Detailed explanation of BMS basic knowledge, application fields, and working principles
Composition of lithium battery
The lithium battery is mainly composed of two blocks, the battery cell and the protection board PCM (power battery is generally called the battery management system BMS). The battery cell is equivalent to the heart of the lithium battery, and the management system is equivalent to the brain of the lithium battery. The battery core is mainly composed of positive electrode material, negative electrode material, electrolyte, diaphragm and shell, while the protection board is mainly composed of protection chip (or management chip), MOS tube, resistor, capacitor and PCB board.
Lithium battery classification
Lithium batteries can be divided into two major categories: disposable non-rechargeable batteries and secondary rechargeable batteries (also known as storage batteries).
Non-rechargeable batteries such as lithium manganese dioxide batteries, lithium-thionamide batteries.
Secondary rechargeable batteries can be divided into the following classifications according to different situations.
1. According to the appearance: square lithium battery (such as ordinary mobile phone battery) and cylindrical lithium battery (such as 18650 for electric tools);
2. According to the outsourcing materials: aluminum shell lithium battery, steel shell lithium battery, soft pack battery;
3. According to the cathode material: lithium cobalt oxide (LiCoO2), lithium manganese oxide (LiMn2O4), ternary lithium (LiNixCoyMnzO2), lithium iron phosphate (LiFePO4);
4. According to electrolyte status: lithium ion battery (LIB) and polymer battery (PLB);
5. Divided by purpose: ordinary batteries and power batteries.
6. According to performance characteristics: high-capacity batteries, high-rate batteries, high-temperature batteries, low-temperature batteries, etc.
The key parameters of lithium batteries
The general lithium battery parameter range is: 50A 30V, 90A 30V, 110A 40V, 160A 60V.
Lithium battery application field
Batteries are mainly used in consumer products, digital products, power products, medical and security, etc.
Lithium battery protection board circuit diagram
Lithium is in the 3rd position on the periodic table of the elements, with one outer electron, which is easy to lose to form a stable structure, so it is a very active metal. Lithium-ion batteries are widely used because of their high discharge current, low internal resistance, long life, and no memory effect. Lithium-ion batteries are strictly prohibited from overcharging, over-discharging, and short-circuiting during use, otherwise it will cause the battery to catch fire or explode. Disadvantages, so when using rechargeable lithium batteries, there will be a protective board to protect the safety of the batteries.
Lithium battery protection board MOS tube
The protection board has two core components: a protection IC, which uses an accurate comparator to obtain reliable protection parameters; in addition, the MOSFET string acts as a high-speed switch in the main charge and discharge loop to perform protection actions. The circuit schematic diagram is as follows:
The following is an introduction: The lithium battery protection board is mainly composed of maintenance IC (overvoltage maintenance) and MOS tube (overcurrent maintenance). It is an equipment used to protect the safety of lithium battery cells. Lithium batteries are widely used by people with large discharge current, low internal resistance, long life, no memory effect, etc. Lithium-ion batteries are prohibited from overcharging, overdischarging, and short-circuiting, otherwise it will cause the battery to catch fire, blast and other death defects Therefore, when using rechargeable lithium batteries, there will be a maintenance board to maintain the safety of the batteries.
1. Voltage protection capability
Overcharge protection board: The protection board must have the ability to prevent the cell voltage from exceeding the preset value. Over-discharge maintenance: The protection board must have the ability to prevent the cell voltage from falling below the preset value.
2. Current capability
As a safety protection device for lithium batteries, the protection board must not only work reliably within the normal operating current scale of the equipment, but also be able to act quickly when the battery is accidentally short-circuited or over-current, so that the batteries are protected.
Definition: When the charging current is 500mA, the on-resistance of the MOS tube.
Due to the high operating frequency of communication equipment, the low bit error rate required for data transmission, and the steep rising and falling edges of the pulse train, the current output capability and voltage stability of the battery are required to be high, so the MOS switch of the protection board is turned on The time resistance should be small, and the single-cell battery protection board is usually 70mΩ. If it is too large, it will cause abnormal operation of the communication equipment, such as sudden disconnection of the mobile phone during a call, telephone connection failure, noise, etc.
4. Self-consumption current
Definition: The operating voltage of the IC is 3.6V. Under no-load conditions, the operating current flowing through the protection IC is generally very small.
The self-consumption current of the protection board directly affects the standby time of the battery. Usually, the self-consumption current of the protection board is less than 10 microamps.
5. Mechanical function, temperature adaptability, antistatic ability
The protection board must be able to pass the sensation and impact test of the national standard rules; the protection board can work safely at 40 to 85 degrees, and can withstand the ±15KV non-touch ESD electrostatic test.