Lithium-ion cells are being widely used in smart devices due to their compact and lightweight nature, and also their up to the mark performance. Thanks to these batteries, for now, people can stay assured that their devices will serve them for one full day or even a couple, on a single charge. These batteries, however, also have a certain lifespan, which can drastically decrease if the battery is not used with care.
Over-charging a battery can lead to a shorter life span while the battery can get heated, catch fire, or even explode. Even over-discharging a battery has its own adverse effects on the health of the battery. The battery should be allowed to discharge only to a certain safe level, which is approximately 5% below its full capacity. Also, the temperature of the battery should never become too high or else it will lead to disturbing the normal functioning of the battery. With all these (actually a lot more) things to take care of, it becomes almost impossible for the users to monitor and manage these conditions manually. This is where the advanced battery thermal management systems come into play.
Battery management systems are intelligent circuits loaded with some MOSFETs, ICs, and sensors which are dedicated to monitor and manage the various aspects of a battery. They prevent the batteries from leaving the safe zone of function by preventing over-charging, over-discharging, overheating, and other such issues. They also record and output important information like the amount of battery power remaining, the expected battery life, battery performance, and so on, to the user.
A modern battery management system generally administers the following battery parameters:
1. Voltage- The battery management system incorporates two switching MOSFETs. One to prevent over-charging and another to prevent over-discharging. When the voltage of the cells reaches a certain threshold level, the charging MOSFET breaks the circuit, thereby stopping further charging. Similarly, when the voltage level drops below a certain minimum potential threshold, the discharging MOSFET breaks the discharging circuit, thus preventing further discharge.
2. Current- The charging and discharging currents are maintained within the safe limits, preventing damage.
3. Temperature- The thermal conditions of the battery are monitored by the thermal management system. The cooling systems are triggered accordingly, keeping the temperature from rising above the safe temperature limits.
4. State of power- State of power is the measure of power that is left and the time period which it will last for as per the instantaneous voltage, current, and thermal conditions.
5. State of charge- The state of charge of individual cells is the amount of charge stored in them. The battery management system ensures that a balance maintained between the charge of individual cells or else the individual cells may undergo stress.
