Preparing a Slack Core 920R: What the workshop did, and why

Our custom-built "Core" electric scooter is one of the most refined machines to come out of our workshop: 30,000W of power, a top speed of over 150 km/h, and electronics integrated into the chassis rather than simply attached to it. This guide outlines the steps we took, in order, and, most importantly, *why* we made those choices. Because a build like this isn't just about a large battery; every component was selected to ensure that everything works together harmoniously.

The machine, in numbers:

According to the page "Slack Core Preparation" by Rage Mechanics:

The battery: the source of everything

Our Performance 80V 40.5Ah battery for Slack Core 920R is the most powerful battery in our catalog for this machine. Its specifications are as follows: 80V nominal voltage, consisting of 22 cells in series, 40.5Ah capacity for a total of 3240Wh, Molicel P45B cells, and a BMS (Battery Management System) connected via Bluetooth with balancing and protection features.

Here's why we made this choice: The product sheet summarizes the two main reasons very well:

• Higher voltage provides more speed for the same motor;
• More available current allows for the actual delivery of the set power, without any drop in power when going uphill or cut-offs.

This battery is not compatible with a standard 920R: it requires controllers designed for this voltage, and a compatible charger. Our guide on upgrading to a higher voltage explains what this change entails for the entire system.

The controllers: integrated, not added

On many custom builds, controllers often end up being mounted externally due to a lack of space. On the Slack, the C350 controllers are integrated into the frame using a plate and housing specifically designed for this model. This integration offers three key advantages: the controllers are protected, they dissipate heat through a designated surface, and the wiring remains short and tidy.

Around, our 3D-printed parts for the Slack Core 920R, made from PETG, complete the integration: covers, supports, and cable guides for the controllers, the SmartDisplay, and the Performance battery. Our guide on 3D printing scooter parts explains what these parts can handle and what they cannot.

Braking: Proportional to speed

At speeds exceeding 150 km/h, braking is the primary safety component. The Slack is equipped with Hope Tech 4 V4 brakes, featuring four-piston calipers, paired with 160 mm Brake Stuff rotors. These 3 mm thick reinforced rotors are no longer manufactured, as the brand ceased operations in 2025; we now offer the E-Watts 160 mm reinforced rotor (3 mm) as a replacement. Our guide on braking for a powerful electric scooter details these choices.

Control: Understanding what's happening

A 30,000W machine is being monitored. The SmartDisplay shows essential data and records telemetry, allowing for analysis of each ride. Temperature sensors have been added to the motors: they allow you to track their heating and protect the machine when it's being pushed to its limits. A motor that overheats loses performance and can be damaged; knowing this in real-time changes the way you ride.

Charging

One last detail, although it's not a major one: an improved charging port, designed to recharge the battery more quickly given its capacity. The charger, of course, must be compatible with the voltage of the new battery.

The order of operations

If we were to repeat this preparation process on another Slack (likely referring to a specific type of electric scooter or component), the order would be as follows:

1. Before increasing the power output, always check the brakes and rotors
2. control of steering and rolling components;
3. Battery and controllers, selected together;
4. Integration, wiring, temperature sensors;
5. Display, telemetry, and settings, on the track, step-by-step.

And what about the law?

A machine of this caliber is designed for track use and private property. On public roads, electric scooters are limited to a speed of 25 km/h.