Lithium battery PCB and BMS

The core components of lithium batteries include the battery cell and PCB (usually is BMS in power batteries). The battery cell, as the “heart” of the lithium battery, is responsible for storing and converting energy; while the PCB or BMS, similar to the “brain” of the lithium battery, is responsible for monitoring and controlling the state of the battery.

Lithium battery PCB (printed circuit board) can play a role in charging and discharging protection for series-parallel battery packs, and at the same time, it can detect over-voltage, over-current, over-temperature, under-voltage, and short-circuit state of each single battery in the battery pack, extend the service life of the battery, and avoid damage to the battery due to over-discharge. Lithium battery PCB is an indispensable part of the lithium battery.

Lithium battery PCB also has equalization protection, there are two ways of energy-consuming and energy transfer.

Energy-consuming equalization refers to a battery with high power or voltage in a string of batteries, with a resistor to dissipate the excess power. Energy-consuming equalization is divided into charging time equalization, voltage fixed-point equalization and static automatic equalization.

Equalization during charging: When the voltage of any battery is higher than the average voltage of all batteries during charging, the PCB will start equalization protection.

Voltage fixed-point equalization: the lithium battery PCB is fixed at a voltage point to start equalization, only at the end of the battery charging, equalization time is shorter.

Static automatic equalization: carried out in the process of charging or discharging, even if the battery is in a static resting state, when the voltage is not consistent, lithium battery PCB will start equalization protection until the voltage remains consistent.

Transfer type is to allow large-capacity batteries to transfer to small-capacity batteries in the form of energy storage to detect the capacity of the battery to do equalization, divided into capacity time equalization and capacity fixed-point equalization.

BMS(Battery Management System)

Battery management system, referred to as BMS, has the function of measuring battery voltage, and also includes battery protection function, battery equalization function, battery reserve function, energy measurement function, network communication function, etc. BMS can prevent over-discharge of the battery. The BMS prevents abnormal conditions such as over-discharge, over-charge, and over-temperature of the battery.

The BMS measures the current and voltage in the battery cells and sends this information to the application that will determine the state of the battery, called the state of charge or SOC.These measurements also help the application to determine the state of health (SOH) and the remaining useful life (RUL) of the battery by calculating the battery’s actual maximum capacity (which decreases over time). It will estimate whether the battery is still working or needs to be replaced, and allows for other optimizations. For example, by determining the SOC and SOH of each battery cell, the BMS can balance its charging and discharging to ensure even wear and tear, resulting in longer battery life and more performance.

One safety aspect of the BMS is a feature that many designers tend to overlook. The accuracy of the system will allow it to perform, but it will also determine if the battery is suffering from over- and under-voltage, or if the system is experiencing overheating or overcurrent. For example, in the event of a collision, an electric vehicle must figure out that the battery is no longer within typical specifications and must initiate a shutdown or the damage could be catastrophic.

Since lithium batteries’ performance may damage in severe overcharging and over-discharging states, and even create a risk of explosion, BMS exist to monitor, protect, and manage lithium batteries in a balanced manner, thereby improving their efficiency.

Both lithium battery PCB and BMS play a protective role for lithium batteries. The difference between them is:

1. The lithium battery PCB is composed of IC, MOS tube and resistor and capacitor components. BMS can be edited and comes with battery management software, relatively more intelligent, equivalent to the brain of the lithium battery, play a control role.

2. Lithium battery PCB have an important role in the field of 3C lithium batteries and power batteries, BMS are used in the field of power batteries.

3. The BMS is better operated than the battery PCB, but the performance is not stable in low temperature.