Button batteryThe design saves a lot of costs. AA batteries are also designed to save costs and improve usability. They are also very common in the market. For example, one or 3 AA batteries can be easily purchased from department stores without the need for charging and maintenance, and can be replaced as needed. In fact, an AA battery also has a very simple drive circuit design, which is a A boost circuit with three components. The simplest is a 3-stage transistor. An inductor plus a few resistors and capacitors can work at a very low cost. A slightly better one is a control IC plus an inductor and a few resistors and capacitors. This kind of torch is also very common, but due to cost constraints of the drive circuit, the conversion efficiency is limited, and good LEDs are usually not used due to cost constraints, so the effect is limited.

More high-end, some designs can only use 4.2V single 10440 lithium batteries, and are also compatible with ordinary 1.5V 7 batteries and 4.2V 10440 lithium batteries, the same size as 7 batteries. This driver circuit is a boost and buck integrated Circuits are relatively expensive.

There are also batteries that can only use AA single cells or are compatible with 1.5v AA ordinary batteries or 4.2v single 14500 batteries, and their sizes are the same as AA batteries.

Further up, there are flashlights that use 4.2V single 18650 lithium batteries (commonly used in notebook batteries in the past). This is a popular street flashlight. It is more convenient to use. Some designs have charging on the main body of the welding torch. Socket, it can be charged by plugging in the charger. However, I remember that the 18650 slightly higher level torches did not have a charging port, so they needed to take out the battery to charge.

Again, this is a dual 18650 or more flashlight with a larger lithium battery size.

In addition, LED is also very important. Many cheap flashlights use domestic LEDs. There are problems with the luminous efficiency and light color of LED. Blue light has poor color rendering. It looks cold and white. Because people's eyes are very sensitive to blue and green light. , so it feels very bright. But when they light up the road at night, it is a white flower and the road cannot be seen clearly. Better LEDs are warm white or yellow, which don't look too bright, But the road condition is easier to see. As for the luminous efficiency, it can also be simply said that the same 1W power input to the LED can emit "how bright light". In terms of brightness or luminous flux, this will no longer expand. Generally speaking, it is the same The power, luminous efficiency is higher and brighter. Imported LEDs do a better job than most domestic LEDs - at least as far as I know, such as Cree, Osram, Philips, etc.

For lithium batteries, there are also issues with safety, chargers and charging maintenance.