Method for adjusting the methanol concentration in direct methanol fuel cells

Process for regulating the methanol concentration of a direct methanol fuel cell system having a fuel cell and a separate methanol reservoir comprises varying a first system parameter; and introducing methanol from a methanol reservoir depending on the resulting voltage from the fuel solution. An Independent claim is also included for a process for determining the methanol concentration in a direct methanol fuel cell. Preferred Features: Further system parameters are investigated before varying the first system parameter. A gas flow is increased during the variation. The current strength is varied in a determined region and a current-voltage characteristic line is acquired.