Challenges In Developing Interconnect Technologies For Evs & How To Address Them

India is the 5th largest car market in the world & has the potential to become one of the top three in near future with 400 million customers in need of mobility solution by 2030. The country needs a transportation revolution. The transition to electric mobility is a promising global strategy for decarbonizing the transport sector. India is among a handful of countries that supports the global EV30@30 campaign, which aims for at least 30 percent new vehicle sales to be electric by 2030.

To meet this target, Interconnects technologies from a key spoke in the wheels of EVs deployment. Interconnects can be mainly categorised into Power Interconnects, Signal Interconnects apart from the other segments. Power Interconnects consists of molded Busbars, phase busbars & motor stator busbars. The Signal Interconnects include the power connectors, modules and assemblies & power connection systems, the main function of all these Interconnect solutions is for carrying current, signal to and from the various vehicle systems, like motor, battery, ECU, cooling system, steering system, and more.

In the design, development & manufacturing of the above various interconnect solutions, various challenges are faced by designers and the engineering faternity. We can focus on some of the considerations in the battery interconnects. For any part engineers need to consider the most important a scpects Form, Fit & Function into their design.

Function:

Electrical Performance:

1. Interconnects must be designed in a way to have shortest current path from most +VE to most -VE. This is to minimize Joule heating effect of Current Collector Assembly.

2. Interconnects must be able to carry specified continuous & Peak current.

3. Battery Interconnect System to must be designed to have no resistance imbalance across conduction path. To achieve this, Current Collector Assembly must be designed to have uniform current density.

4. Battery Interconnect System needs to be kept under specified max. Temperatures and as much as possible, it needs to have uniform temperature distribution across conduction path and lowest ΔT from most +VE to most -VE.

5. Selection of Material is an important criterion to achieve function, we ldability with cells that drives cost.

6. Cell level fusing (maximum safety) is the most challenging part of Battery Interconnect System applications & Design.

Mechanical Performance:

Battery Interconnect System to be able to withstand Vibrations and shocks offered by various driving conditions.

Fit:

Battery Interconnect System needs to be fit within the space constraints provided by battery pack manufactured. Often this will be conflict with electrical performance and cost. There will challenges to fit Battery Interconnect System within boundary conditions that meet Electrical, Mechanical performances and cost targets. If Current Collector Assembly is welded both +VE and -VE on same side of a cell, the challenge is to separate them to avoid short circuit at all operating conditions and provide sufficient dielectric strength.

Form:

Current Collector Assembly design needs to be able to weld with cells. Achieving intended weldability ensure greater electrical performance of the battery pack. Limitation on the thickness of the Current Collector Assembly due to weldability factors calls for careful consideration of the material thickness that is compatible for welding method chosen.

Manufacturing:

Challenges in manufacturing remain mostly same as general manufacturing practices, but as the process includes stamping, cleaning, welding, molding, assembly, and others, special focus needs to be given to the cleanliness aspect as any oil contamination will impact the weldability of interconnects between Copper & Nickel and welding with the cells.

Quality of the stamping and welding needs to be monitored for burr free parts & consistent welds. Based on our experience we find the start-ups very aggressive on the design aspects, but when it comes to design for manufacturability, they get stuck and must fall back on experienced players in this field.

To support the start-ups & customers, we have established our development team who based on our manufacturing, design & development expertise get involved at the initial stages of development with the start-up designers and help them consider the manufacturing aspect of the interconnects to reduce the iterations & shorten development lead times. This also helps them to evaluate the cost & optimise during the development stages of their projects.