As Internet-of-Things (IoT) technology reduces form factor and power consumption, many new battery-powered applications have become possible. For example, the wireless readings from remotely located ‘smart-agriculture’ soil moisture sensors are helping farmers to increase yields and make their farms more environmentally friendly. In sprawling storage facilities, wireless sensors send periodic temperature measurements, helping warehouse operators maintain operating conditions suitable for the types of goods being stored there. While these innovations are valuable, the very feature enabling their operation is also their biggest shortcoming – battery power. Without it, locating sensors at geographically remote locations would be impossible because no alternative fixed power source is typically available and installing one would be prohibitively expensive. In this blog, we show how IoT device operation can harm battery capacity before presenting a pioneering IC Nexperia has developed to boost battery life, so they need replacing much less often.
Pulsed operation pulls down battery voltage
Environmental variables like temperature, pressure and humidity typically change very slowly, so they don’t require measuring very often – perhaps only once every few hours. Similarly, many security cameras only need to capture and transmit a video signal if they detect movement at the location they are monitoring. Therefore, these devices can spend most of their working life on standby or sleep mode, only waking periodically to record and transmit a reading or video stream. In addition, long periods in sleep mode help conserve power (consuming only a few microamps), and they can operate off Lithium primary coin cell batteries (like CR2032) or lithium thionyl chloride (like LS14250) for several years. Non-rechargeable lithium primary batteries have high energy density and long shelf life.
Sleep mode is not an issue for lithium primary batteries. However, the infrequent periodic short bursts of activity (pulsed mode) when the device’s microcontroller, sensor and wireless radio (LoRa, Wi-Fi, Zigbee) are all fully powered up is problematic. Lasting only a few milliseconds, these bursts consume 10s to 100s of milliamps, significantly straining a coin cell battery. Coin cell manufacturers rate these product lifetimes for relatively low standard current draws (<1-3 mA). Extended use in this brief, high-current pulsed mode is detrimental to overall cell capacity (lifetime) while simultaneously causing a significant drop in voltage during heavy loading—potentially making it too low for the application it is powering.
Intelligent battery booster IC maintains a constant voltage level
Nexperia’s NBM7100A/B and NBM5100A/B are revolutionary new battery management ICs that can extend the life of a typical Lithium coin cell battery by up to an order of magnitude (10x) while increasing the peak output current available to a pulse load by up to 25x. These ICs contain two high-efficiency DC/DC conversion stages and an intelligent learning algorithm. The first conversion stage transfers energy from the battery to a capacitive storage element at a low rate. The second stage utilizes the stored energy to provide a regulated (programmable from 1.8 V to 3.6 V) high pulse (up to 200 mA) current output. The intelligent learning algorithm monitors the energy used during repetitive load pulse cycles and optimizes first-stage DC-DC conversion to minimize the residual charge in the storage capacitor. When not performing an energy conversion cycle (standby state), these devices consume less than 50 nA.
Brownout protection inhibits storage capacitor charging cycles when the battery voltage is low near the end of life and the battery’s chemical recovery time is longer. A ‘low battery’ indicator alerts the system when the battery reaches its functional endpoint. A serial interface is included for configuration and control by a system microcontroller: I2C in "A" versions and SPI in "B" versions. Besides current loading, temperature extremes adversely affect battery performance and lifetime. The NBM devices operate over a wide operating temperature range (-40 °C to 85 °C), making them equally suitable for indoor and harsh outdoor industrial applications where environmental conditions are unpredictable. The NBM5100A/ and NBM7100A/B, with their novel two-stage energy management approach, intelligent learning algorithm, and low standby current, help extend battery lifetime in wireless IoT applications while reducing maintenance costs associated with battery replacements.
Added environmental benefits
Extended operating lifetime will also significantly reduce the amount of battery waste in low-power Internet of Things (IoT) and other portable applications (like key fobs) while making small coin cells a viable power source for applications that could previously only operate from AA or AAA-type batteries.
To learn more about Nexperia’s Battery Life Booster ICs, visit the product page here.