The charging chip we chose is TP4056, which has fewer peripheral components and low cost. You can buy a pile for a few dollars. It can be clearly seen from the schematic diagram. The required components are: one TP4056 and one 1.2K resistor. (The larger the resistance, the smaller the charging current, the minimum is 1.2k, because the chip supports a maximum charging current of 1A, which is the value at 1.2K resistance), a 0.4Ω resistor, two 1K resistors, and two LED lights (red The light and the green light are used to indicate the battery charging status, the green light is full when it is full, and the red light when charging), two 10uf capacitors, considering the practicality, it should also have a hole board and an adapter board (because the 4056 chip is small, it is not convenient for manual labor

　　The charging chip we chose is TP4056, which has fewer peripheral components and low cost. You can buy a pile for a few dollars. It can be clearly seen from the schematic diagram. The required components are: one TP4056 and one 1.2K resistor. (The larger the resistance, the smaller the charging current, the minimum is 1.2k, because the chip supports a maximum charging current of 1A, which is the value at 1.2K resistance), a 0.4Ω resistor, two 1K resistors, and two LED lights (red The light and the green light are used to indicate the battery charging status, the green light is full when it is full, and the red light when charging), two 10uf capacitors, considering the practicality, it should also have a hole board and an adapter board (because the 4056 chip is small, it is not convenient for manual labor Welding), pin header male, pin header female, soldering tin and DuPont wire, etc.

　　Required materials (1k current-limiting resistor is not added in the above picture, it should actually have)

　　With the material, our next job is to solder the circuit according to the schematic diagram. Since the 4056 is small, we chose the adapter board. First, we soldered the 4056 to the adapter board.

　　Note: Be careful not to connect the chip pins together! Materials needed (1k current limiting resistor is not added in the above picture, it should actually have)

　　With the material, our next job is to solder the circuit according to the schematic diagram. Since the 4056 is small, we chose the adapter board. First, we soldered the 4056 to the adapter board.

　　Note: Be careful not to connect the chip pins together!

　　soldered to the hole board

　　Well, up to now, the most important components and the most difficult to solder components have been successfully soldered. The next step is to solder these peripheral components to the hole board. As for the places that need attention, the main ones are electrolytic capacitors and LEDs have positive and negative poles. Be careful not to reverse the soldering when soldering, otherwise it will not work properly. There is also a part where the soldering is good. Some components have very long pins, which may be exposed on the back of the board. See below

　　exposed pins

　　This phenomenon is also unavoidable in the welding process. Friends who are welding for the first time or those who are unskilled should pay attention to it. Because the wire behind the back is thin, be careful not to get your eyes. It is best to wear it when welding. For glasses, in order to avoid too many exposed pins, remember to cut off the pins in time after soldering some components to prevent accidents.

　　We are soldering step by step according to the schematic diagram. Since there are fewer components, it will not consume too much time. Here is a diagram of successful soldering.

　　renderings

　　From the billboard here, you can see that there are two pairs of pin headers, the upper pair is the power supply part, the upper pin is positive, the lower one is negative, the input voltage is 5v, you can use USB power supply, or you can choose other It is powered by the method, but the voltage is 5v, not too high or too low. The lower pair of pins is the part that connects to the rechargeable battery. The pin sockets are left to facilitate the insertion of the DuPont cable. The upper one is the battery negative, the lower one The power supply is positive. If the voltage of the rechargeable battery is 3.7v, it doesn't matter which size battery is. Do not charge the 1.2v battery. The battery may be burnt due to the normal charging voltage higher than 1.2v.

　　Charge the 18650

　　The picture above is a real shot of charging the 18650 lithium battery. It seems that we have made it successfully. During normal charging, the red indicator light is on, the charging current is about 1A, and the voltage is about 4.2v, which is enough to meet most of the battery charging needs. When the battery is fully charged, the green light will be on and the red light will be off. At this time, the output current is close to 0.

　　Full effect picture (if there is no fully charged battery, remove the battery during testing)

　　After testing, our production is very successful, friends, are you ready, what are you waiting for, do not hurry up to make one, you must pay attention to safety when making it!

　　This circuit has a charging status display function. The red light is flashing and it is charging, the green light is flashing and it is about to be fully charged, and the green light is on and it is fully charged. As long as you have a 12V power supply, don’t install the battery after connecting the circuit. Adjust the adjustable resistor on the lower right corner to make the battery output 4.2V, and then adjust the adjustable resistor on the lower left corner to make the third pin of LM358 0.16V. That's it, the charging current is 380mA, super fast, the three parallel diodes are step-down to prevent overheating of the LM317, and a heat sink must be added to the LM317. The transistor in the picture can be of any type

　　Lithium battery fast automatic charger circuit. Lithium batteries can be charged with high current, but the maximum charging voltage of a single-cell lithium battery cannot exceed 4.2V. If it exceeds 4.5V, it may cause permanent damage. The discharge voltage of the lithium battery must not be lower than 2.2V, otherwise it may cause permanent damage. This circuit uses the LM3420-8.4 dedicated lithium battery charging controller. When the battery pack voltage is lower than 8.4V, there is no output current at the LM3420 output pin (OUT), and the transistor Q2 is cut off. Therefore, the adjustable voltage regulator LM317 outputs a constant current, and its current value depends on the value of RL.

　　The charging requirements of lithium-ion batteries are higher. Overcharging will cause the battery to be scrapped. There is no risk of overcharging with the simplest charging circuit shown in Figure 1. This circuit limits the charging current to about 70mA through a 1μF capacitor. Connect the TL431 to a 4.2V voltage source in parallel at both ends of the battery. When the battery voltage is lower than 4.2V, TL431 is cut off. The current is fully charged into the battery. When the battery voltage rises to close to 4.2V, the TL431 begins to shunt. When the battery voltage is 4.2V, all current flows into the TL431. At this time, the power consumption of TL431 is 0.3W, which does not exceed the maximum power consumption. Because the charging current is small. Therefore, the long charging time is its shortcoming. In the circuit, the resistance of R2 and R3 must be accurate. Before connecting the battery, test whether the two ends of the TL431 are 4.2V. There is no transformer isolation between this circuit and 220V AC, so you should plug in the socket after connecting the battery to ensure personal safety.

　　Once the battery is exhausted and there is nowhere to charge, you will be embarrassed. There are many emergency chargers on the market that can charge mobile phones. There are Sanyo’s "Love Wife" series, and the cheap one is a No. 5 copy. An external stick that can be charged by the battery. However, a AAA battery charging stick in the cottage has a small charging current and the battery is not durable. It will be over before the battery is charged. The high-frequency pulsation generated by the built-in pulse circuit may be Damaged to the electrical appliance itself being charged. Sanyo "Love Wife" needs to be equipped with its own rechargeable battery, or like other power boxes on the market, it is powered by a built-in lithium battery.

　　8-cell battery box: 1.5 yuan, 3A fuse: 0.1 yuan, small switch: 0.5 yuan, 470UF capacitor: 0.2 yuan, USB2.0 socket: 0.5 yuan, diode: 0.1 yuan, a section of heat shrinkable tube.

　　Soldering iron, tweezers, scissors.

　　Idea: Everyone knows that the standard voltage of No. 5 Ni-MH battery is 1.2V. The normal working voltage is generally 1.15V-----1.35V. The voltage range after connecting 4 cells in series is between 4.6V and 5.4V. This is just right. The standard voltage of composite USB (USB standard voltage is 5V allows positive and negative floating) The standard voltage of AA alkaline battery is 1.5V. In accordance with the USB voltage standard, it will burn out the USB device when directly connected and used, so here is considered to use a diode to step down the voltage. The voltage drop of the crystal diode is less than 0.7V. After the voltage drop, the voltage is 5.3V to 5.7V. Higher, but due to the internal resistance of the circuit and the battery, the actual charging voltage is often only more than 5V, which is a safe voltage)

　　In order to make the appearance as beautiful as possible, I used an 8-cell No. 5 battery box as the main material for this production. The battery box only uses the 4 battery series part of it, and the other side is diverted to the space occupied by the circuit part.