1、 What is a lithium battery module?
1. Definition of lithium battery modules
A battery module can be understood as an intermediate product between lithium-ion cells and packs formed by combining them in series and parallel, and installing a single battery monitoring and management device. Its structure must provide support, fixation, and protection for the battery cell, which can be summarized into three major items: mechanical strength, electrical performance, thermal performance, and fault handling ability. Whether the position of the battery cell can be properly fixed and protected from damaging deformation, how to meet the current carrying performance requirements, how to control the temperature of the battery cell, whether to cut off power in case of serious abnormalities, whether to avoid the spread of thermal runaway, and so on, will all be the criteria for evaluating the quality of battery modules. The thermal management solutions for high-performance battery modules have shifted towards liquid cooling or phase change materials.
2. The characteristics of lithium battery modules
(1) Lithium battery modules require batteries to have a high degree of consistency (capacity, internal resistance, voltage, discharge curve, lifespan).
(2) The cycle life of lithium battery modules is lower than that of individual batteries.
(3) Use under limited conditions (including charging and discharging currents, charging method, temperature, etc.).
(4) After the formation of lithium-ion battery modules, the battery voltage and capacity have greatly increased, and it is necessary to protect them by conducting charging balancing, 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 combination flexibility. In the absence of a protection board and balancing system, the remaining capacity of the 100% DOD cycle for more than 2800 cycles is ≥ 80%, making it safer, more environmentally friendly, more stable, and more efficient to use.
Capacity: Module Unit
Length: 400 mm
Width: 150 mm
Height: 210 mm
Nominal voltage (V): can be adjusted according to demand
Battery pack weight: ≤ 50 Kg
Standard charging current: 0.3C
Maximum continuous discharge current: 1C
Working temperature range: -20~55 ℃
Cycle life (times): 80% DOD ≥ 4000 weeks
4. Composition of lithium battery modules
(1) Series parallel composition: The battery is composed of individual batteries connected in parallel. Parallel connection increases capacity while keeping the voltage constant. After series connection, the voltage doubles while keeping the capacity constant. For example, a 3.6V/10Ah battery is composed of a single N18650/2Ah battery passing through 5 parallel connections. Parallel connection before series connection: Due to differences in internal resistance and uneven heat dissipation, the battery cycle life after parallel connection can be affected. But if a single battery fails, it will automatically exit, except for a decrease in capacity, which does not affect the use after parallel connection. The parallel connection process is more strict. When a unit battery in parallel is short circuited, causing a very high current in the parallel circuit, it is usually avoided by adding fuse protection technology. Series first and then parallel: Based on the capacity of the entire battery group, series connection is carried out first, such as 1/3 of the capacity of the entire group, and finally parallel connection is carried out to reduce the probability of failure of large capacity battery groups.
(2) Cell requirements: Select corresponding cells according to your own design requirements. The types and models of batteries in parallel and series should be consistent, and the differences in capacity, internal resistance, and voltage values should not exceed 2%. In general, when batteries are combined in parallel and series, the capacity loss is 2% -5%. The more batteries there are, the more capacity loss there is. Both flexible packaging batteries and cylindrical batteries require multiple series combinations. If the consistency is poor, it will affect the battery capacity. The battery with the lowest capacity in a group will determine the capacity of the entire battery group. Require high current discharge performance. The starting current of the motor is three times the normal working current, and high current discharge is necessary to improve the motor's power performance. Require good battery heat dissipation. There are a large number of batteries, and the temperature rise of the batteries inside the battery box is not easy to dissipate, resulting in uneven temperature between the batteries and inconsistent discharge characteristics, which can lead to a long-term decline in battery performance. High level of production technology. The battery should be able to withstand the vibration and impact of bumpy road surfaces. High requirements are placed on production processes, especially spot welding processes. After welding, conduct a test to prevent false soldering and detachment.
(3) The process of lithium battery modules: Lithium battery modules can be achieved through two methods: laser welding, ultrasonic welding, or pulse welding. This is a commonly used welding method, which has the advantage of good reliability but is not easy to replace. The second is through contact with elastic metal sheets, which has the advantage of no welding and easy battery replacement, but the disadvantage is that it may lead to poor contact.
5. Lithium titanate battery module
Lithium titanate battery products are based on graphene technology achievements, combining the high power density performance of supercapacitors with the high energy density characteristics of lithium batteries in terms of performance. They are more suitable for high-power, high-energy, wide temperature and other application conditions. Compared with lithium iron phosphate batteries, they have characteristics such as high rate (up to 10C), long lifespan, and wide working temperature range. This product can be widely used in fields such as power systems, new energy vehicles, and rail transit.
2、 Modular lithium battery pack
Many lithium battery manufacturers produce lithium batteries with a fixed range value, which is set according to demand; However, the actual voltage required by devices is different. In order to provide the corresponding voltage or support capacity for lithium batteries, it can only be achieved through series and parallel connection of lithium batteries. This type of demand is called modular demand, and the lithium batteries made according to modular demand are called modular lithium battery packs, also known as customized lithium battery modules.