12V lithium battery protection board, 3 series lithium iron phosphate battery protection board, 18650 battery protection board, circuit board factory will give priority to the working principle of lithium battery protection board when designing double-sided circuit boards. The principle of the lithium battery protection board of the core, I hope it can play a role in inferring others. The circuit and parameters of the lithium battery protection board are different according to the use of IC, voltage, etc. The following is distributed with DW01 and MOS tube 8205A, including the normal working behavior of the lithium battery protection board.
The working principle of lithium battery protection board
When the cell voltage is between 2.5V and 4.2V, the first and third pins of DW01 both output high level (equal to the supply voltage), and the second pin voltage is 0V. At this time, the voltage of the 1st and 3rd pins of DW01 will be applied to the 5th and 4th pins of 8205A respectively. The two electronic switches in 8205A are in a conducting state because their G poles are connected to the voltage from DW01, that is, Both electronic switches are on. At this time, the negative pole of the cell is directly connected to the P- terminal of the protection board, and the protection board has a voltage output.
Protection board short circuit protection control principle
12V lithium battery protection board diagram In the process of external discharge of the protection board, the two electronic switches in 8205A are not completely equivalent to two mechanical switches, but are equivalent to two resistors with very small resistance, which are called 8205A The on-resistance of each switch is about 30m\U 03a9, and the total is about 60m\U 03a9. The voltage applied to the G pole actually directly controls the on-resistance of each switch. When the G-pole voltage is greater than 1V, the on-resistance of the switch is very small (tens of milliohms), which is equivalent to the switch being closed. When the G-pole voltage is less than 0.7V, the on-resistance of the switch is very large (a few tens of milliohms). MΩ), which is equivalent to the switch off. The voltage UA is the voltage generated by the on-resistance of the 8205A and the discharge current. When the load current increases, the UA will inevitably increase. Because UA0.006L&TImes;IUA is also known as the tube voltage drop of the 8205A, UA can be simply connected to indicate the size of the discharge current. . When it rises to 0.2V, it is considered that the load current has reached the limit value, so the output voltage of pin 1 is stopped, the voltage of pin 1 becomes 0V, the discharge control tube in 8205A is turned off, and the discharge circuit of the cell is cut off, which will turn off Discharge control tube. In other words, the maximum current that DW01 allows to output is 3.3A, which realizes overcurrent protection.
Protection board overcharge protection control principle
When the battery is normally charged by the charger, as the charging time increases, the voltage of the cell will become higher and higher. When the voltage of the cell rises to 4.4V, DW01 will consider that the voltage of the cell has been in the state of overcharge voltage. The output voltage of the 3rd pin is immediately disconnected, so that the 3rd pin voltage becomes 0V, and the switch tube in the 8205A is turned off because the 4th pin has no voltage. At this time, the B- of the battery cell and the P- of the protection board are in a disconnected state. That is, the charging circuit of the battery cell is cut off, and the battery cell will stop charging. The protective plate is overcharged and remains on. Wait until the P and P- of the protection board are indirectly connected to the discharge load. Therefore, although the overcharge control switch is turned off, the positive direction of the internal diode is the same as the direction of the discharge loop, so the discharge loop can be discharged. When it is placed below 4.3V, DW01 stops the overcharge protection state and outputs high voltage at pin 3 again, so that the overcharge control tube in 8205A is turned on, that is, the B- of the battery cell and the protection board P- are reconnected , the battery can be charged and discharged normally.
Protection board over-discharge protection control principle
When the cell is discharged through an external load, the voltage of the cell will gradually decrease, and the DW01 will monitor the cell voltage in real time through the R1 resistor. When the cell voltage drops to about 2.3V, DW01 will consider the cell voltage In the state of over-discharge voltage, the output voltage of pin 1 is immediately disconnected, so that the voltage of pin 1 becomes 0V, and the switch tube in 8205A is turned off because there is no voltage on pin 5. At this time, the B- of the battery cell and the P- of the protection board are in a disconnected state. That is, the discharge circuit of the cell is cut off, and the cell will stop discharging. The protection board is in an overdischarged state and remains there. After the P and P- of the protection board are connected to the charging voltage indirectly, DW01 stops the over-discharge state immediately after B- detects the charging voltage, and outputs a high voltage on the 1st pin again, so that the over-discharge control tube in the 8205A is turned on. That is, the B- of the cell and the P- of the protection board are reconnected, and the cell is directly charged by the charger.
Short circuit protection control process
The short-circuit protection of the 12V lithium battery protection board is an extreme form of over-current protection. Its control process and principle are the same as over-current protection. The short-circuit is only equivalent to adding a small resistance (about 0Ω) between P and P-. ) so that the load current of the protection board reaches more than 10A instantaneously, and the protection board immediately performs overcurrent protection.
Lithium battery charging circuit principle and application
Due to its excellent characteristics, lithium-ion batteries are widely used in portable electronic devices such as mobile phones, camcorders, notebook computers, cordless phones, power tools, remote control or electric toys, cameras, etc.
Lithium battery and NiCd, NiMH rechargeable battery:
The negative electrode of a lithium-ion battery is a graphite crystal, and the positive electrode is usually lithium dioxide. During charging, lithium ions move from the positive electrode to the negative electrode and are embedded in the graphite layer. During discharge, lithium ions are detached from the negative electrode surface in the graphite crystal and move to the positive electrode. Therefore, during the charging and discharging process of the battery, lithium always appears in the form of lithium ions, rather than in the form of metallic lithium. Therefore, this kind of battery is called a lithium-ion battery, or lithium battery for short.
Lithium batteries have the advantages of small size, large capacity, light weight, no pollution, high single-cell voltage, low self-discharge rate, and many battery cycles, but they are expensive. Nickel-cadmium batteries are being phased out due to their low capacity, serious self-discharge and environmental pollution. Nickel-metal hydride batteries have a high performance-price ratio and do not pollute the environment, but the single-cell voltage is only 1.2V, so the scope of use is limited.
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