-in hybrids (or in some mild-hybrid models) when the electric motor works as support for the combustion engine in order to improve response. And in electric cars, as you have probably guessed, “boost” mode is the one in which the propulsion system delivers its maximum power, something that is achieved “simply” through programming or software.

If you have followed any Formula E race you will remember “Fan Boost”, which allowed the drivers who could activate it (they are chosen by public vote before the races) to have extra thrust for a few seconds at a moment of their choosing during the race; or Attack Mode, which amounts to the same thing: drivers pass through a designated zone to activate a mode in their electric single-seaters that gives them extra power for a few laps.

More power and better performance, but for a limited time

In every case it is a momentary contribution of power or thrust, and there is an explanation for it: to avoid damage to the components of the combustion engine or the propulsion system. For this reason, in electric cars this “boost” mode is only activated when you accelerate flat out and is maintained continuously for a few seconds, but it would deactivate if you could keep accelerating for longer. These are not programmes to be used frequently in daily driving, but rather a “helping hand” to achieve maximum acceleration on a one-off basis, for example during an overtaking manoeuvre.

This is the reason why many electric cars announce a power and torque figure, but specify separately the maximum power that can be reached in boost mode. One example: the Audi RS e-tron GT announces a maximum power of 440 kW (598 CV), which is what its two electric motors and the battery system can deliver continuously, while in “boost” mode the power rises to 475 kW (646 CV), which cuts the 0 to 100 km/h acceleration time from 3.6 to 3.3 seconds.

Specifically, in electric cars, boost mode involves a very large extra consumption of electrical energy, and also significant stress on the battery, which can limit its service life. This is the reason why some brands such as Fisker in the Fisker Ocean SUV have decided to limit the number of times you can activate boost mode to 500, with an indicator in the corresponding menu on the infotainment system screen in which a countdown shows how many activations you have left. A strategy that is, after all, a protective measure against the additional wear that activating boost mode entails… or a way of doing business, since customers could extend this limit through a software update.