Power solution of long-life IoT devices application

With the rapid development of IoT technology, the IoT devices require a variety of power solutions based on different applications.

These power solutions are the same for applications using Bluetooth, LoRA, Narrowband and WiFi technologies:

a. background current: 0.5~10 μA
b. send information current: 10~500 mA
c. wide temperature range, from -20O to +60O, sometimes -40~85O
d. Excepted lifetime: 1~10 years
e. Operating voltage: 1.9~3.0V
f. high safety
g. High power density.

Lithium-manganese dioxide batteries (Li/MnO2) exhibit high energy density, no passivation, high power, low self-discharge, wide operating temperature and low cost, Which makes it particularly suitable as an IOT power solution.

How to evaluate Li/MnO2 battery for long-life IoT devices power supply solution

Evaluating the life span and suitability of Li/Mn02 batteries can be determined via the following test items: As shown in Figure 1 below, the working temperature of CR17450AH can cover a range between -40~85OC. Even operating at a temperature of -40 OC, the battery is capable of operating at approximately 75% capacity, the batteries possess ~75% capability even at -40°C, ensuring efficient operation in different regions and different climates.

In all long-life application products, a low self-discharge rate is an important feature. The micro-calorimeter method demonstrates the heat flow of the CR17450 is 1.895μW at 25°C, the corresponding self-discharge current is 0.586μA, and the corresponding annual self-discharge rate is 0.2% (Figure 2). The low self-discharge rate is therefore ideal to meet the long-life requirements of IOT applications.

Figure 1: CR17450AH discharge with 560ohm load at different temperature.
Figure 2: Self-discharge with Micro-calorimeter
Table 2: EVE long-life Li/MnO2 products
Note: CR2/3AL and CR17450L are semi-sealed products ( -40o to +70o). CR17335AH, CR17450AH and CR17500AH are fully sealed products (temperature range, from -40o
to +85o) for harsh environments.

Figure 3 and Figure 4 show good environmental tolerance. The voltage, CCV (Load: 450mA,0.5s) and internal resistance remains stable during storage at 60°C with 1Mohm background load. After being stored at 60°C for 200 days (simulated 10-year life), EVE’s CR17450AH battery has no corrosion and no leakage, and the capacity remains at 2482~2512mAh compared to 2637~2682mAh for a new battery. Capacity retention is above 95% even after 85°C 90% R.H. for 1000h.

Figure 3: The storage performance with 1Mohm load at 60OC.
Figure 4: Capacity change after 85O 90%R.H.

In addition, the discharge curve of the Li/MnO2 battery indicates that voltage changes with the change of capacity.

When the capacity is insufficient or an unexpected fault occurs, the voltage will drop to a certain value and the remaining capacity will be used for a fault indication.

A fully automatic production line together with various inspection equipment (SEM, GC-MS, BET, ICP, and UL1642 and IEC60086 testing equipment etc.) can guarantee product quality.

For the application of IoT devices, EVE has developed a series of industrial Li/ MnO2 batteries and the products are
shown in Table 2.

Conclusion

The long-life Li/MnO2 battery provides high pulse capacity, a wide temperature range, long life, low self-discharge and residual capacity that can be monitored making it suitable for a wide range of IoT applications.
The long-life Li/MnO2 battery has been successfully used in several applications, including independent smoke alarms,
NB-smoke alarms, smart gas meters and smart electric meters for more than seven years.

About the author

Oliver Qiu holds a master’s degree in materials science and engineering. He joined EVE as a technical engineer at the lithium primary battery technical center in 2019.

About the company

EVE’s core business focus includes lithium primary batteries, lithium-ion batteries, power systems, etc. and offers product solutions to support smart grids, intelligent transportation, smart security, energy storage, new energy
vehicles, etc. which are adapted to a variety of specialised industries.