The detector is a portable industrial nondestructive testing instrument.It can test,locate,evaluate and diagnose multiple defects in the workpiece quickly, without damage and precisely.It can be widely used in the fields of manufacturing, iron and steel, metallurgy, metal processing, chemical industry and so on.Also widely used in aviation, aerospace, railway transportation, boilers, pressure vessels and other fields of in-service security inspection and life assessment.It is necessary for NDT industry.Portable flaw detector has become an important tool for field testing in modern society.So,Provide efficient, portable and sufficient back-up power for portable flaw detectors,is an important guarantee for testers to perform long-term on-site work. Because of its own unique advantages, 18650 lithium battery has become preferred backup power solutions of such high-tech testing instruments.

Design requirement

I. Design requirements of standby lithium batteries for flaw detectors:

Because of the high voltage and long working time of the flaw detector, the quality of the equipment itself and the stability of the power supply are critical. ，This requires that its power supply must be realized by the multi string and combination of high-capacity single cell lithium batteries; In the process of the flaw detector, a great deal of valuable data needs to be kept，Therefore, the battery must provide accurate power display and alarm system to prompt the user to keep the data in a timely manner, so as to improve the effectiveness of the work. An intelligent chip is adopted for the standby lithium battery program of the flaw detector, whose host reads the smart chip power and related important data through the I2C communication way, in order to prompt the user to conduct relevant operations in a reasonable and timely manner. The SANYO battery cells in our solution have the advantages of high energy ratio, light quality, small volume, high cycle life, high safety, high voltage, good consistency and so on. The specific design requirements are as follows:

1）solution requirements for lithium battery models：18650-3S2P/5000mAh/11.1V

2）solution requirements for circuit parts:

1、Single cell overcharge protection voltage: 4.35±0.25V

2、Single cell overcharge recovery voltage: 4.15±0.50V

3、Single cell over discharge protection voltage: 2.40±0.08V

4、Single cell over discharge recovery voltage: 3.00±0.10V

5、Battery pack overcurrent protection value（10ms）: 30~35A

6、Battery pack over temperature protection value (recoverable): 70±5℃

7、The finished battery also has short circuit and reverse charge protection.

3）Solution requirements for cycle life of batteries：300~500 times（National standard for charge and discharge）

4）Battery size design requirements: refer to the battery shell

Ⅱ. Design scheme of spare lithium battery for flaw detector:

1）Intelligent electric meter protection board（PCM）: uses SBS intelligent battery management system, uses the advanced calculation principle of electric energy to calculate the battery power accurately and always, and reports battery power to host via SMBUS at any time. Meanwhile, perform functional protection on rechargeable smart battery packs. Because of its chemical properties, the lithium battery needs to provide intelligent power calculation, overcharge, over discharge, short circuit, over-current and over temperature protection functions to avoid fire, explosion and other hazards.

2）18650 lithium ion battery cells: /18650/2500mAh/3.7V Li-ion cell（SANYO）

3）Temperature switch: mainly aims at the temperature protection function design. When the temperature of the battery itself reaches 70 ± 5 ℃ due to other abnormal problems, the switch is switched off automatically to protect the temperature.

4）MOSFET: In the protection circuit, the MOSFET acts as a switch, so that the voltage at both ends of the load will not rise or decrease, and the voltage stability will be guaranteed.

5）Battery package: shell.

Ⅲ. Drawings and real pictures of battery products: