Types and Differences of Power Batteries

Ⅰ. Main types of power batteries

At present, the mainstream technologies in the market are still dominated by lead-acid battery technology, nickel metal hydride battery technology, fuel cell technology, and lithium battery technology.

1. Ni-MH battery

Nickel-metal hydride (Ni/MH) batteries have good resistance to overcharge and overdischarge, and there is no problem of heavy metal pollution, and there will be no increase or decrease of electrolyte during the working process. It can achieve a sealed design and maintenance-free.

Compared with lead-acid batteries and nickel-cadmium batteries, nickel-metal hydride batteries have higher specific energy, specific power and cycle life. The disadvantage is that the battery has a poor memory effect. Moreover, as the charge-discharge cycle proceeds, the hydrogen storage alloy gradually loses its catalytic ability, and the internal pressure of the battery will gradually increase, which will affect the use of the battery. In addition, the expensive price of nickel metal also leads to higher costs.

In terms of key materials, nickel-metal hydride batteries are mainly composed of positive electrodes, negative electrodes, separators and electrolytes. The positive electrode is a nickel electrode (Ni(OH)2); the negative electrode generally uses metal hydride (MH); the electrolyte is mainly liquid, and the main component is potassium hydroxide (KOH). At present, the research focus of nickel-metal hydride batteries is mainly on the positive and negative electrode materials, and its technology research and development is relatively mature.

The Ni-MH battery for vehicles has been mass-produced and used, and it is the most widely used vehicle battery type in the development of hybrid electric vehicles. The most typical representative is the Toyota Prius, which is currently the largest mass-produced hybrid vehicle. PEVE, a joint venture between Toyota and Panasonic, is currently the world's largest manufacturer of nickel-metal hydride power batteries.

2. Fuel cells

A fuel cell is a power generating device that directly converts the chemical energy present in fuel and oxidant into electrical energy. Fuel and air are fed separately to the fuel cell, and electricity is produced. It looks like a battery with positive and negative electrodes and electrolytes from the outside, but in essence it cannot "storage electricity" but a "power plant".

Fuel cells are mainly composed of three parts: electrodes, electrolytes and external circuits. The fuel is mainly hydrocarbons such as hydrogen and methanol. Commonly used fuel cells can be divided into proton exchange membrane fuel cells (PEMFC), solid oxide fuel cells (SOFC), molten carbonate fuel cells (MCFC), phosphoric acid fuel cells (PAFC) and alkaline fuel cells according to their different electrolytes. battery (AFC). Among them, the proton exchange membrane fuel cell (PEMFC) has a variety of performance advantages, including low battery operating temperature and fast start-up speed. It is currently a relatively mature and widely used fuel cell, and it occupies a dominant position in global shipments.

In contrast to conventional chemical batteries, fuel cells can be supplemented with fuel, usually hydrogen. Some fuel cells can use methane and gasoline as fuel, but they are usually limited to industrial applications such as power plants and forklifts. The basic principle of a hydrogen fuel cell is that the reverse reaction of electrolyzing water supplies hydrogen and oxygen to the anode and cathode, respectively. After hydrogen diffuses outward through the anode and reacts with the electrolyte, electrons are released to reach the cathode through an external load.

The working principle of the hydrogen fuel cell is: it sends hydrogen to the anode plate (negative electrode) of the fuel cell, and through the action of the catalyst (platinum), an electron in the hydrogen atom is separated. Hydrogen ions (protons) that have lost electrons pass through the proton exchange membrane and reach the cathode plate (positive electrode) of the fuel cell, while electrons cannot pass through the proton exchange membrane. This electron can only reach the cathode plate of the fuel cell through the external circuit, thereby generating current in the external circuit.

After the electrons reach the cathode plate, they recombine with oxygen atoms and hydrogen ions to form water. Since the oxygen supplied to the cathode plate can be obtained from the air. Therefore, as long as hydrogen is continuously supplied to the anode plate, air is supplied to the cathode plate, and the water vapor is taken away in time, electric energy can be continuously provided.

The electricity generated by the fuel cell supplies power to the motor through inverters, controllers and other devices, and then drives the wheels to rotate through the transmission system and drive axle, so that the vehicle can run on the road. Compared with traditional vehicles, the energy conversion efficiency of fuel cell vehicles is as high as 60-80%, which is 2-3 times that of internal combustion engines.

The fuel of the fuel cell is hydrogen and oxygen, and the product is clean water. It works by itself without producing carbon monoxide and carbon dioxide, and without sulfur and particulate emissions. Therefore, hydrogen fuel cell vehicles are truly zero-emission and zero-pollution vehicles, and hydrogen fuel is the perfect vehicle energy source.

3. Lead-acid battery

Lead-acid battery has the longest application history, the most mature technology, and is the battery with the lowest cost and price. It has achieved mass production. Among them, the valve-regulated sealed lead-acid battery (VRLA) once became an important vehicle power battery, and was applied to EVs and HEVs developed by many European and American automobile companies. For example, the Saturn and EVI electric vehicles developed by GM lead-acid batteries in the 1980s and 1990s respectively.

However, the specific energy of lead-acid batteries is low, the battery lifespan is short, the self-discharge rate is high, the cycle life is low, the weight of the main raw material lead is large, and the environmental pollution of heavy metals may be generated during the production and recycling process. Therefore, at present, lead-acid batteries are mainly used for ignition devices when starting cars, and small equipment such as electric bicycles.

Ⅱ. Power battery VS ordinary battery

The main differences between power battery and ordinary batteries are as follows.

1. Different in nature

Power batteries refer to batteries that provide power for transportation vehicles, generally relative to small batteries that provide energy for portable electronic devices. The ordinary battery is a primary battery that uses lithium metal or lithium alloy as the negative electrode material and uses a non-aqueous electrolyte solution. It is not the same as rechargeable lithium-ion batteries and lithium-ion polymer batteries.

2. Different battery capacity 

In the case of all new batteries, we use a discharge meter to test the battery capacity. The capacity of general power batteries is around 1000-1500mAh, while the capacity of ordinary batteries is above 2000mAh, and some can even reach 3400mAh.

3. Different discharge power

A 4200mAh power battery can discharge its power in just a few minutes, but ordinary batteries cannot do it at all, so the discharge capacity of ordinary batteries cannot be compared with that of power batteries. The biggest difference between them is that it has a large discharge power and a high specific energy. Since the power battery is mainly used for vehicle energy supply, it has a higher discharge power than ordinary batteries.

4. Different applications

The batteries that provide driving power for electric vehicles are called power batteries, including traditional lead-acid batteries, nickel-metal hydride batteries and emerging lithium-ion power lithium batteries. It is divided into power type power battery (hybrid electric vehicle) and energy type power battery (pure electric vehicle). Lithium batteries used in consumer electronics such as mobile phones and laptops are generally referred to as lithium batteries to distinguish them from power batteries used in electric vehicles.

Ⅲ. Power battery VS energy storage battery

1. Power battery

It is specifically designed to provide the power required for electric vehicles. They need to have high energy density and power output to meet the acceleration performance and driving range requirements of electric vehicles. The design focus of the power battery is to improve the charging speed, discharging speed and cycle life of the battery. At the same time, safety is also an important aspect of power batteries to ensure reliable work under various conditions.

2. Energy storage battery

It is a battery system used to store electrical energy. They convert electrical energy into chemical energy, storing the charge in the battery and releasing it when needed. Energy storage batteries are usually designed for long-term energy storage and charging and discharging, such as playing an important role in grid dispatching, peak load shaving, and power management. The key features of energy storage batteries are high capacity, long cycle lifespan, and stable performance.

3. The differences between power battery and energy storage battery are as follows:

(1) Battery cycle lifespan

Power batteries and energy storage batteries have different requirements for service lifespan. Energy storage batteries typically need to have a longer cycle lifespan, being able to withstand thousands of charge and discharge cycles without significant degradation in performance.

Taking electric vehicles as an example, the theoretical life of the ternary lithium iron phosphate battery pack is 1,200 times. According to the frequency of use for three full charge and discharge once, the life of the ternary lithium battery reaches ten years. Energy storage batteries are more frequently charged and discharged than power batteries, and have higher requirements for cycle life under the premise of the same 10-year lifespan. If the energy storage power station and household energy storage are charged and discharged once a day, the cycle life requirement of the energy storage lithium battery can be greater than 3500 times; if the charge and discharge frequency is increased, the cycle life requirement is usually required to reach more than 5000 times.

(2) Application scenarios

Power batteries are used in new energy passenger vehicles, commercial vehicles, special vehicles, construction machinery and equipment, ships, etc. Power batteries pay more attention to power density and short-term high power output to meet the needs of electric vehicles for fast acceleration and long mileage. Compared with energy storage batteries, power batteries have higher requirements on energy density and power density. Furthermore, since the power battery is limited by the size and weight of the vehicle and the acceleration when starting, the power battery has higher performance requirements than the ordinary energy storage battery.

Energy storage batteries are widely used in grid energy storage, household energy storage, industrial and commercial energy storage, communication base stations and other fields. The design requirements of energy storage batteries are mainly optimized for energy density and long-term storage to meet the requirements for large capacity and long-lasting energy storage need. Since most energy storage devices of energy storage batteries do not need to be moved, energy storage lithium batteries do not have direct requirements for energy density; different energy storage scenarios have different requirements for power density; in terms of battery materials, pay attention to expansion rate and energy density , electrode material performance uniformity, etc., in order to pursue the long life and low cost of the entire energy storage device.

(3) Performance and design

The application scenarios of power batteries and energy storage batteries are different, so the performance and design of the two are also different. In order to ensure safety, the power battery as a mobile power supply naturally has high requirements for volume and energy density, and in this way can ensure sufficient and long-lasting battery lifespan, and if electric vehicles want to achieve safe and fast charging, the energy density and power of the power battery Density requirements should also be increased. Furthermore, since the power battery is limited by the size and weight of the vehicle and the acceleration when starting, the power battery has higher performance requirements than the ordinary energy storage battery.

(4) System structure and cost composition

The power battery PACK is basically composed of the following five systems: battery module, battery management system, thermal management system, electrical system and structural system. The cost of the power battery system consists of comprehensive costs such as batteries, structural parts, BMS, boxes, auxiliary materials, and manufacturing costs. The batteries account for about 80% of the cost. ) cost accounts for about 20% of the entire battery pack cost.

The energy storage battery system is mainly composed of battery pack, battery management system (BMS), energy management system (EMS), energy storage converter (PCS) and other electrical equipment. In the cost structure of the energy storage system, the battery is the most important component of the energy storage system, accounting for 60% of the cost; followed by the energy storage inverter, accounting for 20%, and the EMS (energy management system) accounting for 10%. BMS (battery management system) costs account for 5%, and others account for 5%.

(5) Battery management system (BMS)

BMS is the core of the battery pack. Whether the various functions and components of the battery pack can be coordinated depends on the battery management system BMS, and it can also directly affect the power output of the battery and the safety of the battery pack. The BMS of the battery management system of the power battery and the energy storage battery is different, because the power battery is mostly used in new energy vehicles, and it is often in high-speed motion. The power response speed and power characteristics of the battery, the SOC estimation accuracy, and the number of state parameter calculations are more rigorous. Requirements, and related adjustment functions also need to be realized through BMS.

Ⅳ. Common welding applications of power batteries

The interior of the power battery is also a whole complex system, from the battery cells, battery modules, battery packs, through a series of manufacturing processes, and finally assembled into a whole power battery system. This process involves a highly demanding welding process, that is, laser welding. In the production process of power batteries, laser welding has become the mainstream welding method, which has the advantages of flexibility, high efficiency and precision.

At present, in the production of power batteries, the link of using laser welding mainly includes middle process and post process.

Middle process: welding of tabs (including pre-welding), spot welding of poles, pre-welding of batteries into the shell, sealing welding of the top cover of the shell, sealing welding of the liquid injection port, etc.;

Post process: including the welding of the connecting piece when the battery PACK module is installed, and the welding of the explosion-proof valve on the cover plate behind the module, etc.

1. Battery adapter welding

The adapter piece and the flexible connection are the key components to connect the battery cover and the battery cell. It must take into account the battery's overcurrent, strength, and low-splash requirements at the same time. Therefore, it needs to have sufficient weld width during the welding process with the cover plate, and it needs to ensure that no particles fall on the battery cell to avoid short circuit of the battery. Copper, as the negative electrode material, is a highly reflective material with low absorption rate. It requires higher energy density to weld when welding.

2. Battery module and battery pack welding

The battery pack is composed of batteries to form a module, and then the modules are used to form a battery. The current technology has no modular battery pack. However, no matter which method is used, the cells are combined in series and parallel, and the basic components of the BMS battery management system will be added to it: such as the single battery monitoring and management device, and the cell protection structure, all of which require A soldering process is used to secure the cell.

3. Battery pole welding

The poles on the battery cover are divided into battery internal and external connections. The internal connection of the battery is the welding of the battery lug and the cover plate pole. The external connection of the battery is that the battery poles are welded through the connecting piece to form a series and parallel circuit to form a battery module.

The main problem of laser welding of battery poles is also the hole defect. The reason for it is similar to that of the explosion-proof valve. The pole weld is essentially the mating surface of the aluminum adapter block and the pole. The diameter of the hole in the aluminum block is only about 6 mm, where impurities such as stamping oil and cleaning agent are easy to remain. The high-energy-density laser causes the temperature of the weldment to increase sharply, resulting in the rapid vaporization of the remaining impurities at the pole, and the bubbles escape and overcome the surface tension of the molten pool to leave the molten pool, causing blasting defects. During this process, rapid changes in pulsed laser power further increase the tendency to form blast holes. Therefore, in addition to strengthening the pre-weld cleaning, the blast hole defects can also be reduced by optimizing the laser power variation.

4. Welding of battery positive and negative poles

The poles of the battery are the positive and negative contacts of the battery. Generally speaking, the positive electrode uses aluminum and the negative electrode uses copper. Its function is to weld the battery poles through the connecting piece to form a series and parallel circuit to form a battery module.

5. Welding of battery case and cover plate

The casing and cover plate of the power battery play the role of encapsulating the electrolyte and supporting the electrode material, providing a stable airtight environment for the storage and release of electric energy. Its welding quality directly determines the sealing and compressive strength of the battery, thus affecting the life and safety performance of the battery. The battery casing is mainly made of Al3003 aluminum alloy, its thickness is generally between 0.6 and 0.8 mm, and it is generally welded by low-power pulse laser.

6. Seal welding of battery explosion-proof valve

The explosion-proof valve is a thin-walled valve body on the battery sealing plate. When the internal pressure of the battery exceeds the specified value, the explosion-proof valve body is the first to rupture and deflate, releasing the pressure and preventing the battery from bursting. The structure of the explosion-proof valve is ingenious, and two aluminum metal sheets of a certain shape are firmly welded by laser welding. When the internal pressure of the battery rises to a certain value, the aluminum sheet breaks from the designed groove position to prevent the battery from further expanding and causing an explosion. Therefore, this process has extremely strict requirements on the laser welding process. It requires the weld seam to be sealed, strictly control the heat input, and ensure that the failure pressure value of the weld seam is stable within a certain range (generally 0.4~0.7MPa), too large or too small will have a great impact on the safety of the battery.

Ⅴ. What is the difference between voltage and power?

Voltage - the electric potential between one place and another. How much the electricity wants to move from one point to another. Measured in volts. Power - work that is being done per second.

Ⅵ. Does power mean voltage?

In electrical circuits, power is measured in volts (V), as well as in amperes (A). A volt is the unit of electric potential difference. Another way to explain volt is the force that sends electrons through an electrical circuit to establish an electric current that's measured in amperes.

Ⅶ. What are the 3 types of batteries?

There are three different types of batteries that are commonly used - Alkaline, Nickel Metal Hydride (NiMH), and Lithium Ion. The use of different metals and electrolytes in these batteries gives them different properties which means they are suited to different contexts.

Ⅷ. Is a battery a power source?

Batteries and similar devices accept, store, and release electricity on demand. Batteries use chemistry, in the form of chemical potential, to store energy, just like many other everyday energy sources.