There are three main types of lithium battery BMS, one is titanium lithium BMS, one is lithium iron phosphate BMS, and the other is ternary lithium BMS. Titanium lithium is mainly aimed at large power vehicles, and it is becoming more and more important at present. Our company is one of the few companies that can produce titanium-lithium BMS. Today, we mainly talk about lithium iron phosphate BMS and ternary lithium BMS. I will introduce titanium and lithium in detail in a separate article.
The difference between lithium iron phosphate battery and ternary lithium battery BMS:
LiFePO4 battery BMS:
The lithium iron phosphate battery has a single voltage of 3.2V, and is now generally used as a power source for electric vehicles. Lithium iron phosphate batteries for electric vehicles are made of many single cells in series or parallel to achieve different voltage and capacity levels. Due to the discrete nature of lithium batteries, after a period of use, the voltage of each battery will become more and more different, some are higher than 3.2V, some are lower than 3.2V, which has a great impact on the entire lithium battery pack, and the overall capacity changes. small, the lifespan is shortened.
The lithium iron phosphate battery pack BMS is useful and necessary. The BMS circuit can detect the voltage and current of each battery in the series lithium battery pack separately, and control the charging and discharging process of the battery pack. The voltage of each battery in the lithium iron phosphate battery is between the overcharge detection voltage and the overdischarge detection voltage, and when there is no short circuit in the output, the MOS transistor is turned on, and P+ and P- output the battery pack voltage, allowing the lithium battery pack to perform operation. Charge and discharge work.
In addition, the lithium battery BMS also has the functions of battery pack over-discharge protection, over-charge protection, over-current protection, and short-circuit protection.
Ternary lithium battery BMS:
Ternary polymer lithium battery refers to a lithium battery whose positive electrode material uses a ternary positive electrode material of lithium nickel cobalt manganese or lithium nickel cobalt aluminate. There are many kinds of positive electrode materials for lithium ion batteries, mainly lithium cobalt oxide, lithium manganate, Lithium nickelate, ternary materials, lithium iron phosphate, etc. At present, the lithium battery of ternary material has replaced the lithium cobalt oxide battery that was widely used before, and is widely used in the field of notebook batteries.
Materials that are relatively balanced in terms of capacity and safety have better cycle performance than normal lithium cobalt oxide. In the early stage, due to technical reasons, the nominal voltage was only 3.5-3.6V, which limited the scope of use. With continuous improvement and perfect structure, the nominal voltage of ternary lithium battery has reached 3.7V, and its capacity has reached or exceeded the level of lithium cobalt oxide battery.
Due to the high energy density of ternary lithium batteries, it is difficult to ensure the safety of the batteries. Specifically, in the overcharged state, the electrolyte will be decomposed, causing the temperature and pressure inside the lithium battery to rise; in the overdischarged state, the electrolytic material in the negative electrode - copper will melt and cause an internal short circuit, increasing the temperature: Due to the characteristics of high internal resistance, the internal power consumption of the battery increases, and the temperature also rises, which may cause oxidation or decomposition of the electrolyte, resulting in a shortened life of the lithium battery.
Since the ternary lithium battery has the shortcomings analyzed above, a protection circuit must be added in the application of the lithium battery.
The ternary lithium battery protection circuit needs to have the following functions:
(1) If the charging voltage exceeds the allowable value of the battery, a battery discharge circuit can be provided.
(2) If the discharge voltage is lower than the minimum allowable value of the battery, a battery charging circuit can be provided. The battery is then disconnected from the external circuit, and the battery is then disconnected from the external circuit.
(3) If the charging and discharging current of the lithium battery is greater than the limit value, the connection between the battery and the external circuit is cut off.
(4) When the ternary lithium battery returns to the normal state, the protection circuit should be able to release the protection state accordingly, so that the battery can continue to work normally.
As the source of power for electric vehicles, batteries are naturally one of the most important components. All uses of electric vehicles, such as battery life, charging and discharging, are inextricably linked with the performance of the battery. At present, domestic power batteries are mainly divided into two factions, which are divided into lithium iron phosphate and ternary materials according to the difference of cathode materials. In the battery industry in recent years, the ternary lithium battery has attracted attention from all walks of life while becoming a dark horse in the industry. The market competition for ternary lithium batteries is still a hundred flowers. With the ever-changing and continuous innovation of battery technology, revolutionary changes are expected in the near future. The ternary lithium battery, which has matured in technology, has a place in the market by virtue of its own advantages.
Lithium iron phosphate batteries and ternary lithium batteries are widely used because of their large discharge current, low internal resistance, long life, and no memory effect. Lithium-ion batteries are strictly prohibited from overcharging, over discharging, and short circuit during use, otherwise the battery will be damaged. Fire, explosion and other fatal shortcomings, so when using rechargeable lithium batteries, there will be a protective plate to protect the safety of the cells. The function of the BMS is mainly to protect the cells of the rechargeable battery, maintain the safety and stability of the battery during charging and discharging, and play an important role in the performance of the entire battery circuit system.
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