Nearly all lithium batteries are required to pass section 38.3 of the UN Manual of Tests and Criteria, to ensure the safety of lithium batteries during shipping.
UN/DOT 38.3 Transportation Testing for Lithium Batteries 5th edition was issued in 2009, with Amendment 1 in 2011.
It includes eight sections. Sections T1-T5 use the same samples, and are tested in order. All primary and secondary cells and batteries are subject to these sections. Sections T6-T8 have more limited applicability. Following is a basic primer:
T1 – Altitude Simulation
This is low pressure testing that simulates unpressurized airplane space (cargo area) at 15,000 meter altitude. After storing batteries at 11.6kPa for >6 hours, these criteria shall be met: no mass loss, leaking, venting, disassembly, rupture or fire, and voltage within 10% of pre-test voltage.
T2 – Thermal Test
This test covers changes in temperature extremes from -40C to +75C. Batteries are stored for 6 hours at -40C (12 hours for large cells/batteries), then 6 hours at +75C (12 hours for large cells/batteries), for a total of 10 cycles. Testing may be performed in a single chamber or thermal shock chamber, but less than 30 minute transitions shall be used. Same pass criteria as T1.
T3 – Vibration
This test simulates vibration during transportation. Test is a Sine Sweep: 7Hz – 200Hz – 7Hz in 15 Minutes; 12 Sweeps (3 hours); 3 mutually perpendicular axes. Same pass criteria as T1.
T4 – Shock
This test also simulates vibration during transportation. Test is a Half-Sine pulse: 150G/6ms for small cells/batteries; 50G/11ms for large cells/batteries; 3 pulses per direction; 6 directions (+/-z, +/-x, +/-y). Same pass criteria as T1.
T5 – External Short Circuit
This test simulates an external short to the terminals of the cell or battery. At temperature of +55C, apply short circuit (<0.1ohm) across terminals. Maintain at least an hour after sample temperature returns to +55 +/-2°C. Pass criteria are: Case temperature does not exceed +170°C and no disassembly, rupture, or fire within 6 hours of test. Fuse, current limiting circuit, and venting mechanism activation are allowable.
T6 – Impact
This test is only applicable to primary and secondary cells. For cylindrical cells >20mm diameter, it simulates impact to case of cell. For cylindrical cells <20mm diameter and all other cell constructions, it simulates crushing of a cell. Pass criteria for any type is: Case temperature does not exceed +170C & no disassembly or fire within 6 hours of test.
T7 – Overcharge
This test is for secondary or rechargeable batteries only. It simulates an overcharge condition on a rechargeable battery: 2x the manufacturer’s recommended charge current for 24 hours. Then battery shall be monitored for 7 days for fire or disassembly.
T8 – Forced Discharge
This testing simulates a forced discharge condition for primary and secondary cells only. Same pass criteria as T7.
Per 126.96.36.199, in the event that a cell or battery type does not meet one or more of the test requirements, steps shall be taken to correct the deficiency before the cell or battery type is retested. Partial retest is not allowed.
Last month, MET Labs attended a CTIA Battery Certification Program meeting in San Antonio, Texas. The agenda included a review and update of the certification program documents (CRD, PMD, CRSL). There was also a discussion to expand the program to include battery life testing. In attendance were all the system vendors, CTIA-Approved Test Labs (CATLs) and carriers such as Verizon and AT&T.
Some of the key updates made in the Certification Documents were:
- The manufacturing location as well as the entity controlling the design of the battery shall both meet the ISO 9000 requirements.
- System or cell operating outside its temperature or voltage range shall be shut down and not allow 911 calls.
- CTIA will adopt the definition of coin cells in UN 38.3 to define the appropriate battery chemistries that can be considered under IEEE 1725.
- Adapters shall be compliant with USB-IF Battery Charging Specification Rev 1.2 and OMTP1.1 to avoid compatibility issues (and slow charging rates) between different OEM chargers and devices.
- Burr control will be harmonized in CRDs for both IEEE 1625 & 1725.
- Battery identification is required for both embedded and user-replaceable battery packs.
- Battery packs installed in its host and normal application of the device is above head level, the drop height shall be 1500mm; for all others the drop height shall be 1000mm.
There was also a proposal to include battery life testing mainly for smart phones. The proposal included creating a working group to develop an accurate battery life test standard for smart phones that will cover the following parameters:
- User profile
- Network settings
- Device settings
Read more about the CTIA Battery Certification Program in this previous post.
In March, MET Labs attended a CTIA Battery Certification Program meeting at Verizon Wireless in Bridgewater, New Jersey. The meeting was attended by carriers (AT&T and Verizon), CTIA-Approved Test Labs (CATLs) and a few vendors. The focus of the meeting was to address pending issues and update the battery certification program requirements and management documents.
CTIA manages a program to permit operators and their suppliers to validate a lithium ion battery’s compliance with the IEEE Standard for Rechargeable Batteries for Cellular Telephones, IEEE Standard 1725 – 2011, and the IEEE Standard for Rechargeable Batteries for Multi-Cell Mobile Computing Devices, IEEE Standard 1625 – 2008.
Some of the main discussion points were as follows:
The temperature sensing device (e.g. thermistor) will be tested to ensure it meets the manufacturer or the battery pack vendor stated temperature range. The purpose of this validation is to ensure that a thermal sensor either in the battery pack and/or host monitors cell temperature and works with the system to limit operation within the cell’s safe thermal specifications. This is to mitigate potential hazards, such as shutdown, or disabling of charging and/or discharging, or other protective action.
The test voltage for ESD will be at the minimum level 2 (2Kv or 4KV) and can also be higher (e.g. 8Kv) depending on the battery casing material.
CTIA will revise and clarify procedures for site evaluation to ensure all CATLs follow the same guidelines for site evaluations. CATLs will evaluate systems, subsystems and manufacturing sites using criteria set forth in the certification requirement document (CRD) in accordance with the applicable version of the Certification Requirement Status List (CRSL).
For non-embedded packs, the worst case test condition shall be used for testing.
Coin Cell Inclusion
IEEE 1625 and IEEE 1725 will be reviewed to include coin cell batteries in the program.
A new section in the Program Management Document (PMD) covers issue resolutions and challenges regarding site recognition or certification. The introduction of this section will mean the validity of site recognition or a certification of a product could be challenged by another CATL or Vendor. If a challenge is successful, the operator members of the CATL review committee may place the CATL or Vendor who was challenged on probation, suspension or revocation, depending on the severity of the findings.
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