Patent ID: 8617767
Filing Date: 2013-12-31
Classification: H01M,Y02E

Abstract:
1. A system for measuring and adjusting fuel concentration of a fuel cell stack comprising a fuel cell stack with a plurality of fuel cells and fuel solution reservoir, a mean for applying a direct current to one or more fuel cells of the fuel cell stack, a means for applying an alternating voltage directly to one or more fuel cells of a fuel cell stack, a means for measuring alternating current impedance of one or more fuel cells of the fuel cells stack following application of the alternating voltage, a means for measuring direct current of one or more fuel cells of the fuel cell stack following brief periodical load interruptions, and a means for adjusting methanol or water content of the fuel cell stack by adding either pure methanol or water to the fuel solution reservoir based upon the AC impedance and DC measurements, wherein lower AC impedance as compared to AC impedance at an optimal concentration of 1M methanol is indicative of a lower methanol concentration in the fuel cell stack and a need for addition of methanol to the fuel solution reservoir, while a higher AC impedance as compared to AC impedance at optimal concentration of 1M methanol is indicative of the methanol concentration in the fuel cell stack exceeding an optimal concentration of 1M and a need for water to be added to the fuel solution reservoir, and wherein lower voltage transient as measured by DC as compared to an initial open cell voltage is indicative of lower methanol concentration in the fuel cell stack and a need for methanol to be added to the fuel solution reservoir while higher voltage transient as measured by DC as compared to an initial open cell voltage is indicative of methanol concentration in the fuel cell stack exceeding the optimal concentration of 1M and a need for water to be added to the fuel solution reservoir.