The power management on the MiX 4000 and MiX 6000 units is driven by its configuration as well as additional built-in firmware control functions that are not user configurable.
User configurable power management
User configurable power management is grouped into two categories, unit power management and peripheral power management. Configuring the unit's power management profile correctly is vital as it impacts vehicle battery power consumption as well as the unit's battery and all associated peripherals.
The FM units have a UP (Unit Power) line and PD (Positive Drive) line on the Mobile device template. On the MiX 4000 and MiX 6000 these are configured under the Unit power management and Peripheral power management settings on the Mobile device connected to the template.
Unit Power Management
The unit power management settings on the mobile device template controls the power management functionality of the mobile device.
These settings impact the mobile device as a whole and it is important to note that once the device has been turned off or shut down with these settings, all other power related setting will no longer take effect. In other words, switching the mobile device off with these settings also switches off all peripheral devices and stops any further peripheral surfacing from happening.
Remember that unit power management logical device settings are available on the MiX 4000 and MiX 6000 mobile devices.
Click here for more information on these settings.
Peripheral power management
The Peripheral power management section controls the power management functionality of all peripheral devices connected to the unit. These settings define the required out of trip behavior of the onboard modules (such as the GSM modem, Bluetooth and GPS) as well as externally connected peripheral hardware.
The peripheral power management logical device is available on the MiX 4000 and MiX 6000 mobile devices.
Click here to learn more about the peripheral power management settings.
Firmware controlled power management
The firmware will generally follow the power management config requested by the user. It however also makes some independent decisions based on the internal battery state of charge, the need to send high priority event messages and the need to periodically check into the central commissioning server.
Managing the internal battery
The firmware has a responsibility to maintain the state of charge and state of health of the internal battery in the mobile device, if one is fitted. It will certainly prevent any damage being caused due to overcharging/discharging or charging/discharging outside of safe temperature limits. In some cases, this may result in the mobile device shutting down before it has been asked to do so by the config.
The various charging modes of the internal battery are also under firmware control. Charging will typically take place while the mobile device is in trip but there may also be situation where the internal battery is charged for a limited period of time while the vehicle is parked. In this case the measured current being drawn from the vehicle’s battery may be higher than expected. This behavior should not be of concern as the mobile device is continuously monitoring the vehicle’s battery and will not continue charging its internal battery if this is likely to have an adverse effect on the vehicle’s battery.
Power mode boost surfacing to send important events
There are certain events that need to be sent even if the mobile device has been powered down. These are any events that are configured in the device's Event template config to be sent as active messages with a priority of Critical (limited), Critical or Emergency.
When these events become true the firmware will initiate its own surfacing event that is independent of any user configured power setting. This process will attempt to ensure that this message is sent, usually by any means available to the mobile device.
NOTE: Be aware that by configuring events with such high priorities (Critical and Emergency), other configured thresholds could be overridden. For example, the daily satellite message limit will be exceeded if necessary or the lower vehicle battery voltage limit, configured under unit power management - Turn device off when battery voltage fall below, will be ignored.
Be aware that configuring such high priority events should only be done if this is absolutely necessary. This configuration could result in unexpected satellite data costs or this could completely deplete the battery of a vehicle parked up for an extended time.
Power boost surfacing for commissioning server check-in
Every time the unit restarts or at least every 24 hours the firmware will initiate a power boost mode surfacing in order for the unit to complete its check in with the central global commissioning server. This is to enable it to do a basic health check as well as determine if there are new commissioning settings that need to be updated. Its primary objective during this process is to make that commissioning connection but once this is done it may also have time to send any normal or urgent priority messages that have may been queued.
This mechanism can explain why there are occasionally out of trip position updates for an asset visible on MiX Fleet Manager long after its last trip when its configured surfacing and device shutdown intervals have already elapsed. This will occur from time to time but is not a reliable mechanism to ensure out of trip AVLs will get sent. If out of trip AVLs are a requirement, then the correct surfacing interval and unit power management settings should be set in the mobile device config as outlined above.
LED behavior
The behavior of the mobile device LEDs when an asset is out of trip are often a cause for some confusion and concern. These devices don’t really have a power mode where they are totally off, unless they are being shipped from the factory. Once powered up for the first time there is likely to always be some LED activity as long as the mobile device remains powered. This is true even after the shutdown mobile device time has elapsed.
Typically, in this mode only the green (GPS/GNSS or position) LED will flash and only for a short time every minute. The LED activity is related to the device’s internal wake up cycle. Once a minute it will wake up to take care of some internal activities and during this time the green LED will flash a few times indicating that the asset is out of trip without any position fix. At this point it has no position fix because the internal GPS module is powered down under these conditions and the unit is in a super power saving mode called stop mode.
This behavior is completely normal and does not indicate that the mobile device is not obeying its unit power management config or that it will be draining the vehicle’s battery.
What the LEDs will also show is when a firmware power boost or config initiated surfacing is taking place. When this happens the green (GPS/GNSS or position) LED will ramp up to the 3D fix state.
The red (modem or comms) LED will be seen establishing a network connection and end in the state where it is connected to the network and able to communicate.
Once the power boost or surfacing is complete the internal modules will be shut down again and the green LED will return to its previous behavior.