18650 rechargeable battery lithium 3.7v 3500mah

　　18650 rechargeable battery lithium 3.7v 3500mah charger circuit principle

　　The charging chip we chose is TP4056. This chip has few peripheral components and the cost is not high. You can buy a bunch of them for a few dollars. You can clearly see from the schematic diagram that the required components are: one TP4056 and one 1.2K resistor. (The larger the resistance here, the smaller the charging current. The minimum is 1.2k. Since the chip supports a maximum charging current of 1A, it is the value of the 1.2K resistor), one 0.4Ω resistor, two 1K resistors, and two LED lights (red The light and green light are used to indicate the charging status of the battery. It is a green light when full and a red light when charging. Welding), male pin header, female pin header, solder and Dupont wire, etc.

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

　　With the materials in hand, our next job is to solder the circuit according to the schematic diagram. Since 4056 is smaller, we chose an adapter board. First we solder 4056 to the adapter board.

　　Note: Be careful not to connect the chip pins together! Required materials (the 1k current limiting resistor is not added in the above picture, but it should actually be included)

　　With the materials in hand, our next job is to solder the circuit according to the schematic diagram. Since 4056 is smaller, we chose an adapter board. First we solder 4056 to the adapter board.

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

　　Welded to perforated board

　　Okay, so far, the most important component and the most difficult component to solder has been successfully soldered. The next step is to solder these peripheral components to the perforated board. As for the things that need attention, they are mainly electrolytic capacitors and LEDs have positive and negative poles. When soldering, be careful not to solder them backwards, otherwise they will not work properly. Also, in the soldered parts, some components have very long pins, and there may be pins exposed behind the board. Depending on the situation, See below

　　Exposed pins

　　This phenomenon is also unavoidable during the welding process. Friends who are welding for the first time or are not skilled in hand should pay attention. Since the wire on the back is thin, be careful not to get it in the eyes. It is best to wear it when welding. 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 solder step by step according to the schematic diagram. Since there are few components, it will not take too much time. Here is a picture of successful welding.

　　renderings

　　Looking at the board from here, you can see that there are two pairs of pin headers. The upper pair is connected to the power supply. The upper pin is positive and the lower pin is negative. The input voltage is 5v. It can be powered by USB or other power supply, but the voltage is 5v, not too high, not too low. The lower pair of pins are connected to the rechargeable battery. The pin header is left to facilitate the insertion of the DuPont cable. The upper one is the battery negative, and the lower one is The power supply is positive. If the rechargeable battery voltage is 3.7v, it doesn't matter what size the battery is. Do not charge a 1.2v battery, because the voltage may burn the battery if it is higher than the normal charging voltage of 1.2v.

　　Give 18650 charging status

　　The above picture is a real picture of charging an 18650 lithium battery. It seems that we have successfully produced it. During normal charging, the red indicator light lights up, the charging current is about 1A, and the voltage is about 4.2v, which is enough to meet most battery charging needs. When the battery is full, the green light of the indicator light turns on and the red light goes out. At this time, the output current is close to 0.

　　Fully charged rendering (if there is no fully charged battery, remove the battery during testing)

　　After testing, our production was very successful. Friends, are you ready? What are you waiting for? Hurry up and make one. Be sure to pay attention to safety when making it!

　　This circuit has a charging status display function. The red light flashes and is charging, the green light flashes and is about to be fully charged. The green light illuminates and 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 in the lower right corner so that the battery output is 4.2V. Then adjust the adjustable resistor in the lower left corner so that the third pin of LM358 is 0.16V. That’s it. The charging current is 380mA, which is super fast. The three parallel-connected diodes are step-down to prevent the LM317 from overheating, and a heat sink must be added to the LM317. The triode 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 lithium battery cannot exceed 4.2V. If it exceeds 4.5V, permanent damage may occur. The discharge voltage of lithium batteries must not be lower than 2.2V, otherwise permanent damage may occur. This circuit uses the LM3420-8.4 dedicated lithium battery charge controller. When the battery pack voltage is lower than 8.4V, the LM3420 output pin ① (OUT) has no output current, and the transistor Q2 is cut off. Therefore, the voltage-adjustable voltage regulator LM317 outputs a constant current, and its current value depends on the value of RL.

　　Lithium-ion batteries have higher charging requirements. Overcharging will cause the battery to be scrapped. There is no risk of overcharging using the simplest charging circuit shown in Figure 1. This circuit limits the charging current to about 70mA via a 1μF capacitor. Connect the TL431 into a 4.2V voltage source in parallel with both ends of the battery. When the battery voltage is lower than 4.2V, TL431 cuts off. All current is charged into the battery. When the battery voltage rises to close to 4.2V, TL431 begins to play a shunt role. When the battery voltage is 4.2V, all current flows into 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 values of R2 and R3 must be accurate. You can test whether both ends of TL431 are 4.2V before connecting the battery. There is no transformer isolation between this circuit and 220V AC power, so you should connect the battery before plugging it into the socket to ensure personal safety.

　　Once the battery is exhausted and there is nowhere to charge it, you will be in a state of embarrassment. You can see many emergency chargers on the market that can charge mobile phones, including Sanyo's "Love Wife" series and cheap copycat No. 1 No. 5 chargers. An external stick that can be charged by the battery. However, the copycat charging stick with an AA battery has a small charging current and the battery is not durable. The battery will be over before it is fully charged. The high-frequency pulsation generated by the built-in pulse circuit may Damage to the electrical appliance itself. Sanyo's "Love Wife" needs to be powered by its own rechargeable battery, or like other power boxes on the market, it can be 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 shrink tube.

　　Soldering iron, tweezers, scissors.

　　Idea: As we all know, the standard voltage of AA nickel-metal hydride battery is 1.2V. The normal working voltage is generally 1.15V-----1.35V. After 4 cells are connected in series, the voltage range floats between 4.6V-----5.4V. This is just right. The standard voltage of composite USB (USB standard voltage is 5V, allowing positive and negative floating). The standard voltage of AA alkaline battery is 1.5V. The peak value at the factory is generally around 1.6V. The 4-cell voltage is 6V------6.4V (this exceeds If the USB voltage standard is exceeded, connecting it directly will burn out the USB device, so here we consider using a diode to reduce 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, which looks like a voltage. It is relatively high, but due to the internal resistance of both the circuit and the battery, the voltage during actual charging is often only a little over 5V, which is a safe voltage)

　　In order to make the appearance as beautiful as possible, I used an 8-cell AA battery box as the main material for this production. The battery box only uses the series connection of the four batteries, and the other side is used as space for the circuit part.

　　Circuit diagram: (Be sure to understand the definitions of the four USB pins and don’t connect them incorrectly!) When the switch is open, it is the step-down mode of the alkaline battery. When the switch is closed, it is the rechargeable battery mode (I use 4-cell Pinsheng 2500MAH nickel-metal hydride charger) Battery)

　　The production and welding process is as follows: the solder joints should be full and pulled off after welding to prevent false soldering. Add a heat shrink tube or insulating sleeve to the exposed part of the wire to prevent short circuit. After completion, use hot melt glue to fix the wire and parts to prevent slippage, breakage and short circuit.

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