Your BAP tags need to offer the best performance in terms of read range or communication with sensors but… what about optimizing battery life?
BAP tags (Battery Assisted Passive) can provide longer read ranges than full passive RFID tags. They can also allow for extra features such as data logging of sensors for later data transfer to RFID readers.
If you are developing your own BAP tags, you know enough to look at the power consumption of the RFID chip you are using. No wonder, on top of the external devices you are using for your application – sensors, actuators, microcontrollers, etc. – you also need to take into account the power consumption of the RFID IC itself.
There’s two main ways of looking at a BAP design:
- The RFID chip starts consuming power as soon as the battery is connected to the tag.
- The RFID chip includes a battery switch so you command that switch to connect and disconnect the battery whenever you want.
Battery switch in RFID ICs thought for BAP tags
A good RFID chip that allows for BAP features needs to include a good battery switch.
You’ll see the point very easily. Imagine an application where your customer wants to use your BAP tags for cold chain data logging.
You have designed a great product: great communication with RFID readers, very good sensor performance and multiple options for alerts and configurations.
Tests on transportation of different items such as blood bags or pharmaceutical products have been positive so you’re really eager to take your product to the market.
However, once you start manufacturing in volume, you notice a problem. Your customers may not be using your BAP tags as soon as you ship them but they store your products to be used when needed. For some customers this is taking long – 3 months, 6 months… – and once they start using them, they notice that the battery life is a lot shorter than what you guarantee.
Well, you manufactured your product, connected the battery and guaranteed let’s say 9 months of data logging with a specific configuration. However, your product, even if not activated, may have been consuming energy from the battery while in storage.
Battery switch characteristics
An RFID chip without battery switch will consume your batteries really fast. Period.
An RFID chip with battery switch will save some energy. The key is to understand how much energy it will save.
Battery switches have three objectives:
- When the battery is not connected, you need to minimize the amount of power going from the battery to the chip. This will never be zero but should be the lowest possible if you want to improve the design of your BAP tags.
- When your product has run out of battery, you may still want to read the information stored in the memory. You cannot log more data but you can of course communicate without batteries.
Well, this is only true if the battery switch of the RFID chip prevents the power harvested from the RF field going into the battery. Remember the battery is connected even though it’s empty so you could actually be wasting part of the energy in that direction.
- You need to minimize the voltage drop in the switch. That’s for clear energy saving reasons.
Selecting the right RFID chip for your IoT solution requires more than just checking its sensitivity or communication protocols. Make sure you have the battery switch in mind if you’re thinking on developing BAP tags.