As energy demand increases, the development of energy storage technologies has become a hot topic in the industry, accounting for 60% of energy storage system costs, and energy storage batteries have attracted widespread attention. Low-voltage lithium battery packs are becoming increasingly popular as an efficient and reliable energy storage solution.
1.What is a low voltage lithium battery for energy storage?
The low voltage lithium battery pack, as the name suggests, combines the three concepts of “low voltage”, “lithium battery” and “Pack”.
First, what is Pack?
A battery pack, also known as a battery module, is a type of packaging, encapsulation, and assembly process for battery production. It combines multiple individual cells in parallel and series to form a specific shape called a pack, according to customer requirements.
Secondly, what is a lithium battery?
In the current “photovoltaics + energy storage” household sector, lead-acid batteries and lithium-ion batteries are the mainstay of electrochemical energy storage technology, with lithium-ion batteries being the mainstay of electrochemical energy storage technology. The global installed capacity of electrochemical energy storage is expected to reach 21.1 GW in 2021. Of this, lithium-ion batteries accounted for 93.9%, lead-acid batteries for 2.2%, sodium-acid batteries for 2.0%, and liquid-current batteries for 1.2%. Compared with lead-acid batteries, lithium-ion batteries have excellent cycle times, energy density, response times, and are environmentally friendly. In the past, high costs have limited their development. In recent years, with technological advancements, costs have continued to decline, and lithium-ion batteries will become a major development direction in the future.
Finally, what is a low voltage battery?
Low-voltage batteries typically have a voltage in the 48-60V range, and when used, they cannot be connected in series to increase the voltage (i.e., regardless of the number of batteries, the voltage is always the same). Low-voltage batteries have low requirements for the BMS, are less affected by battery imbalance, and the technology is more mature, so the price is also relatively low.
The single voltage of the high voltage battery is generally 80-100V, the use of high voltage battery through series connection to strengthen, the final total voltage can be increased to about 400-600V (household storage), the high voltage storage battery in the BMS has higher technical and safety requirements, so the price is also higher.
Due to the high energy density of high-voltage battery cells, their safety characteristics are lower than those of low-voltage batteries, which are relatively more susceptible to spontaneous combustion or explosion. Low-voltage batteries can significantly reduce safety risks during transportation, installation, and use. In terms of the supply chain, the current limited supply of high-voltage batteries on the market makes it difficult for customers to purchase high-voltage batteries that meet their needs, while CHISAGE ESS low-voltage batteries offer a wider selection.
2.The composition structure of the low voltage lithium battery pack
A low voltage battery pack mainly consists of a single battery module, an electrical system, a box and several major BMS system parts.
Comparing a battery to the human body, the battery module can be considered the heart, responsible for storing and releasing electrical energy; the electrical system can be considered the arteries, blood vessels, and nervous system, which continuously deliver electrical energy from the battery to end devices and transmit real-time detection and control signals; the housing can be considered the skeleton, which plays a role in support, resisting mechanical impact, and protecting the environment; and the BMS can be considered the brain, responsible for measuring parameters such as voltage, current, temperature, and other parameters of the battery.
3. Principle and process of low-voltage lithium battery for energy storage
The basic operating principle of a low-voltage lithium battery pack is based on the electrochemical properties of redox reactions. During charging, lithium ions form LiCoO2 or LiFePO4 in the positive electrode material (e.g., LiCoO2 or LiFePO4), while simultaneously, in the negative electrode material (e.g., graphite), lithium ions migrate from the electrolyte to the metallic graphite and are reduced to lithium atoms. Upon discharge, the lithium ions return to the battery in reverse, forming LiFePO4 or LiCoO2, and are simultaneously oxidized to lithium ions.
Low-voltage lithium battery. The mainstream process of advanced laser welding and ultrasonic welding combines two methods. Laser welding uses a high-energy-density laser beam as a heat source, resulting in a highly efficient, precise welding method. Ultrasonic welding uses high-frequency vibration waves transmitted to the surfaces of two workpieces under pressure, causing friction on the surfaces of both workpieces and fusion between molecular layers. The CHISAGE ESS low-voltage battery pack uses laser welding technology, currently using the best German IPG laser, to avoid ultrasonic friction on the welding surface caused by pressure relief valve damage, and is more reliable.
4. Parameters and selection of low voltage lithium battery pack
The parameters of a low-voltage lithium battery pack and battery selection are closely linked to the need to consider installation, electrical, safety, and environmental issues. Below is an example of a low-voltage lithium battery pack CE48100-W (51.2V/100Ah) from CHISAGE ESS, illustrating the parameters to consider when selecting a battery:
Installation parameters
(1) Weight/dimensions
The CE48100-W weighs 55kg and measures 430×191.5x630mm. When choosing a battery pack, customers must consider the load-bearing capacity of the floor or wall and the available installation space, as well as whether the length, width, and height of the battery system will be limited within that space.
(2) Installation
CHISAGE ESS low-voltage lithium batteries are available in both floor-mount and wall-mount versions, allowing you to choose the right one based on your personal preference and the actual installation difficulty. The CE48100-W supports both installation types, and its simple and stylish design is suitable for a wide range of scenarios.
(3) Degree of protection
It indicates the ability of the electrical equipment enclosure to protect against the ingress of foreign bodies (dust, liquids, etc.), with the higher the level of protection, the better the effect. The CE48100-W has an IP65 rating, which is a higher level of protection.
Electrical parameters
(1) Nominal energy
Choosing the right battery capacity is a complex process. In addition to considering the load, you also need to consider the battery’s charging and discharging capacity, the maximum inverter power, the load’s operating hours, specific application scenarios, and so on. The CE48100-W has a rated capacity of 5.12 kWh, which basically meets the general battery storage needs of the entire family.
(2)Operating voltage
This voltage range must match the inverter’s battery input voltage range. A voltage higher than or lower than the inverter’s battery voltage range will result in the battery system not being able to be used with the inverter. The CE48100-W’s operating voltage range is 40~58.4V, which is suitable for any CHISAGE ESS home energy storage inverter.
(3) Maximum charge/discharge current
The maximum charge/discharge current supported by the battery system determines the battery charge/discharge time. The CE48100-W has a maximum charge current of 50A and a maximum discharge current of 100A, i.e., it supports 0.5C charging and 1C discharging.
Safety parameters
(1) Lithium-ion battery type
Lithium-ion batteries are mainly divided into lithium-cobalt batteries, lithium-manganese batteries, lithium-nickel batteries, lithium-iron phosphate batteries, lithium-ion batteries, and so on, depending on different cathode materials. Considering safety, stability, and cost-effectiveness, the CE48100-W uses a more stable and reliable lithium-iron phosphate battery.
(2) Warranty
Pay attention to the battery warranty terms, duration, and scope. Generally, two factors influence battery warranties: the warranty period and the number of cycles within a specified depth of discharge (DOD), with the first cycle reaching the warranty period. For example, the CE48100-W has a 5-year warranty (extended warranty of 10 years) and a cycle count of 6,000 at 80% DOD (depth of discharge). If 6,000 cycles are exceeded within the 5-year period, the warranty expires.
Environmental parameters
(1) Temperature range
Please pay attention to the ambient temperature range supported by the battery. Exceeding this temperature range will affect the normal use of the battery. The CE48100-W battery supports a charging temperature range of 0-55℃ and a discharging temperature range of -20-55℃.
(2) Humidity
For some humid or high altitude areas, please pay attention to this parameter, the humidity range of CE48100-W battery is 20~95%RH.
In addition, other features of low-voltage batteries should also be considered to provide users with a more convenient and comfortable user experience. For example, the CHISAGE ESS battery uses Class A batteries with larger usable capacity; it supports up to 15 batteries in parallel to meet the demand for battery capacity expansion; it also supports automatic BMS address setting, which is compatible with a wider range of inverters. Users can make the most suitable choice based on actual needs, taking into account the different functionalities of the batteries.
The low-voltage lithium battery energy storage system has broad application prospects in the new energy field. It is particularly well-suited for home energy storage systems and industrial/commercial energy storage systems, covering a wide range of applications in homes, offices, shopping malls, supermarkets, hospitals, and other multi-scenario applications. Its advantages, such as high safety, long life, and high energy density, make it an important trend in the development of energy storage technology. CHISAGE ESS will continue to devote itself to the research, development, and application of low-voltage lithium battery energy storage systems, contributing to the development of the new energy industry.
