M3 Charging

Charging the sensor

The M3 sensor charges via the USB-C port on the back of the sensor. Remove the sensor from its magnetic mounting plate first to access the port; the button and charging indicators are also on the back.

Connection type	USB-C cable
Full charge time	Approximately 2–5 hours from empty
Fastest charging	Use a charger with at least 12.5 W output (2.5A at 5V). A standard phone charger works fine; higher wattage chargers won’t speed things up further.
Maximum battery life	Up to one year between charges under optimal conditions; with power-hungry features such as smoking detection and crowd detect disabled
Typical battery life	Several months for a typical installation with standard features enabled. Features like smoking detection, crowd detect, and Instantly Turn On Alarm accelerate battery drain.

Charge before going to the property. New sensors can sometimes not be fully charged. Charge the sensor at home before installation.

Charging indicator lights

The charging indicator lights are on the back of the sensor, visible after removing it from the mounting plate.

Blinking lights
Sensor is currently charging. Lights pulse while power is flowing from the USB-C cable.
Solid lights
Sensor is fully charged. Safe to unplug and install.
No light
No power reaching the sensor; check the cable and charger. Try a different USB-C cable.

For the full LED reference covering the front status light, see LED indicator lights - M3 sensor.

Running the sensor hardwired

If you prefer not to rely on battery power, the M3 sensor can be left permanently connected to a USB-C charger. This works well for long-term installations where charging the sensor between stays is inconvenient.

Indoor only	Hardwiring is supported for indoor mode only. Sensors installed in outdoor mode should not be permanently wired; the USB-C port in outdoor mode is oriented for rain protection, not continuous cable connection.
AC Power Adapter	For a permanent, cable-managed installation, Minut offers an AC Power Adapter that connects via the sensor’s USB-C port and wires into a standard wall socket.
Battery protection	When left plugged in for extended periods, the sensor automatically enters battery protection mode.

M3 Battery

Battery protection mode

When the M3 sensor is left connected to the charger for an extended period, or is hardwired, it automatically switches to battery protection mode. In this mode, the battery is held at a slightly lower charge level than full capacity. This is intentional and prevents long-term battery degradation from continuous charging.

What you notice	The charging indicator lights may appear not to show a full charge even though the cable is connected. The battery level in the app may show slightly below 100%.
Is it a problem?	No. This is expected behaviour. The sensor continues to work normally and monitoring is not affected.
To exit protection mode	Unplug the sensor for more than 24 hours. The protection mode will deactivate and the battery will charge to full on the next charge cycle.

If the sensor is hardwired and you see the battery level sitting at 80–90% in the app rather than 100%, this is battery protection mode working as designed. No action is needed.

Low battery notifications

Minut sends a low battery notification when the sensor’s battery drops to around 15%. To avoid a false positive from a one-off reading, the notification is only sent after the sensor has reported the low level several times in a row.

Notification type	Push notification and email to the organisation owner and all team members with access to the rental unit
Trigger level	Around 15% battery remaining
How long until empty?	In battery-optimal conditions (standard features, normal use), the sensor continues to work for approximately 2–4 weeks after the low battery alert. Features like smoking detection and crowd detect reduce this window.

Extending battery life

If battery life is shorter than expected, disabling the following features will extend it significantly. Each can be toggled in your Noise Preset settings or device settings.

More Frequent Sensor Updates: disabled by default. When enabled, the sensor syncs data to the app more often, increasing radio activity and battery drain. Disable if battery life is a priority.
Crowd Detect: continuously monitors the number of devices near the sensor. Disabling it reduces battery consumption noticeably, especially in busy areas.
Instantly Turn On Alarm: when enabled, the security alarm activates without a countdown delay, requiring the sensor to update motion detection more frequently. Disabling it restores the default hourly motion update cycle and extends battery life. This does not affect how quickly the alarm triggers once motion is detected; that always happens instantly.
Notifications for Alarm Recognition: disabling glass break and noise-based alarm recognition reduces sensor processing load and improves battery life.

Outdoor installations drain the battery faster. The outdoor AudioID noise filtering system runs continuously to prevent false alerts from wind, which uses more power than indoor mode.

Replacing a low battery sensor

If you manage multiple properties, the most efficient way to handle a low battery sensor is Sensor Swap; it lets you replace a depleted sensor with a fully charged one without reinstalling. All settings, thresholds, and historical data transfer automatically to the replacement sensor.

See Sensor Swap.

Sensor not charging

If the charging indicator lights don’t appear when you plug in the sensor, try the following before contacting support:

Try a different USB-C cable: a faulty or low-quality cable is the most common cause
Try a different wall charger or USB port
Check the USB-C port on the sensor for debris or damage; use a dry, soft brush to gently clean it if needed
If the battery is completely flat, leave the sensor plugged in for 10–15 minutes before checking the indicator lights; a fully depleted battery takes a few minutes before it shows any charging signal

If none of the above resolves the issue, contact the Minut support team.

Email hello@minut.com with the following information: