With the development of modern society, entertainment methods have begun to shift to the outdoors, and many entertainment venues have also begun to tend to be outdoors. Portable Bluetooth players are one of the devices that produce entertainment outdoors. With its compact, portable, high-quality speaker effect, and integrated household electric player and special Bluetooth transmission function, it has become the first choice for outdoor entertainment equipment in modern society. Due to portability requirements, providing a safe, efficient, stable, portable, and sufficient backup power solution for portable Bluetooth players has become an important guarantee for people's long-term outdoor entertainment. With its unique advantages, backup batteries for portable Bluetooth players have become the first choice for power solutions for outdoor entertainment equipment.

1. Design requirements for portable Bluetooth players with lithium battery backup.

The working current of the player is relatively small, but to realize the continuous working time of the device, at least 8 hours of battery working time is required. The battery should have the function of overheating protection, the finished battery shall meet the requirements of UL2054 certification, and the weight of the battery must be controlled within 200g. To this end, our company uses imported Samsung batteries, which have the advantages of high energy ratio, light weight, small size, long service life, high safety, high voltage, and good consistency. The overcurrent protection value of the lithium battery is 15A, the maximum continuous working current is 2.2A, and the charging capacity is 2.2Ah, which fully meets the time and power requirements of the player. The specific design requirements are as follows.

1) Lithium battery model design requirements: 18650-3S1P/2.2 Ah/11.1 V.

2) Circuit design requirements.

1. 1.1.1.1.1.1 Single battery overcharge protection voltage: 4.35 & plusmn; 0.25V

2. Single battery regeneration overload protection voltage: 4.15 & plus 0.50V

3. Single battery overload protection voltage: 2.40 & plusmn; 0.08V

4. Single battery over-discharge recovery voltage: 3.00 plus 0.10V.

5. 10~17A

6. 70 and 5 minutes

7. The finished battery has short circuit and reverse charging protection.

3) Design requirements for battery cycle life: 300~500 times (national standard charge and discharge standards

4) Design requirements for battery size: refer to finished battery size

2. Schematic diagram of the design of the replacement lithium battery for a portable Bluetooth player.

1) Protection circuit board (PCM): This is mainly a protection circuit designed for rechargeable lithium batteries. Due to the chemical characteristics of lithium batteries, it is necessary to provide protection functions such as intelligent power calculation, overcharge, overdischarge, short circuit and overcurrent. In order to avoid dangers such as burning and explosion.

2) Protection IC (Protection IC): The main protection function chip in the design scheme, online monitoring of the battery's overcharge, overdischarge, overcurrent, short circuit and other functions , So that the battery can operate safely. , Stable and effective range.

3) Temperature switch: Mainly designed for temperature protection. When the temperature of the battery itself reaches the range of 70+5℃ due to other abnormal problems, the temperature switch will protect the temperature

4) 18650 lithium ion battery: /18650/2200 mAh/3.7V lithium ion battery (Samsung).

5) MOSFET: As a switch in the protection circuit, MOSFET will always prevent the voltage across the load from rising or falling to ensure voltage stability.

6) Battery packaging: shrinking PCV