Tolerance compensation systems for high-voltage batteries

The most important in a nutshell:

• Tolerance compensation systems are crucial when connecting the high-voltage battery to the car body in order to prevent deformation and achieve an optimum joint pattern
• A universal screw connection for the internal connection also makes it possible to remove and install individual cell modules
• Saving heat conduction medium can save costs, extend battery life and improve performance

Battery connection of the high-voltage storage unit

High-voltage batteries, which are used in the electrified automotive industry, are rigid components with very high tolerances that have to be connected to the body. The high-voltage battery is a very sensitive component. Even a minimal distance between the contact surfaces can lead to unequal bending forces and stresses during assembly.

The bodywork, on the other hand, is comparatively susceptible to torsion, so considerable deformation of the bodywork and impairment of the gap dimensions and joint patterns can already occur during installation. Tension-free attachment of the battery to the vehicle underbody is therefore crucial for flawless quality.

WITOL has developed particularly robust tolerance compensation systems for the battery connection. The WITOLs are preassembled either on the battery housing or on the vehicle body. In the bolting process, the tolerances are compensated in the axial direction. By means of suitable slotted or square holes and sufficiently large screw heads, even compensation radially to the screw axis is possible.

Internal connection of the individual battery cells

The internal connection of the individual cell modules to the battery housing is also subject to tolerances. If the component is screwed together conventionally, the tolerances between the cell modules and the cooling base are usually compensated for with cost-intensive heat-conducting medium. This leads to poorer heat dissipation and higher vehicle weight. In addition, high compressive stresses can occur, which lead to deformation and insufficient thermal management of the high-voltage battery.

With the same active principle that is already used for the external connection of the high-voltage battery, WITOL tolerance compensation systems equalize the gap between the cell module and the housing flange without stress. The negative effects that arise in the conventional bolting process are thus effectively eliminated. The use of a universal screw connection also makes it possible to remove and install individual cell modules during servicing.

Optimum performance through efficient use of coolant

But WITOLs also address a completely different point. They serve not only to fix but also to reduce the liquid gap filler in the battery. To ensure optimum thermal conductivity, the coolant must therefore have full-surface contact with each cell module at all times and also precisely compensate for the unevenness of the housing base.

With the WITOL tolerance compensation system, the cell module is pressed into the final position, displacing the coolant. This ensures full-surface contact of the cell module at all times and unevenness no longer needs to be filled by adding coolant. This also applies when only a small amount of liquid gap filler is available. As a result of the tolerance compensation, a smaller amount of coolant is required, which leads to significantly improved thermal conductivity. This increases performance and prolongs the service life of the battery. The reduced use of liquid gap filler also means that high costs can be saved in the long term.

Special features at a glance

Recognize the advantages of WITOL tolerance compensation systems:

• Flexible use: Our tolerance compensation systems can be used for any type of assembly. Even if it becomes necessary to replace individual cell modules or even the entire housing of the high-voltage battery, installation and removal can be carried out without any problems. This is possible due to the universal screw connection.
• Innovative installation: The automated feeding of the systems as well as the automatic bolting enable fast and safe installation with the lowest possible degree of contamination.
• Saving of liquid gap filler: With the use of WITOLs, the cell modules can be precisely fixed to make the layer of coolant as thin as possible. This demonstrably reduces the amount required.