What is a lithium battery module?
1. Definition of lithium battery module
The battery module can be understood as the intermediate product of the battery and the pack formed by the combination of lithium-ion cells in series and parallel, and the addition of a single battery monitoring and management device. Its structure must support, fix and protect the cells, which can be summarized into three major items: mechanical strength, electrical properties, thermal properties and fault handling capabilities. Whether it can fix the position of the cell in good condition and protect it from deformation that damages its performance, how to meet the current-carrying performance requirements, how to meet the control of the temperature of the cell, whether it can be powered off in the event of a serious abnormality, and whether it can avoid thermal runaway Communication, etc., will be the criteria for judging the pros and cons of battery modules. For high-performance battery modules, their thermal management solutions have turned to liquid cooling or phase change materials. As shown below:
2. Characteristics of lithium battery modules
1. The lithium battery module requires the battery to have a high degree of consistency (capacity, internal resistance, voltage, discharge curve, life).
2. The cycle life of a lithium battery module is lower than that of a single battery.
3. Use under limited conditions (including charging, discharging current, charging method, temperature, etc.).
4. After the lithium-lithium battery module is formed, the battery voltage and capacity have been greatly improved, and it must be protected by charging equalization, temperature, voltage and overcurrent monitoring.
5. The lithium battery module must meet the voltage and capacity requirements required by the design.
3. Lithium battery module unit
The battery module is an adjustable module with high flexibility of combination. Without a protective plate and a balance system, the remaining capacity of the 100% DOD cycle for more than 2800 cycles is ≥80%, which is safer, more environmentally friendly, more stable, and more stable. Efficient.
Capacity: Modular unit
Length: 400mm
Width: 150 mm
Height: 210 mm
Nominal voltage (V): can be adjusted according to demand
Weight of battery pack: ≤50 Kg
Standard charging current: 0.3C
Maximum continuous discharge current: 1C
Operating temperature range: -20～55℃
Cycle life (times): 80% DOD ≥ 4000 weeks
4. Composition of lithium battery module
1. Serial and parallel composition: The battery is composed of single cells connected in series. Parallel connection increases the capacity, the voltage remains unchanged, and the voltage doubles after the series connection, the capacity remains unchanged, such as a 3.6V/10Ah battery is composed of a single N18650/2Ah through 5 parallels. Parallel first and then series: Parallel connection will affect the battery cycle life after parallel connection due to differences in internal resistance and uneven heat dissipation. However, the failure of a single battery automatically exits, except for the capacity reduction, it does not affect the use after parallel connection, and the parallel connection process is stricter. When a unit battery in parallel is short-circuited, the parallel circuit current is very large, which is usually avoided by adding fuse protection technology. First in series and then in parallel: According to the capacity of the entire battery pack, first connect in series, such as 1/3 of the entire battery pack capacity, and finally connect in parallel, which reduces the failure probability of large-capacity battery packs.
2. Battery cell requirements: select the corresponding battery cells according to your own design requirements. The parallel and series batteries require the same type and model, and the difference in capacity, internal resistance and voltage value is not more than 2%. Under normal circumstances, after the batteries are combined in parallel and series, the capacity loss is 2%-5%. The more the number of batteries, the greater the capacity loss. Whether it is a flexible package battery or a cylindrical battery, multiple strings are required. If the consistency is poor, the battery capacity will be affected. The battery with the lowest capacity in a group determines the capacity of the entire battery group. High current discharge performance is required. The starting current of the motor is 3 times of the normal working current, and the high current discharge can improve the dynamic performance of the motor. The battery is required to have good heat dissipation. With a large number of batteries, the temperature rise of the batteries inside the battery box is not easy to dissipate, resulting in uneven temperature among the batteries, different discharge characteristics, and long-term battery performance degradation. The production technology level is high. The battery must be able to withstand the vibration shock of bumpy road surfaces. The production process, especially the spot welding process, has high requirements. After welding, test to prevent virtual welding and de-soldering.
3. The process of lithium battery module: Lithium battery module is realized in two ways, one is through laser welding or ultrasonic welding or pulse welding, which is a commonly used welding method. The advantage is that the reliability is good, but it is not easy to replace. The second is to contact through elastic metal sheets. The advantage is that no welding is required, and the battery is easy to replace. The disadvantage is that it may lead to poor contact.
5. Lithium titanate battery module
Lithium titanate battery products are based on the achievements of graphene technology. In terms of performance, they combine the high power density performance of supercapacitors and the high energy density characteristics of lithium batteries. They are more suitable for high power, high energy, wide temperature and other application conditions. Compared with iron phosphate Lithium battery with high rate (up to 10C), long life, wide operating temperature range, etc. The product can be widely used in power systems, new energy vehicles, rail transit and other fields.
2. Modular lithium battery pack
The lithium batteries produced by many lithium battery manufacturers have a fixed range value, which is set according to the needs; but the voltage required by the actual equipment is different. In order to provide the corresponding voltage or support capacity for the lithium battery, the It can only be achieved through the series and parallel connection of lithium batteries. This kind of demand for different needs is called modular demand, and the lithium battery made according to the modular demand is called a modular lithium battery pack, also called a customized lithium battery module.
