The best and recommended way to power beacons of indoor positioning system is to have a fixed external power supply.
Our converters and chargers support ~110V and ~220V. External power supplies give a peace of mind and freedom to focus on other aspects of the system.
However, if the fixed power supply is not feasible, there are different battery options available. There are even more exotic options, like solar panels, that could be useful in some special applications as well.
First of all, notice that we don’t discuss powering of modems. Modems are nearly always active. They typically don’t sleep. In the majority of cases they are even computer connected. Thus, powering them is typically not an issue: either they are USB connected and powered via USB, for example, Modem v5.1; or the power is easily available via ~220V to +12V converter for the Super-Modem.
Stationary beacons (anchors) have fixed locations. At a first glance one may think that to provide the power to them is not a problem and the main focus shall be on the mobile beacons. Thus, there are claims of 1 year, 3 year, 5 year battery lifetime for tags in UWB or BLE systems…
But in the reality, it is opposite in the majority of cases:
Therefore, it is important to very clearly understand that powering of mobile beacons (tags) is typically not a problem. But powering of stationary beacons could be due to the cost or limitations of wiring or size and costs of required batteries and associated battery replacement/utilization and recharging costs.
Like the majority of other modern electronic devices, Marvelmind beacons sleep most of the time. They wake for a very short time, do the job, and go to sleep immediately in order to save energy.
Beacons have a duty cycle with highly irregular power consumption: some milliseconds of relatively high current during the active phase are followed by tens or hundreds of milliseconds of nearly zero current during the sleep phase. The difference in current consumption between the modes is 1000:1 or even more.
Typical power consumption pattern:
As a conclusion:
As discussed above, the beacons sleep most of the time. Thus, it is possible to calculate a required energy for a single location update. By knowing that energy and by knowing the battery capacity, it is possible to calculate the number of location updates the battery can provide before it will depleted.
As it can be seen, the difference is drastic.
In reality, the difference is less dramatic, because there is a current in sleep mode as well, which is not zero after all. Thus, if the sleep time is long, the sleep current starts notably contributing to the total power consumption. For a 1-year battery lifetime, the sleep current consumption may prevail over the active current consumption.
External fixed power supply is the best and most reliable choice.
External DC-DC power converters is the best and most reliable choice for mobile beacons:
In many cases, an external USB power supply is available and you can simply connect a micro-USB connector to the beacon and get both power and the data stream to and from, for example, Raspberry Pi or nVidia Jetson.
Similar can be done with Industrial beacon or modem, if external +12V (+6V…+15V) available from the onboard sources of the mobile vehicle/drone/robot.
The majority of Marvelmind devices have internal LiPol battery. Typically, it is a 3.6V cell. For example:
Some devices have additional external batteries, for example, Headlight: it has 2 larger-capacity external LiPol cells that extend the capacity of the internal battery by the factor of 3-5 – depending on the chosen external cells.
Other devices, like robots, have massive internal batteries – up to 96Wh for Boxie and expandable; and 740Wh and expandable for Robot v100. Those batteries supply the motors, electronics and the beacons on board of the robots.
Industrial beacons intentionally don’t have internal batteries:
USB power banks are the simplest and the most straightforward way to expand the battery lifetime of Super-Beacons or other USB powered beacons. Notice the following though:
External Battery-12V-5Ah-Outdoor is the simplest battery supply option for Industrial beacons. With default settings and 8Hz update rate it provides about 2 weeks of autonomy (depending on the mode and size of a submap). With different settings and with slower update rate, it can last for a year, if needed.
For those he really need batteries, we are offering customized external LiPol batteries. Then can be literally any capacity, voltage and and size. You need a 1 year battery lifetime – not a problem! 5years? – not a problem either.
Though possible, it is rather difficult to calculate mathematically an expected battery lifetime because:
Besides, pure mathematical calculations live too much room for uncertainty and a design to measure in practice in order to prove the validity of the results
It is possible to measure the current consumption of each element of a cycle and integrate. It is possible, but difficult still not very reliable, because:
The best option in practice is to measure the real battery lifetime and extrapolate it keeping in mind underlying physics:
There are many affecting factors on the battery lifetime. The most affecting – the location update rate – already covered earlier. What else: