Universal BMS and monitoring its real time SOH estimation to predict the battery life

Project Title

Universal BMS and monitoring its real time SOH estimation to predict the battery life

Project Area of Specialization Electrical/Electronic EngineeringProject Summary

The project is about a Battery Management System(BMS)  that can monitor and control the voltage, current, and temperature of a battery pack. This management system can also detect the charging capacity(State of Charge) and also predict the life span of the battery. The battery pack consists of cells connected in series or parallel or maybe both. In this project, the 13 Li-ion cells are connected in series, but we expect to develop a Universal BMS that can manage 20 cells connected in sequence. Universal BMS is a BMS that can monitor any number of cells connected in any sequence. The cells in the universal BMS are balanced intelligently in the sense that whether the cell is of any type of batteries used in daily life. This would be done through the complex algorithms programmed in BMS IC. 

Project Objectives

The purpose of the project is to implement an intelligent Universal BMS that can manage any type of rechargeable battery using the voltages, current, temperature, and internal resistance of each individual cell connected to the battery pack so that it can operate in a safe zone for a longer period of time more efficiently.

Project Implementation Method

To design the intelligent Universal BMS, each and every cell in a battery pack has to be monitored in real-time. The battery parameters that have to be monitored include voltage, current, internal resistance, and temperature. Therefore, the techniques to get these parameters to be monitored are as follows:

VOLTAGE READING CIRCUIT

The circuit developed to read the voltage of a cell is called the Subtractor Circuit. The Subtractor also called a difference amplifier, uses both the inverting and non-inverting inputs to produce an output signal which is the difference between the two input voltages V1 and V2 allowing one signal to be subtracted from another. More inputs can be added to be subtracted if required.

To detect the voltage, TL-084 Amplifier IC is used.

CURRENT SENSING CIRCUIT

A current sensing circuit or board monitors electronic current flow in a number of applications. Current sensors are able to monitor the current by measuring the drop in voltage for a resistor, which is placed in the direct path of the current.

Measuring the current of each cell is done by using shunt resistance and load resistance across each cell. Shunt resistance is always used in a series of load resistance. Load resistance is 5 ohm and the shunt resistance value is set to 0.05 ohm. 

CELL BALANCING CIRCUIT

The technique which is used in the project to balance the cells of the battery pack is Passive Cell Balancing. This method uses a resistor to dissipate the energy of the cell with the highest voltage in a series pack. Generally, the weakest cell reaches the maximum voltage threshold faster for the same current through the rest of the other cells in the pack. When the cell voltage exceeds the SOA (safe operational area), the switch is turned on and the cell is allowed to discharge through the resistor also called the bleeding resistor, so that the cell voltage and SOC come down to a safe level. This process is repeated until all the cells have reached the same voltage.

MULTIPLEXING & ARDUINO UNO

In this project, Arduino Uno is used as A/D Converter and for multiplexing, 8:1 multiplexer 4051 is used. This multiplexer is used to select from 8 analog inputs. There are three S0, S1, and S2 pins, which by giving appropriate values, one of the analog inputs is set as the output on the Z pin.

The voltage of each cell present in the battery pack is monitored using a voltage monitoring circuit. As the battery pack is of higher voltage therefore to convert the voltage from analog to digital using Arduino Uno, a multiplexer needs to be interfaced in between the voltage sensing circuit and Arduino Uno as shown in the figure below:

The above-discussed implementation methods are firstly done on different software including Proteus, multisim, orcade, and EasyEDA. Then, implemented on hardware. There is also a software model that includes sending data on the cloud using UART or CANbus protocols. 

Benefits of the Project

As this is an intelligent Universal BMS and is able to monitor any type of rechargeable battery, it can be used with different electronic appliances that use batteries to operate, including UPSs, EVs, laptops, mobiles, emergency lights and fans, and many more. It can effectively manage the whole battery pack to make it work smoothly for a longer period of time. In order to save the monitored data, the displayed data will also be sent to the cloud so that it can be used for further analysis of the type of cells connected in a battery pack.

Technical Details of Final Deliverable

Initially, ADC is used for displaying the monitored data then for real-time monitoring CAN-bus or UART protocols will be used.

(Already mentioned in the Project implementation method)

Other than that temperature, internal resistance, State of Charge (SOC), and State of Health (SOH) of the battery will also be monitored. 

For temperature, a thermistor will be used with each cell while for internal resistance, SOC and SOH complex algorithms will going to be implemented.

Final Deliverable of the Project HW/SW integrated systemCore Industry Energy Other Industries Transportation , Security Core Technology Big DataOther Technologies Artificial Intelligence(AI), Cloud InfrastructureSustainable Development Goals Affordable and Clean Energy, Decent Work and Economic Growth, Industry, Innovation and Infrastructure, Climate ActionRequired Resources

Item Name	Type	No. of Units	Per Unit Cost (in Rs)	Total (in Rs)
			Total in (Rs)	20710
PCB	Equipment	5	2000	10000
Battery Spot Welding	Miscellaneous	1	2000	2000
Controller	Equipment	1	2000	2000
ICs	Equipment	10	50	500
UART/CAN-bus	Equipment	2	200	400
Resistors, Capacitors	Equipment	60	3	180
Transistors	Equipment	13	10	130
BMS IC	Equipment	3	1500	4500
Modules(i.e. Node MCU)	Equipment	1	1000	1000