03.Weld Penetration Depth Analysis
A battery pack is made up of battery cells welded together from terminal to terminal by metal tabs. The penetration depth of welding is a critical factor to ensuring safe and stable connection in the battery, especially for welding on the negative terminal. If the penetration depth is too light, then the connecting tab may fall off from impact, and if the depth is too deep, then the battery may be damaged in the process, causing an electrolyte leakage.
A simple optical inspection of the surface only provides limited information about the depth of the weld seam, smaller damages to the battery cell can easily escape notice. These small leakages will slowly accumulate and degrade the battery causing battery performance to deteriorate and increase safety risk.
Balancing the welding penetration depth is not an easy task, Kais utilizes many analytical tools to overcome this challenge, performing welding cross-section measurements to measure such items as the fillet welds, throat, leg lengths and penetration. Our research lab dissects and researches different combinations of battery cells and tab materials from various suppliers, adding that knowledge to our ever expanding database, and using these data as a guidance to weld with precision.
Front image of the weld point
Cross-section image of the weld point.
Image of melted zone between 0.09mm-0.14mm, 30% of the molten pool depth (acceptable parameter: 15%-50% of the molten pool depth).
Image of the heat affected zone (HAZ) penetrates the battery cell can (acceptable interval: complete penetration without deformation).
Reference: A study of weld penetration analysis of Tenpower INR18650-32ME