The Internet of Things is a constantly evolving area. New generations of smart devices necessitating higher pulse currents, together with the advent of low powered networks, are changing the game and placing new demands –and opportunities!– on batteries.
A good example of these evolutions is new smarter meters. They are making additional demands on their autonomous power supplies including higher power pulse capability and a wider operating temperature range, while long lifetime and ATEX compliance remain mandatory.
Two main trends in the smart/connected devices market are particularly instrumental in the development of batteries capable of sustaining high pulse currents while still ensuring a long lifetime:
Saft is constantly investing in research and development in order to address complex IoT designers’ needs. On top of the two ranges of battery technologies available for high pulse applications, spiral Li-SOCl2 (LS) and Li-MnO2 (LM), Saft is now launching a brand new range of batteries, the LSP range, to best match your use case.
Most smart meters to date have been using Lithium Thionyl Chloride (Li-SOCl2) cells. Li-SOCl2 chemistry exhibits the highest nominal voltage among primary battery chemistries (3.6 V) and the spiral construction of the cells are particularly adapted for applications requiring very high pulses. They have an exceptional reputation for reliability and long life in smart metering applications, with hundreds of millions of cells successfully deployed worldwide.
But an important aspect of Li-SOCl2 cells is the passivation process that causes the formation of a Lithium Chloride layer on the anode. This is a major challenge for pulsing applications: a high pulse current will cause the voltage to drop for a few milliseconds, and should the voltage drop below the system cut-off voltage, it could jeopardize the operation of the smart meter. This phenomenon is particularly strong in warmer places as the heat, especially above + 40°C, promotes passivation and with Smart meters being deployed in warmer regions such as the Middle East and Asia, we had to find solutions. We’ve therefore optimized our Li-SOCl2 cells’ voltage response over the years, not to completely eliminate passivation, which is impossible, but to control, anticipate and take it into account when sizing a battery for a particular application. However, when the application cut-off voltage is above 2.8 V, the risk of reaching this threshold is high, which leads us to recommend our customers to use a capacitor or supercapacitor, in order to stay on the safe side.
An alternative solution made available by the introduction of low-consumption electronic components, is Saft’s LM range of Li-MnO2 cells which have been developed specifically for metering applications. This chemistry’s lower nominal voltage (3 V against 3.6 V for Li-SOCl2) had always presented a barrier as it was close to the cut-off voltage (normally 2.5 V to 2.8 V) for metering electronics.
In ‘sleep’ mode, 99% of the time, the meter’s main power consumption comes from the microprocessor. This can be reduced by decreasing the operating voltage of the microprocessor, which has helped the adoption of Li-MnO2. Now, the system cut-off voltage can be as low as 1.8 V.
In ‘active’ mode the meter actively transmits data, requiring both high power and high voltage and additionally the use of a DC-DC converter is required. Since, for a given power requirement, the lower the voltage and the higher the current, this is a good match with Li-MnO2 technology with its high power capability and absence of passivation.
In a nutshell, the cells are optimized to retain all the lifetime benefits of Li-SOCl2 cells in a robust, hermetically sealed, low self-discharge design capable of offering up to 20 years of service.
With the new LM cells, it was possible to offer both high capacity (up to 3 Ah for A size) and high power capability (up to 2 A at 20°C for A sizes) at operating temperatures between - 40°C to + 85°C, but for applications with low temperatures and cut-off voltage above 2.4 V, Li-MnO2 wasn’t an option…
Saft’s new range of primary solutions –the LSP– combines reliable, low self-discharge Li-SOCl2 cell technology in parallel with a state-of-the art and carefully selected LiC (Lithium-ion Capacitor).
The LiC selected by Saft is showing the lowest self-discharge and ESR (Equivalent Series Resistance) at most temperatures and one of the highest measured capacitance during a pulse, ensuring that the LSP range will meet the lifetime of 10 years or more required by the new generation of connected devices. Saft also thoroughly tested a wide range of EDLCs and LiCs to ensure the best compromise between pulse sustaining capability, operating temperature range, and performance stability over lifetime. Eventually, the difference of the LSP consists in optimizing the combination of an Li-SOCl2 cell with an LiC supported by Saft’s proprietary sizing and lifetime calculation model.
Manufacturing lines with a high level of automation and a particular attention to the process and production tools of our solutions enables us to offer high volume production to the highest quality standards. Additionally, we offer a complete range of solutions that comply with international standards for intrinsic safety for use in potentially explosive atmospheres (ATEX).
With this new range of LSP batteries, Saft is now, more than ever, able to answer most of the challenges met by IoT designers.
The graphic below compares the specificities and main advantages of each of our battery ranges.