Battery Module Design-Definition, Design, and Composition

On Present-day, due to the increase in electric operated machines and equipment’s, people interest in lithium-ion batteries, the power source EV’s is also growing. However, it so happens that we get confused by specific terminologies used for different kinds of batteries. We know it by names like battery cell, battery module, and battery pack. Commonly used name is a battery; the three words mentioned above actually refers to the different types of batteries.

To operate on an electric vehicle require an enormous power of thousands of times stronger battery that just a small phone battery. That is why EVs need from dozens of battery cells up to as many as thousands. The composition thus of electric vehicle battery might slightly depend on the type of electric vehicle being used. But in general, EV battery composes of the cell, module, and a pack.

Classification of an electric vehicle battery

1.Battery cell

The basic unit of the lithium-ion battery that exerts electric energy by charging and discharging. Each of these cells is made up of cathode, anode, and electrolyte into a rectangular aluminum case.

2.Battery module

A battery assembly put into one frame by combining a fixed number of cells to protect the cell from any external shocks, heat, and vibrations.

3.Battery Pack

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The final shape of the battery system installed in an electric vehicle of electric equipment. Composed of modules and various control protection systems including battery management system, a cooling system, etc.

So in large battery packs, the battery cells are arranged in modules to achieve the serviceable unit. Battery cell production is different than a battery pack or module. Battery cell production is primarily a chemical process, whereas module and pack production is just assembling of a cell by mechanically assembly process. The pack contains battery cells, software (battery management system), and often a cooling and heating system, depending on where and how the battery pack is to be used.

A battery management system is an electronic system that manages a module and packs to ensure that battery operates within its intended design parameters. These parameters are different, like the voltage, current, temperature, state of charge, and state of health. The BMS is responsible for measuring, calculating, storing, and communicating this battery characteristic as and when needed.

How do you design a battery module with high power?

The battery cell is of fixed voltage and capacities. Capacity varies but the voltage does not. To meet power specifications, a battery pack may need to be used. The type of battery, the number of cells in it, the shape of the pack, and the component of the pack will be determined by the voltage and load current of the device.

Configuration of battery packs

• Linear or F-type

• Cubic or composite F-type, Multi-row cells
  

• Nested type cells

• Circular type cells

• Linear or L-Type cells
  

Above are the different arrangements of the cell in a battery module for a particular type of specification or need.

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Module assembly

Solder or weld – most batteries are a spot that is welded using nickel strip for contacts. Direct soldiering to the cell can be a dangerous process. It is easily melted or the safety vent can be disturbed or it can also be the cause of internal shortening if the heat is high. This damage is also not noticeable until later. So generally, there is a capacitive discharge spot welder that allows the end-user to solder the custom packs together without any fear of damage to the battery in quite a easy way.

Heat shrinks tubing – It is the most familiar way to hold pack and make a module is by heat-shrink tubing method. It has enough strength for the small packs but if there is increased weight, we will be needing more structural strength. This is possible by adding fish paper or plastic sheet to the structure. Then this pack is assembled in modules by putting it into a system box or plastic case.

Battery Holder – If you are designing or using the battery holders than you must ensure that there is sufficient provision for long or even short cells or wide cells. Make sure to keep the clip edges sharp and far away from touching the cell, as this can cause short between the cell held by the same clip.

The?battery pack?of a high voltage system is formulated to control the power flow?of battery to and from the battery cells and works for maintaining the power level in the designed envelope.

1.Contactors

Electrically triggered switches which are chiefly used to separate the?pack of the battery?of the high voltage system in the case of the non-usage of automobiles are called contactors. However, these are helpful for security purposes and they can be unfastened to separate the pack of batteryif the malfunction occurs in any segment of the automobile, and the pack of battery is forced out of its designed envelope.

2.Precharge circuit

As soon as the pack?of battery closes the transitions and contactors from a state of disconnected to a state of connection, a possibility arises for the substantial currents that are momentary. Thus, the changein it should be a controlled and authorized process. It also provides the current that regulates and controls the precharge circuit and includes a resistor and a contactor that is additional but controls the flow of current.

3.Fuse

The fuse is a prominent device used in the purpose of maintaining security. The fuse protects apparatuses from passing the excess current that includes the flowing current surpassing the contactors, thus protecting it from damage. The selection of fuse is not unimportant and should be harmonized with the other componentsof a high voltage system in a manner that all the failure modes, necessary for functioning are either covered by the contactors or the fuse.

4.Manual service disconnect:

It’s considered as the fourth safety method that is helpful in a high voltage?battery module?and is termed as MSD abbreviated as “Manual Service Disconnect. It’s used for producing the hindrance in the continuity of electricity within the pack. It isa touch-safe and removable enclosure that encompasses the fuse.

5.HVIL

It is the final yet important safety mechanism that is helpful in packs of high voltage and is known as the HVIL. It is an electrical circuit with continuity that intersects the access points of high-voltage such that itsignals and informs the system of battery management in the case of opening access points.

Module battery testing involves charge and discharge tests to ensure that the cell connections are secure enough and also strong sufficient to manage anticipated current loads without weakening, failing, and overheating. Addition test should be there to ensure the cell is balanced, voltage reported accurately, and temperature sensor functions appropriately.