We sometimes get asked if it’s possible that smartphones can detect beacons without Bluetooth being on. All beacons are based on Bluetooth LE that, in turn, relies on Bluetooth being switched on in the phone to scan for beacons. There’s no magic underling operating system mechanism on iOS nor Android that allows you to use Bluetooth without the user having Bluetooth on.
More users are leaving their Bluetooth on due to the proliferation of connecting with other devices such as cars, Bluetooth headphones and smart speakers. If you are writing an app you should take steps to detect if Bluetooth is on and prompt the user appropriately.
The phone and beacon industries need to better educate users that Bluetooth is no longer the heavy battery drainer it was in the early days of smartphones.
After project rollout, human effort used in regularly replacing batteries can be significant and the human resource cost of doing so can dwarf the actual cost of the beacons. Hence, unless it’s a temporary scenario it’s best to specify beacons with as large a battery capacity as possible. Beacons with smaller capacity batteries are only suitable for short trials, temporary events or use during development.
While BeaconZone stocks a very large range of beacons, we purposely haven’t stocked any beacons with batteries smaller than CR2032 because the battery life of CR2025 and CR2016 beacons is usually too short. All our beacons use either CR2032, CR2450, CR2477 or AA batteries.
Battery capacity is measured in mAh. The mA part (without the h) is the unit of current. As an example, a CR2477 battery typically has a capacity of 1000 mAh which means it can supply 1 mA for 1000 hours or, for example, 2mA for 500 hours. However, most beacons only use tens or hundreds of µA when transmitting, where 1 µA is 1000 times smaller than a 1 mA. Also Bluetooth beacons only transmit for a few milliseconds (1 ms = 1/1000 sec) at a time so you can see how a coin battery can last a long time.
Here are the main battery sizes and their typical mAh rating:
CR2032 = 250 mAh CR2450 = 500 mAh CR2477 = 1000 mAh 2 x AA = 2200mAh (Alkaline), 3000 mAh (Li) 4 x AA = 4400mAh (Alkaline) or 6000 mAh (Li)
A beacon such as the SmartBeacon-AA containing 4 Lithium batteries can last 6x one with a CR2477 battery and 24x one with a CR2032 battery. This gives a battery life of up to 7 years depending on other configuration parameters.
Lithium AA batteries such as the Duracell Ultra Lithium and Energizer Ultimate don’t just last longer than Alkaline AA batteries. Their voltage also doesn’t vary so much with temperature which might be a consideration if your rollout is outdoors.
One of the issues with using Bluetooth beacons is that it’s not easy to predict how long batteries are going to last. Battery life depends not just on the battery capacity but also the transmitted power, advertising interval, beacon processor chip type and whether the beacon has timed transmission. Also, beacons vary from model to model, sometimes even between revisions of the same model. In some scenarios it’s essential to know which beacon models are the most power efficient and how long batteries will last.
Over the years we have spent a considerable amount of time investigating actual battery use. It’s not as simple as you might think. You can’t use an ammeter because it can’t see the short pulses in peak power. The majority of the power is expended in very short, few millisecond (ms) transmit pulses, in between which the beacon goes into low power sleep.
Nordic Bluetooth Advertising Power Use
Testing needs to integrate the current used over multiple advertising periods. The test equipment needs to capture this data at sub 1ms precision in order to catch the pulses. The testing also needs to be flexible enough to work for advertising periods from 100ms to 10 sec.
We have custom in-house designed test equipment capable of real-time battery current testing. This enables us to compare different manufacturers’ beacons having the same configured settings and provide our consultancy clients with beacon battery use data based on their exact configuration settings.
As an example, an interesting test we did was was to compare the Sensoro AA transmitting just iBeacon vs iBeacon at the same time as the 3x Eddystone advertising packets. With only ibeacon @ 760ms, 0dBm advertising, 4 typical alkaline batteries would last 7.7 years. Transmitting all 4 iBeacon and Eddystone frames reduces the battery life to 2.9 years.
Another interesting observation has been that the beacons that have the strongest signals aren’t necessarily the ones using the most battery power. Design of aspects, such as the antenna, contribute to power efficiency.
Too many potential customers contact us asking what’s the least expensive beacon that provides the best range, the best battery life and the smallest size. Unfortunately, all these things are related. You need a larger battery to provide enough power for a longer range. A large battery implies a larger beacon size. A larger battery and case implies a more expensive beacon. The choice of ‘best’ beacon usually involves some sort of compromise.
It’s also often the case that customers focus on price, range, battery life and size without considering other factors such as:
Visual appearance – Good-looking beacons can sometimes be counter-productive as they can be attractive to thieves.
App – Some manufacturer configuration apps are easier to use than others.
Waterproofing – Some unexpected scenarios need waterproofing due to high humidity.
Motion triggering – Some beacons provide motion triggering to significantly increase battery life.
On-off button – It’s sometimes desirable to be able to turn the beacon on and off without having to remove the battery.
Attachment options – Some beacons include strong double sided stickers, tabs for screws or holes for fastening.
We often get asked what’s the best iBeacon? Unfortunately, there is no one best beacon for all scenarios. It depends on your particular project and business requirements. Having said this we have some favourites based on specific characteristics:
Best for Price: FSC-BP103 – Inexpensive beacon that transmits up to 10 channels simultaneously:
Best for Features:M52-SA Plus – Large easy replaceable battery, long range, temperature, humidity, accelerometer:
Best for Battery Life:SmartBeacon-AA Pro – Allows use of 4x AA batteries. Use lithium AA batteries for 7+ year battery life (also depends on settings).
Best for Setup App:Minew range – Minew’s latest BeaconPlus range (those supporting both iBeacon and Eddystone) provides the best in class app.
It explains that while a battery has a fixed initial capacity, how you draw current from the battery affects how much of that capacity you get to use. At a relatively low constant current of 0.5mA you get most of the capacity while at 3mA you only get 60%.
For Bluetooth LE the current isn’t usually constant. Instead, it advertises at up to 7mA, for of the order of a milliseconds followed by a pre-set inter-advertising period between 100ms and 10 secs. This gives the battery time to recover.
The article explains how Bluetooth LE firmware should be designed to not turn everything on at initial startup so as to not stress the Battery unduly. It also mentions how it’s also wise to test the battery in the actual situation rather than relying on the battery mAh rating to calculate expected battery life.
Most beacons can transmit more than one type of advertising , for example iBeacon, Eddystone and sensor data. In practice, no beacon can send more than one kind of data simultaneously. Instead, they send the different data sequentially, one transmission very shortly, milliseconds, after the other. Many manufacturers describe this as sending data in different channels which shouldn’t be confused with different Bluetooth LE frequency channels used to reduce the affects of wireless interference.
Some devices such as Minew and Sato can send 6 channels that can include iBeacon, Eddystone UID, Eddystone URL, Eddystone TLM, sensor, acceleration and device info:
Transmitting one type of data takes of the order of 1 millisecond (ms) every configurable 100ms to 10secs period. It’s during the sending that the majority of the battery power is used with the beacon sleeping between transmissions. The following oscilloscope trace shows the battery power used, over time, with one channel:
Care should be taken to configure only those types of data that are required. If you configure more than one channel then there’s a corresponding, almost linear, increase in use of battery power for every extra channel.
We take a beacon the same as yours, or one you send to us, and measure the actual power use with your specific settings.
Note, however, that if you will be using batteries that have been included with beacons, those batteries will have been used for an indeterminate time in the factory for soak testing the beacon. You will need to use new batteries to obtain the maximum battery life.
Nordic Semiconductor, the manufacturer of the System on a Chip (SoC) in most beacons has a useful online calculator that helps work out the battery current used when advertising or when connected.
You need to set the SoC chip type (see the specification for the beacon you are using), voltage (3v as it’s usually a coin cell), DCDC (usually off), clock (usually external) and tx payload (set to 31 bytes). You can then vary the role (advertising or connected), power and advertising interval to see the affect on the battery current.
Dividing the battery capacity by the current will gives the approximate battery life. The resultant battery life calculation will be a very rough approximation and will be less if the manufacturer has added extra circuitry such as sensors. The online calculator is best used to get an appreciation of how changing parameters or the SoC type affects battery life rather than being a definitive value. For more accurate battery use it’s necessary to measure the actual battery current.
We mentioned Wiliot last March and since then their R&D team has created early engineering samples that prove it’s possible to create a battery-less Bluetooth LE beacon harvesting energy from radio frequencies (RF).
The Wiliot device looks more like a RFID tag than a traditional beacon in that it’s supplied as a very thin PVC inlay sheet containing the chip and wire antenna together. The thin form factor, no battery and the relatively low cost will allow it to be manufactured into or stuck onto clothing and packaging that will provide for many new usecases.
Producing such a device isn’t easy as it can’t use existing System On a Chip (SoC) devices as produced by Nordic, Dialog and Texas Instruments (TI) because they are too large and use too much power. Wiliot has had to create their own SoC from the ground up, including software tools to develop and program the devices. We have been told it will be a year before Wilot has all the components in place for commercial rollout. Meanwhile, selected organisations can join the Early Advantage Program (EAP). There’s a new a product overview (PDF below) that explains the EAP and the main usecases, connected packaging, connected apparel, logistics and asset tracking:
Wiliot already have Early Advantage Program (EAP) agreements in place with over a dozen brands including top fashion brands, a telco, appliance companies, a furniture brand and packaging companies.