US Patent 7855031 Method of making bipolar plate with coolant channels

Bipolar plates in a fuel cell stack tend to experience lower operating temperatures near and at the ends of the stack, and these plates require lower coolant flow. But common stamping tooling can be used to make all of the plates for the stack when suitable coolant flow restrictors are stamped into each plate for lowest coolant flow. The flow restrictors are then trimmed (or their formation avoided) from those plates designated for higher coolant flow.