Research on Restrain on Thermal Runaway Propagation,
Runaway Propagation,

▍What is CTIA CERTIFICATION?

CTIA, the abbreviation of Cellular Telecommunications and Internet Association, is a non-profit civic organization established in 1984 for the purpose of guaranteeing benefit of operators, manufacturers and users. CTIA consists of all U.S. operators and manufacturers from mobile radio services, as well as from wireless data services and products. Supported by FCC (Federal Communications Commission) and Congress, CTIA performs a large part of duties and functions that were used to be conducted by the government. In 1991, CTIA created an unbiased, independent and centralized product evaluation and certification system for wireless industry. Under the system, all wireless products in consumer grade shall take compliance tests and those complying with the relevant standards will be granted to utilize CTIA marking and hit store shelves of North American communication market.

CATL (CTIA Authorized Testing Laboratory) represents labs accredited by CTIA for testing and review. Testing reports issued from CATL would be all approved by CTIA. While other testing reports and results from non-CATL will not be recognized or have no access to CTIA. CATL accredited by CTIA varies in industries and certifications. Only CATL which is qualified for battery compliance test and inspection has access to battery certification for compliance to  IEEE1725.

▍CTIA Battery Testing Standards

a) Certification Requirement for Battery system Compliance to IEEE1725— Applicable to Battery Systems with single cell or multiple cells connected in parallel;

b) Certification Requirement for Battery system Compliance to IEEE1625— Applicable to Battery Systems with multiple cells connected in parallel or in both parallel and series;

Warm tips: Select above certification standards properly for batteries used in mobile phones and computers. Do not misuse IEE1725 for batteries in mobile phones or IEEE1625 for batteries in computers.

▍Why MCM？

● Hard Technology: Since 2014, MCM has been attending battery pack conference held by CTIA in US annually, and is able to obtain latest update and understand new policy trends about CTIA in a more prompt, accurate and active way. 

●Qualification: MCM is CATL accredited by CTIA and is qualified to perform all processes related to certification including testing, factory audit and report uploading.

The thermal propagation of a module experiences following stages: Heat accumulation after cell thermal abuse, cell thermal runaway and then module thermal runaway. Thermal runaway from a single cell is not influential; however, when the heat spread to other cells, the propagation will cause a domino effect, leading to the thermal runaway of the whole module, releasing massive energy. Figure 1 shows the result of thermal runaway test. The module is on fire due to irresistible propagation.The heat conductivity inner a cell will be different according to different directions. The coefficient of heat conductivity will be higher in the direction parallel with the roll core of a cell; while the direction that is vertical to the roll core has lower conductivity. Therefore thermal spread from side to side between cells is faster than it does through tabs to cells. Therefore the propagation can be seen as a one-dimension propagation. As battery modules are designed for higher energy density, the space between cells is getting smaller, which will worsen thermal propagation. Therefore, suppressing or blocking the spread of heat in the module will be considered as an effective way to decrease hazards.
We can restrain thermal runaway actively or passively.Active thermal spread suppression is mostly based on thermal management system, like:1)Set cooling pipes on the bottom or the inner sides of a module, and fill with cooling liquid. The flowing of cooling liquid can effectively decrease the propagation.2)Set up fire extinction pipes on the top a module. When there’s thermal runaway, the high temperature gas released from battery will trigger the pipes to spray out extinguishant to suppress propagation.However, a thermal management requires extra components, lead to higher cost and lower energy density. There’s also possibility that the management system may not take effect.