capacitor is made up using the 25 h 2 so 4 as the highly acidic electrolyte of the prior art for the purpose of comparison in table i electrolytes at five levels of ph are listed and the effect of each ph level on the properties of the capacitors is recorded from the above table it can be seen that the leakage current characterizing the double layer capacitor with higher ph electrolyte is an order of magnitude less than that of the highly acidic electrolytes as to capacitance it can be said that while the capacitance is somewhat lower than that of the prior art double layer capacitors nevertheless the capacitance remains at a highly useful level regarding the equivalent series resistance of the units a slight increase in resistance is noted at the higher ph levels but the slightly increased resistance of such units is regarded as tolerable in that it does not seriously affect the function of the capacitors as indicated the above test results were obtained on single cell capacitors in order to achieve higher voltage ratings a plurality of single cell units are stacked with the current collector elements of each unit cell in contact with the next adjacent units the test results presented in table ii were obtained using capacitors each assembled by stacking six unit cells as described above the stacked cells are 34 canned 34 in an inner insulating liner and an outer metal container various electrolytes of the invention at ph levels from 4 2 to 9 9 are used in assembled double layer capacitors the activated carbon used in the electrodes is either apl carbon or pwa carbon both available from calgon results obtained in essentially identical structures with the highly acidic.