8D Quality Report of
18650 2000Mah-300 Battery Leakage
D1
Problem Description
Customer feedback: After spot welding nickel strips, one piece of the cap was found leaking. And after grouping, one piece of the cap was found leaking.
D2
Problem-Solving Team
Team made up of colleagues from Quality, Production, R&D Department.
D3
Root Cause Analysis
The leakage issue in one battery was confirmed. Subsequently, on-site analysis was conducted at the customer’s location.
3.1 The retained samples of our company was inspected and the size of the battery sealing position was measured. The outer diameter of the battery sealing is 18.14mm, meeting the process requirements. The sealing height is 2.42mm-2.47mm, also meeting the process requirements.
3.2 Airtightness compression test: Battery 1# is compressed at 0.6 MPa and maintained for 4 minutes without air leakage; Battery 2# is compressed at 0.6 MPa and maintained for 4 minutes without air leakage.
3.3 Disassembly and analysis of Battery 2#: Inspection of the appearance of the cap, steel cap, aluminum plate, and PTC revealed no damage or deformation, and measurements conform to the drawing requirements.
3.4 For Battery 1#, further analysis of the cap involves dissecting and examining the compression condition of the gasket.
Analysis of the cross-section of the cap #1 reveals a tight fit of the upper and lower compressed position gaskets with no leakage points.
a) The left and right compression ratios of the lower gasket are 50.2% (0.276mm) and 51.6% (0.284mm) respectively, meeting the compression ratio requirements.
b) The left and right compression ratios of the upper gasket are 72.2% (0.397mm) and 81.2% (0.447mm) respectively, with one point (0.447mm) slightly exceeding the compression ratio. Under extreme pressure conditions, this may lead to the discharge of internal gas from the battery, carrying electrolyte with it.
D4
Containment Action
4.1 Conduct a comprehensive inspection for liquid leakage after storing 2000PCS of batteries at -10°C for 4 hours.
4.2 Perform a thorough inspection of the assembled battery packs for any external leakage.
4.3 Upon passing both inspections, the battery cells can be shipped as usual. DLN Energy will provide a quality assurance letter.
D5
Potential Corrective Action
5.1 Contact the mold manufacturer to adjust the R-angle of the three-seal sealing mold, controlling the compression ratio of the gasket to 65±10%.
– This will enhance the battery’s pressure-holding capability.
5.2 Advise the customers to avoid using batteries that have been dropped and damaged during use, as dropped batteries carry a certain risk of leakage.
D6
Implement Corrective Action
6.1 The imaging device has arrived at the company. Subsequent sealing station first inspections (including initial production, after machine adjustments, and mold changes, etc.) will be conducted, and measurements of battery cross-sectional dimensions will be increased.
6.2 Modify the inspection procedures for the sealing process, adding a gasket compression check: Upper gasket compression ratio of 65±10% and lower gasket compression ratio of 50±10%.
6.3 During the battery turnover process, customers are advised to place cushioning pads on the ground to prevent damage from batteries falling and causing subsequent leakage issues.
D7
Take Preventive Action
After modifying the sealing mold, the gasket compression ratio has met the design requirements. Currently, the randomly sampled compression dimensions for the upper and lower edges after sealing are as follows:
7.1 The upper gasket compression ratios are 68.2% (0.375mm) and 70.4% (0.387mm), respectively.
7.2 The lower gasket compression ratios are 42.7% (0.235mm) and 51.1% (0.281mm), respectively.
D8
Closure & Team Celebration
The leakage issue with the batteries in question is considered an isolated case. DLN Energy has already modified the module to prevent liquid leakage caused by minor falls. It is recommended that customers refrain from using batteries that have fallen during the usage process. Based on a thorough analysis, we have ruled out any inherent issues with our battery cells.
For the Original Report Document, please contact us.