High or low blood glucose levels in the human body can lead to serious health risks, so monitoring blood glucose levels is a top priority. With 150 million people worldwide suffering from diabetes, there is a huge demand for personal portable blood glucose monitors (BGMs).

A dynamic glucose monitor (CGM), which helps diabetic patients check their blood glucose readings in real time and also monitors blood glucose values over an extremely long period of time, can continuously monitor blood glucose levels and then alert users when their blood glucose levels reach danger levels.

This sensor unit uses coin cells or coin batteries that are connected to the body for a certain period of time (e.g., 8 to 10 days). The aggregator unit is a battery-powered handheld unit that can read blood glucose data using radio frequency (RF) technology such as near-field communication. The battery management subsystem of the aggregator unit consists of a battery charger, battery meter and protector. 3.7 V lithium-ion single battery is sufficient to run a typical aggregator unit. It can be charged via the USB or DC input of the power adapter.

The battery gauge predicts and estimates the remaining capacity, state of charge, time to depletion, and operating conditions of the battery under different load states, thus helping to solve the challenges in battery management. With smart battery meters, users can extend runtime  and battery cycle life. Texas Instruments' (TI) Impedance Track™ measurement algorithm enables battery capacity prediction with greater than 99% accuracy, giving it superior analog measurement performance and battery feature modeling capabilities.

Offering a variety of single battery measurement options, this blood glucose monitor is not only compact and cost effective, but also has ultra-low power consumption. The meter can be housed in a battery pack or on a system PCB, the latter being more commonly found in portable medical applications.

System PCB-based power meters, such as the BQ27426, require minimal user configuration and consume very little current during normal operation. For higher levels of integration, some meters have integrated detection resistors, such as the BQ27421-G1.

On the other hand, if the meter is carried in a battery pack, a solution with high accuracy can be provided by flash-based firmware and an integrated 256-bit secure hash algorithm such as the BQ27Z561-R1. Protection ICs such as the BQ2970 provide voltage, current and reverse charger protection.

Battery level meters increase the level of sophistication and intelligence in power management. Systems that do not have accurate power meters can only be shut down at a fixed voltage. Many devices shut down with a system voltage of 3.5 V to protect the spare capacity used for worst-case scenarios (reserved power for shutdown), but as shown in Figure 4, measuring only the battery voltage through a microcontroller and analog-to-digital converter, which in turn generates a low battery level warning, is not a reliable way to measure remaining power. This is due to the fact that most applications have variable loads. The battery meter will calculate the remaining charge and change the shutdown voltage to meet the required reserve capacity requirement for any condition, thereby increasing the runtime.

In addition to the advantage of retaining reserve capacity, some battery power meters are also able to not report a 0% state of charge due to the high transient pulse loads generated by the application, thus dropping the battery voltage below the terminal voltage. This feature is advantageous when the battery still has a high charge, but the high transient load can cause the termination voltage to be reached early.

Batteries are complex electrochemical systems that are affected by cell aging, temperature and impedance. Algorithms, compact devices and advanced device integration are all key features to improve system performance.