Project 1 Mechanical design of battery pack

An electric battery is a source of electric power consisting of one or more electrochemical cells with external connections for powering electrical devices.

When a battery is supplying power, its positive terminal is the cathode and its negative terminal is the anode. The terminal marked negative is the source of electrons that will flow through an external electric circuit to the positive terminal. When a battery is connected to an external electric load, a redox reaction converts high-energy reactants to lower-energy products, and the free-energy difference is delivered to the external circuit as electrical energy.^[3] Historically the term "battery" specifically referred to a device composed of multiple cells; however, the usage has evolved to include devices composed of a single cell. Primary (single-use or "disposable") batteries are used once and discarded, as the electrode materials are irreversibly changed during discharge; a common example is the alkaline battery used for flashlights and a multitude of portable electronic devices. Secondary (rechargeable) batteries can be discharged and recharged multiple times using an applied electric current; the original composition of the electrodes can be restored by reverse current. Examples include the lead-acid batteries used in vehicles and lithium-ion batteries used for portable electronics such as laptops and mobile phones.

Battery Pack:-

A battery pack is a set of any number of (preferably) identical batteries or individual battery cells. They may be configured in a series, parallel or a mixture of both to deliver the desired voltage, capacity, or power density. The term battery pack is often used in reference to cordless tools, radio-controlled hobby toys, and battery electric vehicles.

Cell: ANR26650M1-B

Mechenical Connection :
Design mechanical interconnects to prevent accidental short circuits. Size these mechanical interconnects to carry the expected maximum rated current for both the maximum time and ambient temperature in which the pack is expected to operate.

Cell Interconnects :
Size cell interconnects for the expected maximum current carrying capability. Improperly sized tabs could heat up excessively, resulting in even higher resistivity. For reliable welded connections at the terminals, Al23 Systems recommends either pure nickel tabs or nickel-clad copper tabs. In addition, other alloys afford both the weldability, strength and low resistance, which are all desirable features of a good interconnection. Cell interconnects (tabs) should be neither soldered on the end caps nor attached using extreme heat. 4123 Systems recommends tabs be resistance or laser-welded to both ends of the cells. Resistance welding provides a constant current for a specified period of time through a salient feature in the weld tab. These parameters can be specified and regulated for a consistent high-quality weld every time.

The Gap Between Each Cell :

The cell vents, located on the end cap(s) of the cells (on the POSITIVE side of the cell), should not be blocked by any mechanical means. Blocking the cell vent and then sufficiently abusing the cell so as to build up pressure in the cell prevents the cell from properly venting. An ESS designed to install cells end-to-end needs at least 1 mm of space between the cells to allow the vent to open under fault conditions.

Series Strings:

Cells combined in series strings can achieve higher operating voltages by connecting the positive terminal of one cell to the negative terminal of the next cell. Connect strings of series cells using their current collection tabs in a manner similar to that illustrate

Parallel Strings :

Cells combined in parallel strings can achieve higher operating capacities by connecting like-polarity terminals of adjacent cells to each other. Connect strings of parallel cells using their current collection tabs in a manner similar to that illustrate

we Using Cyclindrical cell :

Cylindrical cells are the most common cell type in use today. This design allows for better automation processes and techniques that increase consistency and lower cost. Compared to prismatic cells, cylindrical cells can be produced much faster so more KWh per cell can be produced every day equaling lower $ per KWh. The electrodes in a cylindrical cell are wound tightly and encased in a metal casing, This minimizes electrode material from breaking up from the mechanical vibrations, thermal cycling from charging and discharging and mechanical expansion of the current conductors inside from thermal cycling. Many cells are combined in series and in parallel to increase voltage and capacity of the battery pack. If one cell goes bad, the impact on the entire pack is low. With prismatic cells if one cell goes bad it can compromise the whole battery pack. Cylindrical cells radiate heat and control temperature more easily than prismatic cells.

Here we are using lego connectors to connect the multi no of cells into one pack or construct the battery pack.

In lego connectors mostly used in the battery pack construction is because it's very easy to repair or dismandle the cells from the battery pack.

Nickel strip is generally used in battery building. Its due to its efficiency of usage in spot welding and soldering as well its high corrosion resistance over time. It has good properties and excellent resistance to many corrosive environments. The pure nickel will never get rust after it applied to battery packs.