Electric vehicles, which include fuel cell vehicles, must meet the standards for high-voltage components. To keep vehicles safe, a minimum insulation resistance of the electrically conductive components to the vehicle ground (earthing) must be maintained.

Through the coolant, however, the bipolar plates of the fuel cell stack may be linked electrically to earthed neighboring components. For this reason, the solubility of ionic components in the coolant circuit of fuel cell stacks may create a problem, as it increases conductivity. This causes electrical short-circuit effects and power losses of the fuel cell, which may lead to the entire system shutting down.

Over the service life of a fuel cell, various ions may penetrate the coolant circuit. The ions may be created, for example, by the coolant interacting with the various cooling system materials and by the aging or decomposition products of the coolant itself.

Insulation resistances from fuel cell stack to adjacent grounded components when ion exchanger is arranged parallel to coolant pump.