from chemistry to pack
Busbar Joint Failure Modes and Contact Resistance This is a worked example accompanying Failure Mode and Effects Analysis (FMEA) in Battery Design. It works through a pack-level DFMEA line on a bolted busbar joint, a component that is mechanically simple but disproportionately responsible for field failures because it sits at the intersection of high current, … Read more
Choosing between aluminium and copper is one of the first decisions in any busbar design. Both materials are capable conductors, but they make very different engineering trade-offs. This page sets them side by side across the properties that matter most — electrical, mechanical, thermal, and practical. Material Properties at a Glance The table below compares … Read more
When we consider the battery thermal management system we need to start with the basics and look at the heat sources and paths in a battery pack. We don’t have to minimise all of these sources of heat, but it is important that we carefully consider them all. It is important to calculate 1. Cell … Read more
There are so many things to think about in any busbar bolted joint design. Hence it is useful to look at examples and experience. One of the most comprehensive resources in this field is the “Copper for Busbars Guidance for Design and Installation” by the Copper Development Association [1]. The Electrical Power Engineering Reference & … Read more
Copper surface corrosion is an important subject when considering copper busbar joints. When copper is exposed to air and moisture, it forms a thin layer of reddish-brown copper oxide and other corrosion products. These products are not as conductive as the copper, leading to increased resistance at the joint. The increased resistance leads to local heating … Read more
Cylindrical cells are commonly joined using several methods, each with distinct advantages and disadvantages depending on the application. Here are the most popular methods: Spot Welding Description: Spot welding uses a controlled electrical current to create localized heat, fusing a nickel strip to the positive and negative terminals of the cells. World Electr. Veh. J. 2018, 9(2), … Read more
The Electric Vehicles Clinic just released details of the Tesla Model 3 cell busbar failures. This is such an important topic that we thought we should cover these findings for the battery design community. In the Tesla Model 3 with the 21700 cell based battery packs the cell connections are single side and the connections … Read more
Can we build a quite simple cell busbar thermal model? First thoughts are whether we can make some simple approximations and hence create a spreadsheet model. We have a current [I] flow through the busbar (orange). The busbar has a resistance defined by it’s resistivity, cross-sectional area and length. Hence we can calculate the heating … Read more
Relaxation in bolted busbar joints can be a significant battery durability issue. As joints relax the resistance of that joint increases, resulting in larger voltage drops and excess heat generation in the joint. The relaxation of the joint can be the result of a number of mechanisms: Stress Relaxation Stress relaxation is a function of time, … Read more
Is there a relationship netween weld mechanical and electrical properties? The basic conclusion is that low electrical resistances were found to correlate with high mechanical strengths of the welds. Correlation between electrical resistance and tensile strength for welds produced with (blue markers) and without (red markers) spatial beam oscillation. [1] This post has been built … Read more