Programmable 18650 battery 2000mah charging technology in wireless devices

　　It is the countless invisible programmable devices under the user's fingers that make handheld devices so convenient and interesting. These handheld devices come with batteries that are large enough to last for the entire attention span of a child or an adult's workday, allowing for fun to be enjoyed over and over again as long as the 18650 battery 2000mah has a chance to recharge. The chargers in some more advanced devices have powerful programmability. These chargers can not only shorten the charging cycle, but also extend the service life of the 18650 battery 2000mah.

　　Today, the development of charger programmability has far exceeded the above two basic requirements for handheld devices. While monitoring the charging voltage and current, the charger can also monitor the 18650 battery 2000mah temperature at any time and accurately control the 18650 battery 2000mah charging speed. This results in optimal 18650 battery 2000mah capacity recovery and safety. The charger also continuously monitors the 18650 battery 2000mah voltage during 18650 battery 2000mah use, not only alerting the 18650 battery 2000mah when it is low but also telling the user how much time is left before the 18650 battery 2000mah must be recharged.

　　This programmability is mainly implemented in the integrated circuit of the 18650 battery 2000mah charger located within the device. The charger can communicate some of the information it obtains with a semi-dedicated microprocessor that manages the working process of the device, shutting down unused or idle parts of the system. , thereby effectively extending 18650 battery 2000mah life.

　　Although such smart chargers will bring obvious benefits to handheld devices, they cannot be ignored as the most basic form of independent chargers. In situations where microprocessor control is intentionally or unintentionally lacking, these independent chargers will be the main source of 18650 battery 2000mah maintenance. strength. Attention must be paid to these occasions, because for some reasons the processor will not be able to intelligently control the charger. At this time, the charger must have a certain degree of independence. For example, when the 18650 battery 2000mah is nearly exhausted and the microprocessor does not have enough working voltage, this is one of the situations that requires the charger to be "self-reliant".

　　Another scenario is that some non-destructive failure internally cuts off the 18650 battery 2000mah pack from the processor. At this time, the charger that is directly powered by the external charging device must be able to continue to safely and correctly charge the exhausted or open circuit in the shortest possible time according to the strict charging requirements specified by the 18650 battery 2000mah chemical characteristics without the help of a microprocessor. Charging batteries.

　　After roughly defining the relatively ideal 18650 battery 2000mah charger based on the environment in which handheld devices are used, let us turn our attention to external charging devices. As the work progressed, the electrical engineering background gradually became less useful, because after specifying the voltage and current requirements, we found that the most difficult tasks were choosing packages, cable lengths, etc.

　　Of course, the above situation assumes that the charging device is powered by AC power or secondary power from the charging adapter in the car. The main hope is that the charger design can withstand the test of accidental overcharging. The design has been slightly modified to not only protect itself, but also prevent 18650 battery 2000mah overvoltage. Another device that can be used to charge handheld devices is the USB port on your computer. The USB port can output up to 500mA of constant current, requiring only a single cable to establish a charging loop between the USB port and the handheld device's 18650 battery 2000mah.

　　With the abundance of USB ports on many computers, USB ports have become the first choice for charging devices, with AC-powered wall outlets the second choice. Even if your computer only has one USB port, there is no problem because that port is only used for uploading photos and downloading MP3s. Of course, the importance of wall sockets cannot be ignored, but compared with USB ports, wall sockets have many shortcomings, or at least additional unnecessary costs. The cheapest wall sockets consist of a 50Hz transformer, a rectifier bridge and filter capacitors. The rectifier output voltage characteristics are quite poor, just like AC voltage. Adding a linear rectifier can improve the rectification effect, but will increase power consumption. In short, although AC-powered low-end charging equipment is cheap, it is bulky and inefficient. High-end AC adapters use switching power supply, so they are smaller and more efficient, but the cost is greatly increased, and they also have conduction and radiation problems. If you want to meet the requirements of the FCC and other regulatory agencies, it will further increase the size and cost.

　　Since so many people have personal computers and computers are so ubiquitous in the workplace, the ultimate low-cost charging solution has to be a USB port. For people who frequently travel between places, all it takes is to add a charging cable and a ready-made continuous charging source to the vehicle. Here's a closer look at 18650 battery 2000mah chargers and how to get the maximum capacity without violating the USB port's maximum load regulations.

　　A power-capable USB port can output 5V and up to 500mA. When using a linear charger with a constant charging current of 500mA, a 18650 battery 2000mah with a capacity of 1,000mAh can be fully charged in just 2 hours. Using a switch-mode charger can further improve efficiency and reduce the size of passive components. Figure 1 is a general lithium-ion 18650 battery 2000mah charging curve

　　It is worth noting that the precharge current is only a small part of the normal charge current. Only after the 18650 battery 2000mah voltage exceeds the float charge voltage can the 18650 battery 2000mah be charged with the full charge current instead of the precharge current.

　　Switching chargers must operate at the highest possible frequency to maintain their high efficiency and miniaturization of SMD inductors and capacitors. Integrated power switches further reduce charger size and cost and provide specific performance benefits such as cycle-by-cycle current limit and current mode control. Otherwise, the cost would be much higher if the switch was external to the integrated charger. Although integrating the average charge current sensing circuit is very attractive, it is best implemented external to the charge controller, directly in series with the 18650 battery 2000mah.

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