Project 1 Mechanical design of battery pack

Battery pack capacity: 18 kWh

Cell: ANR26650M1-B

Prepare a detailed battery pack drawing along with its enclosure. State your assumptions.

Detailed introduction of 26650 lithium battery

There are two basic methods for naming lithium battery, one is from the positive material of lithium battery, the other is from the size. These two basic classifications start from the common aspects and have general characteristics. In addition, there is a classification from a certain performance or application, which starts from the aspect of personality and has specific characteristics. The 26650 lithium battery is classified in terms of size, so it has a common shape. Its cathode material, performance and application fields are diversified.

26650, which is strictly defined as the size of single electric core: diameter 26mm, height 65mm. The dimensions of this cylinder are slightly different from each manufacturer in the actual production. The so-called "tall, short, fat and thin" are different, all called 26650. But this difference will not be very big, the diameter will not exceed 27mm, and the height will not exceed 66mm. When a single cell is put into use with a support system, it is a 26650 lithium battery. If it is a combination of multiple lithium cells or lithium batteries, it is called a lithium battery pack. To be more precise, it is a 26650 lithium battery pack.

Like 18650 lithium battery, 26650 lithium battery can also use different positive materials. According to the current market application, there are 26650 ternary lithium battery and 26650 lithium iron phosphate battery. The difference between them is also the general difference between the ternary lithium battery and lithium iron phosphate battery. The former has the advantages of high capacity and voltage platform, while the latter has the advantages of safety and high starting current. Combined with the fact that 26650 lithium batteries are mostly used in equipment startup, 26650 lithium iron phosphate batteries are the main application, and the advantages of these batteries in safety and price are obvious.

Many factories will produce 26650 lithium iron phosphate batteries. Although they are personalized, their basic parameters should meet international standards. Below we choose to customize the relevant parameters of Dongguan Juda Electronics Co., Ltd., a lithium battery manufacturer, to give you a general understanding of 26650 lithium batteries. The company's 26650 lithium battery dimensions: 26.4 * 65.8mm maximum, 3000mAh nominal capacity, 3.2V nominal voltage, 3.65v and 2.5V charging and discharging cut-off voltage, 1500mah standard charging and discharging current, 1c charging and 1.5C discharging maximum, operating temperature of - 10 ℃ ~ + 60 ℃.

The 26650 lithium iron phosphate battery has stable charging and discharging performance, high temperature resistance, and cycle life three times that of ternary materials. Because it can charge and discharge with large current, it is very suitable for flashlight, miner's lamp, instrument and so on. Moreover, this advantage enables it to develop to large scale. For example, the 26650 power lithium iron phosphate battery technology of General Electronics Technology Co., Ltd has been mature.

The working principle of lithium-ion battery

Looking back on the development and application of lithium-ion batteries in the past 40 years, from wearable devices to electric vehicles, from communication base stations to space stations, all kinds of lithium-ion batteries of different sizes and weights are connected with our lives. The lithium-ion battery is an epoch-making invention, and its emergence quickly promotes the evolution of civilization and technology. And how is "electricity" obtained through the internal reaction of lithium-ion batteries?

The working principle of lithium-ion batteries can be explained in terms of charge state and discharge state. As its name, lithium-ion batteries use the transfer of "lithium" ions to complete the charge/discharge circuit.

In the charged state:

To achieve energy storage, Lithium ions will be released from the positive electrode that has lithium-containing. At this time, the lithium ions use the electrolyte as a transmission medium to diffusion and through the separator and then embed into the negative electrode material that can receive lithium ions.

In the discharge state:

The lithium ions will released from the negative electrode, and use the electrolyte as a transmission medium to diffusion and through the separator, and then return to the positive electrode.

Cathode:

A conductive aluminum foil is usually used as a current collector, and then a metal-oxide is containing "lithium" is coated with a solvent, a binder, a conductive agent, and add a little conductive material. The cycle life of lithium-ion batteries is closely related to the material used in the positive electrode. Studies have shown that if lithium iron phosphate is used as the main positive electrode material, the battery cycle life is estimated to reach 30,000 times; If you choose to use the ternary system (Ni-Mn-Co NMC/Ni-Mn-Al NCA), only a few thousand times. There are many development potentials and opportunities for the positive electrode process. For example, The introduction of additives that can improve battery safety into the positive electrode process. It is one of the focuses of the future development of the lithium-ion battery industry.

Anode:

As the advantages of stable cost and high safety, up to 90% of lithium-ion batteries on the market use graphite as the anode material. In the lithium-ion battery market (such as smartphones, Tesla, Gogoro, etc.) gradually pursuing the development trend of high capacity, many research teams have invested in the development of silicon-based anode materials based on silicon or silicon oxide in order to improve the energy density of the battery.

Separator:

The microporous film made of polypropylene (PP)/polyethylene (PE) and other plastics, placed between the positive and negative plates to block the positive and negative electrodes to avoid battery self-discharge and short-circuit between the two poles problem. The separator is full of dense micropores, in order to make lithium ions can through, allowing the battery to form a complete charge and discharge circuit.

Electrolyte:

As a medium for the transfer of lithium ions between the positive and negative electrodes, the common main components of lithium-ion battery electrolytes, including EC, DMC, and PC, etc., as an extremely important role in the performance of lithium-ion batteries. If you want to improve the battery cycle life, safety, and lithium-ion transmission characteristics, you can start to improve the electrolyte formulation and electrolyte additives. Proper lithium-ion battery electrolyte can maximize the performance of lithium-ion batteries.

Nanaophosphate High Power LithiumIon Cell ANR26650M1-B

A123’s high-performance Nanophosphate® lithium iron phosphate (LiFePO4) battery technology delivers high power and energy density combined with excellent safety performance and extensive life cycling in a lighter weight, more compact package. Our cells have a low capacity loss and impedance growth over time as well as high usable energy over a wide state of charge (SOC) range, allowing our systems to meet end-of-life power and energy requirements with minimal pack oversizing.

Applications of the battery.

There are various applications of Lithium-ion cells

1. COMMERCIAL SOLUTIONS This is a large-scale application for the battery where high power is required. Datacenter UPS Telecom backup IT backup Autonomously guided vehicles Industrial robotic and material handling equipment

2. GOVERNMENT SOLUTIONS Military vehicles military power grids

3. GRID SOLUTIONS Frequency regulation Renewable integration REverse capacity Transmission and distribution

4. TRANSPORTATION SOLUTIONS Plug-in hybrid vehicles, hybrid cars, electric vehicles Commercial vehicles Off-highway vehicles passenger vehicles.

The performance of the cell is given in the datasheet that is referred to for this project. These images show the power discharge, current discharge, and the life cycle of the cells used for the battery pack.