Kill switch on a racing machine: why it's mandatory
The kill switch is the switch that allows you to instantly cut power to the motors. On a racing machine, it's mandatory for a simple reason: if the throttle gets stuck, if the controller malfunctions, or if the rider loses control, it must be possible to immediately stop the propulsion, without searching for anything. On an electric scooter, where the torque is delivered instantly, this safety feature is even more critical. Here's what the regulations require, and how to install it correctly.
The essentials
- At E'trott Racing, a red kill switch is mandatory and must be mounted on the handlebars, accessible without releasing the grips.
- It should only cut power to the motors; it should not brake or lock the wheels.
- It should not be confused with the power switch, which isolates the battery and is useful in the workshop, pit area, and during transport.
- He tests it before each session, performing a wheelie.
Why it is essential
An electric scooter never stalls. If the throttle gets stuck, if its cable is damaged, or if the controller receives an incorrect signal, the motor will continue to propel the scooter forward. This is further compounded by racing situations: a rider falling while the scooter continues moving on its own, a collision between two scooters, or a lever getting caught in a rider's clothing.
The kill switch provides a simple and effective solution to all these situations: a red button, always in the same location, that cuts off the motor power. The rider doesn't have to think, and track marshals know exactly where to act if they need to intervene on a vehicle.
Here's what the E'trott Racing regulations state:
The regulations for the 2026 French E-Trott Racing Championship, as defined by the FFM (Fédération Française du Motocyclisme), are quite specific:
- The scooter must be equipped with a functioning, red circuit breaker switch or button;
- It must be operable by the rider without having to let go of the handlebars, on either side, within easy reach, easily accessible, and clearly visible;
- Its sole function is to cut off power to the motors;
- Under no circumstances should it activate the brakes or lock the wheels, so that the scooter can continue moving forward by inertia in a safe manner.
The same regulation also requires that the motors automatically stop as soon as the acceleration command is released. Therefore, the circuit breaker is a second layer of safety, and not the only one.
Why not brake? Because locking the wheels at high speed causes a fall. Cutting power allows the machine to slow down in free-wheel mode, under the rider's control, who can still use their mechanical brakes.
Pilot kill switch and battery isolator: two functions
| Driver cutoff | Battery insulator | |
|---|---|---|
| Where? | At the handlebars | On the power line, near the battery |
| When | While riding, in case of a problem | At a standstill: workshop, pit area, transportation |
| What it cuts through | Powering the motors | Harness the full power of the battery |
| E-scooter Requirement | Mandatory, red, and do not let go of the handlebars | Practical and recommended |
The battery isolator cuts power to the entire system: it's the best protection against accidental starts while you're working on it, or during transport. Our racing circuit breaker serves this purpose: it cuts the battery power line and is sized for the currents of our custom builds. We install it on all of our racing machines.
Most common assembly errors
- A button that is out of reach: This button, located on the deck or under the column, is unusable while riding and will fail the technical inspection.
- A button that brakes: Connected to the "brake" input of the controller, it can trigger a sudden electric braking. Regulations prohibit this.
- Fragile wiring: Thin wires that run through the column and can be cut when the scooter is folded or when turning the handlebars.
- An undersized switch on the power line: it overheats, wears out, and can potentially weld itself in the closed position.
- Improper Reconnection: Quickly connecting the power line to the controller's capacitors can cause a spark that damages the contacts. Our guide on pre-charging and spark prevention explains how to avoid this.
The choice of cables and connectors for the power line follows the same rules as the rest of the system; see our guide on power cables and connectors.
Assembly in the workshop
Connecting a kill switch depends on the controller: some have a dedicated input for cutting off motor commands, while others require specific wiring. If you are unsure about the wiring diagram, have it installed professionally: we can install it as part of our installation package, or for an hourly rate with our labor service.
Pre-session testing
- The scooter is on its stand, with the drive wheel raised.
- Gently accelerate: the wheel turns.
- Activating the circuit breaker without releasing the handlebars: the wheel must stop being driven and continue to rotate freely, without being braked.
- Restart the system and verify that the machine restarts normally, without any sudden jolts.
Workshop tip
Practice finding the emergency shut-off switch without looking, while stationary and then while riding slowly. The day you need it, you won't have time to search for it. And in the pit area, always disconnect the battery before placing any tools on the machine.
Frequently Asked Questions
Is a kill switch useful outside of competitive settings?
Yes. On a powerful machine, it provides protection in case of a stuck throttle, and the battery isolator prevents accidental starts in the workshop and during transport.
Does the brake contact alone not suffice to cut off the motor?
Brake contacts cut off the acceleration when braking, but they depend on the controller and their wiring. The E-scooter regulations require a separate, red, and easily accessible device that cuts off the motors without engaging the brakes. This device must be reachable without releasing the handlebars.
Does the button necessarily have to be red?
For the E'trott Racing championship, yes: the 2026 regulations require a red, clearly visible switch or button so that both riders and officials can immediately identify it.
What does the technical inspection check?
Make sure the kill switch is present, red, easily accessible without letting go of the handlebars, and that it is functional. Our guide "Preparing an electric scooter for the track" lists the other points that should be checked.