the max boost mode only runs for like 30 seconds then shuts off on my v11.

Diagnosis

The behavior you are experiencing is a built-in thermal and voltage protection mechanism. The Dyson V11 Torque Drive is engineered with a sophisticated Battery Management System (BMS) that monitors the temperature of the lithium-ion cells and the digital motor in real-time. When you engage "Boost" mode, the motor draws maximum current, which generates an exponential increase in heat within the battery pack and the motor housing. If the internal sensors detect that the temperature has reached a critical threshold—or if the battery voltage drops too rapidly under the heavy load—the BMS triggers an automatic shutdown to prevent permanent cell degradation or motor burnout. This is not a mechanical failure but a safety feature. You can confirm this is the cause if the vacuum shuts off abruptly but will restart after 2-5 minutes of cooling, or if the LCD screen displays a "Filter" or "Airway Blocked" message immediately following the shutdown, as restricted airflow forces the motor to work harder and heat up faster.

How to Fix It

Since this is a design specification, you cannot "disable" the timer, but you can optimize the vacuum's performance to extend the duration of Boost mode by reducing thermal stress. Follow these steps to maximize your runtime:

1. Deep Clean the Filter: Remove the purple filter assembly from the top of the cyclone. Wash it under cold running water until the water runs clear, ensuring you rinse the pleated folds thoroughly. Shake it out and leave it to air dry for a full 24 hours. A damp or partially clogged filter restricts airflow, causing the motor to overheat and trigger the Boost shutdown much faster.
2. Clear the Torque Drive Head: Flip the cleaner head over and remove the brush bar by twisting the end cap. Use scissors to cut away any hair or string wrapped around the brush. A jammed brush bar creates mechanical resistance, forcing the motor to draw more current and heat up the battery.
3. Check the Inlet Valve: Inspect the "wand" (the long tube) and the inlet where the wand connects to the main body. Use a flashlight to ensure no coins, pebbles, or clumps of debris are lodged in the throat. Even a partial blockage increases the vacuum's internal temperature.
4. Strategic Mode Switching: Instead of starting in Boost, use "Auto" mode. The V11 uses an acoustic sensor to detect debris levels and will automatically ramp up power. This manages the battery temperature more efficiently than manually locking it into Boost mode.

If That Didn't Work

If the vacuum shuts off in under 30 seconds even after a deep clean, or if it shuts off in "Eco" or "Auto" mode, try these advanced troubleshooting steps:

• Perform a Hard Reset: Remove the battery pack entirely by unscrewing the three Phillips-head screws (one at the rear of the handle and two at the base of the battery). Leave the battery disconnected for 10 minutes to discharge the capacitors on the PCB, then re-seat the battery and tighten the screws firmly. This can sometimes clear "ghost" error codes in the BMS.
• Inspect for "Pulsing" Behavior: If the vacuum doesn't just shut off, but "pulses" (starts and stops rapidly) before dying, this is a definitive sign of a blockage. Check the bin inlet and the cyclone shroud for a blockage that is too deep to see with a flashlight; use a broom handle to gently push through the wand to ensure a clear path.
• Battery Cell Degradation: If the vacuum is more than 2-3 years old, the internal resistance of the battery cells may have increased. When the high current of Boost mode is requested, the voltage "sags" below the minimum operating threshold, triggering an immediate shut-off. In this case, the battery pack (Part No. 968522-02 or equivalent) needs replacement.
• Check for Thermal Throttling: Feel the battery casing immediately after a shutdown. If it is hot to the touch, the issue is thermal. Ensure you aren't charging the vacuum immediately after a heavy Boost session; let it cool for 15 minutes before plugging it into the wall charger to preserve cell longevity.

Heads Up

• Avoid "Boost Cycling": Do not repeatedly trigger the trigger switch immediately after a Boost shutdown. This can force the vacuum into a "Critical Thermal Lockout," where it will refuse to power on in any mode for up to 30 minutes.
• Filter Drying: Never put the filter back in while it is even slightly damp. This creates a massive airflow restriction that will trigger the Boost shut-off almost instantly and can lead to permanent motor damage.
• Charging Habits: To extend the life of your V11 battery, avoid leaving it on the charger 24/7 if you only use Eco mode; however, for heavy Boost users, keeping it topped up ensures the voltage remains stable.
• Storage Temperature: Do not store your vacuum in a freezing garage or a hot shed. Extreme temperatures calibrate the BMS incorrectly, leading to premature shutdowns in high-power modes.