Project 1 Mechanical design of battery pack
what is a cell
A cell is a single unit device which converts chemical energy into electric energy. A battery usually consists of group of cells. Depending on the types of electrolytes used, a cell is either reserve, wet or dry types.
what is battery
Batteries are a collection of one or more cells whose chemical reactions create a flow of electrons in a circuit. All batteries are made up of three basic components: an anode (the '-' side), a cathode (the '+' side), and some kind of electrolyte (a substance that chemically reacts with the anode and cathode).When the anode and cathode of a battery is connected to a circuit, a chemical reaction takes place between the anode and the electrolyte. This reaction causes electrons to flow through the circuit and back into the cathode where another chemical reaction takes place. When the material in the cathode or anode is consumed or no longer able to be used in the reaction, the battery is unable to produce electricity. At that point, your battery is "dead."
what is a battery pack
A battery pack is a set of any number of (preferably) identical batterys 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 vechicles .
Components of battery packs include the individual batteries or cells, and the interconnects which provide electrical conductivity between them. Rechargeable battery packs often contain a temperature sensor, which the battery charger uses to detect the end of charging. Interconnects are also found in batteries as they are the part which connects each cell, though batteries are most often only arranged in series strings.
CALCULATIONS
According to the objective we should calculate the capacity of 18KWH
the cell ANR2665M1-B data sheet
Energy or capacity calculated
power*time
power (p)=voltage (v)*current (i)
3.3*2.5=8.25kw
to get 18kwh we are assuming 48s 48p
48*48=2304cells
series connection gives =48*3.3=158.54
parellel connection gives =48*2.5=120a
from this we can get
158.4120=19.008kw
DESIGN OVERVIEW
Abattery pack is a system of multiple comoponents and functions and its design involces the application of knowledge and pratice in the electrochemical ,electrical,mechanical ,thermodynamic and control fields . the following sections summarize the various stages of battery pack design covering specific aspects of the cells A123 cells which may be unique
from other cells
1.the first step in the design of the pack is to determine the configureartion of cells how many cells overall how many are in the series and how many are in parellel this is the foundation
of the design process since all other design decisions follow from the cell configuration
2.the second step is to design a mechanical structure around the cells to support and protect them . this step requires knowledge of electrical ,mechanical, thermodynamic requirements and properties of the cell ,applkication and the meterials used in the pack
3.the third step is to design the protection of the cells particularly electrical protection the pack must be protected from indavereant maintaining internal and external to the pack as well as excessive charging and discharging imposed on its terminals
4.the fourth step is to design a control system that monitors and manages the cells keeping them from being damaged and maintaining the pack at peak performance
5.finally a pack performance best when it is used properly .the final section of this chapter describes how to charge and discharge the pack to make it perform its best
MECHANICAL CONNECTION
Design mechanical inter connects 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 interconnections for the expected maximum current carriying capability .improperly size tabed could heat up excessively resulting in even higer resistivity .for reliable welded connections at the terminals A123 systems recommends either pure nickel tabs or nickel clad copper tabs in addition other alloy afford both weldability strength and low resistance
which are all desirable features of a good interconnection cell interconnects should be neither soldered on the end caps
nor attached using extreme heat A123 systems period of time through a salient feature in the web tab these parameters
can be specified and regulated for a consistant high quality weld every time .
THE GAP BETWEEN EACH CELL
The cell vents located on the cap of the cell should not be blocked by any mechanical means blocking the cell vents and then sufficiently abusing the cell so to build u pressure in the cell prevents the cell from properly venting an ess designed to install cells to end needs end to end needs 1mm of space between the cells to allow the vent to open under fault condition
BATTERY DIMENSIONS
SERIES STRINGS
Cell combined in series strings can achive higer operating voltage by connecting the postive terminal of one cell to the negative terminal of the next battery .connect strings cells usung their current collection tabs in a manner
PARELLEL STRINGS
Cell combined in parellel strigs can achieve higer operating capacities by connecting like polaity terminals of adjacent cells to each other connect strings to parellel cells using their current collection tabs in a manner to that illustrated in figure
WE ARE USING CYLINDRICALS CELLS
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.A cylindrical cell consists of sheet-like anodes, separators, and cathodes that are sandwiched, rolled up, and packed into a cylinder-shaped can. This type is one of the first mass-produced types of batteries and is still very popular. These cells are suited for automated manufacturing
Here we are using the lego connecters
NICKEL STRIPS
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.Nickel has become most widely used in batteries due to its resistance to high voltages and conduction properties which means that the battery does not heat up upon heavy current flow. It is inexpensive and easily available and it can be easily weldNickel sulphate, a key ingredient in the batteries that drive electric vehicles, is another product of nickel sulphide and laterite ore. More than two-thirds of global nickel production is used in stainless steel. The addition of nickel enables stainless steel to become a versatile alloy.
The mechanical battery pack overall from starting to end
OVERALL BATTERY PACK CONSTRUCTION
