A spokesman for Parker LORD said battery developments could reduce the number of required components by up to 40 percent, but could be more prone to drop damage and problems during repairs.
In a recent webinar presented by EV Charged magazine, technology researcher Tim Fornes explained that OEMs are increasingly interested in moving from so-called cell-to-module (CTM) battery designs to cell-to-board (CTP) technology. Parker Lord is one of the companies developing new adhesives and sealants to make new technologies work.
According to Fornes, CTPs offer many advantages over CTMs, primarily in terms of weight savings and increased energy density, which are key drivers for electric vehicles but also have many disadvantages.
Most OEMs or their suppliers are currently using CTM technology to manufacture battery packs, he said. In this method, individual battery cells are combined into modules that are attached to aluminum cooling plates. Each module can contain from a few to dozens of units, depending on the design.
This structure requires two different gap fillers with different properties. The first is a low-strength adhesive that is used between the battery and the module. This filler, usually a silicone material, but sometimes a two-component polyurethane, is required so that the elements can be removed from the module for repair without damaging any of them. It must also conduct heat to transfer the heat generated by the battery.
A second gap filler, usually two-piece polyurethane, connects the module to the cooling plate. This requires a strong bond for structural integrity as well as thermal conductivity, according to Fornes.
Both fillers must be flexible enough to withstand the shock and vibration of the vehicle while maintaining extreme temperatures for 10 years or more. They must also resist delamination, which affects thermal conductivity.
The CTP structure excludes modules. Instead, the battery is glued directly to an aluminum cooling plate. This has huge advantages in battery electric vehicle (BEV) designs, according to Fornes, as it enables lighter weight and higher energy density — essentially more battery power for the same volume.
Fillers used in CTP technology must provide structural strength and thermal conductivity, and must also be able to withstand environmental factors.
Fornes says CTP technology can reduce parts count by up to 40 percent because it eliminates not only modules, but a certain number of wires and electrical connectors called busbars. This will reduce the cost of production and, at least in theory, reduce maintenance costs.
It will also give designers more freedom to choose the size and shape of individual devices, Fornes said.
Without modules, CTP also provides fewer “interfaces” through which the heat generated by the battery must pass, improving cooling.
According to Fornes, there are drawbacks to CTP technology. One of the problems that repair crews can face is the strength of the connection between the battery and the cooling plate in case the battery needs to be removed. “Removing these batteries and replacing them is not an easy task,” he said.
Fornes also noted that CTM provides better battery protection in the event of a crash and keeps the battery electrically isolated to prevent “thermal runaway” that can start a fire when the heat generated inside the battery pack exceeds the amount of heat dissipated to the environment. . . . CTM can also monitor and control individual battery modules.
Parker LORD develops sealants that provide a strong and flexible connection between a polyethylene terephthalate (PET) wrapped battery and its aluminum cooling plate. PET is mainly used to provide an extra layer of electrical insulation for batteries to prevent sparks.
The company’s scientists say that through shear testing, including 1,000 hours of aging at 85 percent relative humidity and 85 degrees Celsius (185 degrees Fahrenheit), the company has developed a new thermally conductive adhesive that it believes will work in harsh environments. Susan Donaldson.
The next step, according to Donaldson, is to further improve the material’s properties and adapt the technology to other materials such as electronically plating materials and nickel-plated steel.
In the long term, she said, the company will work on a battery-chassis configuration in preparation for the “next generation of technology.”
For more information on the development and testing of CTP fillers, see the Parker LORD white paper LL3253-TCAdhesives for Cell-to-Pack.
https://www.lord.com/content/whitepaper-thermally-conductive-adhesives-for-next-generation-cell-to-pack-configurations
Post time: Nov-15-2022