Advantages of lithium battery related structures and Protection Circuit Analysis Scheme Reprinted from: http://news.cecb2b.com/info/20120314/33451.html Lithium ionBatteryWith its excellent features, it is widely used in:
Mobile phones, video recorders, laptops, cordless phones, power tools, remote control, electric toys, cameras, and other portable electronic devices. 1. Lithium Battery It can be charged with nickel-cadmium or nickel-mh Battery : Lithium ion Battery The anode is graphite crystal, and the cathode is usually lithium oxide. When charging, the lithium ion is embedded into the graphite layer by moving toward the anode. When discharging, the lithium ion moves from the inner anode surface of graphite crystal to the cathode. Therefore Battery In the process of charging and discharging, lithium always appears in the form of lithium ion, rather than in the form of lithium metal. Therefore Battery It is called a lithium-ion battery. Lithium Battery has the advantages of small size, large capacity, light weight, no pollution, high single-node voltage, low self-discharge rate, and many battery cycles, but the price is relatively high. Due to its low capacity, serious self-discharge, and environmental pollution, nickel-cadmium batteries are gradually being eliminated. Ni-MH battery has a high performance price and does not pollute the environment, but the single voltage is only 1.2 V, so the use range is limited. Ii. Lithium Battery features: 1. higher weight-energy ratio and volume-Energy Ratio; 2. the voltage is high. The voltage of a single lithium battery is 3.6 V, which is equal to the series voltage of three nickel-cadmium or nickel-Mh rechargeable batteries; 3. self-discharge small storage for a long time, which is the most prominent advantage of the battery; 4. No memory effect. Lithium Battery does not have the so-called memory effect of nickel-cadmium battery, so the lithium battery does not need to discharge before charging; 5. long service life. Under normal operating conditions, the battery/discharge cycles are much higher than 500; 6. fast charging. Lithium Battery can usually use 0.5 ~ Twice the capacity of the current charging, so that the charging time is shortened to 1 ~ 2 hours; 7. It can be used in parallel at will; 8. Because the battery does not contain cadmium, lead, mercury and other heavy metal elements, it has no pollution to the environment and is the most advanced Green battery; 9. high cost. Compared with other rechargeable batteries, lithium batteries are more expensive. Iii. Internal Structure of Lithium Battery: Lithium Battery has two types of shapes: cylindrical and rectangular. The internal structure of the battery is spiral wound, and the separation material of polyethylene film with very fine permeability is separated between the positive and negative ends. The positive electrode consists of lithium and cobalt oxide lithium ion collection pole and the current collection pole composed of Aluminum film. The anode is composed of the lithium ion collector and the current collector composed of copper films. The battery is filled with an organic electrolyte solution. A safety valve and PTC Element are also installed to protect the battery from damage when the battery is abnormal and the output is short-circuited. The voltage of a single lithium battery is 3.6 V, and the capacity cannot be infinitely large. Therefore, a single lithium battery is often treated in series and in parallel to meet the requirements of different occasions. Iv. lithium battery charging and discharging requirements; 1. Lithium Battery Charging: according to the structure characteristics of the lithium battery, the maximum charge termination voltage should be 4.2 V and cannot be overcharged. Otherwise, the battery will be decommissioned because the lithium ion of the positive electrode is taken too much. Its charge and discharge requirements are high, you can use a dedicated Constant Current, Constant Pressure charger for charging. Usually the constant current charging to 4.2 V/after the transfer to the constant voltage charging, when the constant voltage charging current to 100mA or less, should stop charging. Charging current (MA) = 0.1 ~ 1.5 times the battery capacity (such as 135 mah battery, the charging current can be controlled in ~ Between 2025mA ). The conventional charging current can be about 0.5 times the battery capacity, and the charging time is about 2 ~ 3 hours. 000000000000 2. lithium battery discharge: due to the internal structure of the lithium battery, the lithium ion cannot be moved to the positive pole during discharge, and a part of the lithium ion must be retained in the negative pole, to ensure that the lithium ion can be smoothly embedded into the channel during next charging. Otherwise, the battery life is shortened accordingly. In order to ensure that some lithium ions are left in the graphite layer after discharge, the minimum discharge voltage must be strictly limited, that is, the lithium battery cannot be discharged too much. The discharge termination voltage is usually 3.0 V/section, and the minimum is not less than 2.5 V/section. The duration of battery discharge is related to the battery capacity and discharge current. Battery discharge time (hours) = battery capacity/discharge current. The discharge current (MA) of lithium battery should not exceed 3 times of the battery capacity. (For example, mah battery, the discharge current should be strictly controlled within 3A) otherwise the battery will be damaged. Currently, all lithium batteries sold on the market are enclosed with protective boards for charge and discharge. You only need to control the external charge and discharge current. V. Protection Circuit of Lithium Battery: The charging and discharging protection circuit of Two lithium batteries is shown in. Composed of two FET tubes and dedicated protection Integrated Block S--8232, over-Charge Control Tube fet2 and over discharge control tube fet1 are connected in circuit, by protection IC Monitoring The battery voltage is controlled. When the battery voltage rises to 4.2v, the overcharging protection tube fet1 ends and the charging stops. To prevent misoperation, a delay is usually added to the external circuit. Capacitor . When the battery is in the discharge state and the battery voltage drops to 2.55v, the discharge control tube fet1 ends and the power supply to the load is stopped. When there is a large current flow on the load, the overcurrent protection controls fet1 to stop discharging to the load, in order to protect the battery and Fet. Overcurrent detection is based on the conduction of the Fet. Resistance As Detection Resistance , Monitoring The voltage drop stops when the voltage drop exceeds the set value. There is also a delay circuit in the circuit to distinguish the Surge Current and short-circuit current. This circuit has complete functions and reliable performance, but it is highly professional and not easy to purchase. It is not easy for amateurs to copy it.
Vi. Simple charging circuit: Many sellers now sell single-cell lithium batteries without charging boards. Its superior performance and low price can be used for maintenance replacement of self-made products and lithium batteries, so it is favored by the majority of Electronic enthusiasts. Interested readers can refer to figure 2 to create a charging board. The principle is: Use a constant voltage to charge the battery, to ensure that it will not overcharge. The input DC voltage is 3 V higher than the charged battery voltage. R1, Q1, W1, Tl431 It is a precision Adjustable Voltage regulator circuit. Q2, W2, and R2 constitute an Adjustable Constant Current Circuit. Q3, R3, R4, R5, LED For the charging indicator circuit. As the voltage of the rechargeable battery increases, the charging current will gradually decrease. When the battery is full, the pressure drop on R4 will decrease, thus ending Q3,
LED Turn off. To ensure sufficient battery, continue charging after the indicator is off for 1-2 hours. During use, install appropriate rules for Q2 and Q3. Radiator . The advantages of this circuit are: simple production, Components Easy to buy, safe charging, intuitive display, and will not damage the battery. You can change W1 to charge multiple series lithium batteries, and change W2 to adjust the charging current in a wide range. Disadvantage: No overdischarge control circuit. Figure 3 shows the Printed Board of the charging Board (from the perspective of the component ).
VII. Example of single-cell lithium battery application 1. Used as a replacement product for battery pack Maintenance There are many battery packs, such as those used in laptops. After maintenance, it is found that the battery pack is damaged only when the battery is faulty. You can choose a suitable single lithium battery for replacement. 2. Create a highlighted micro-clip I have used a single 3.6v1.6ah lithium battery with a super-high-brightness white light emitting TUBE TO MAKE A micro fuse, easy to use, small and beautiful. In addition, because of the large battery capacity, the average usage per night is half an hour, and no charge is required for more than two months. Circuit 4.
3. replace 3 V Power Supply The voltage of a single lithium battery is 3.6 V. Therefore, only one lithium battery can replace two ordinary batteries to power the radio, Walkman, camera and other small household electrical appliances, which is light weight and has been used for a long time. 8. Storage of lithium batteries: The lithium battery should be retained after sufficient power supply. It can be stored at 20 ℃ for more than half a year. It can be seen that the lithium battery is suitable for low temperature storage. Someone suggested storing rechargeable batteries in a refrigerator to store them. IX. Usage notes: The lithium battery cannot be disassembled, drilled, punctually inserted, sawed, pressurized, or heated. Otherwise, serious consequences may occur. Lithium batteries without charging protection boards cannot be short-circuited and cannot be used for children to play. It cannot be close to flammable articles or chemicals. The decommissioned lithium battery should be properly handled.
