An electrochemical device includes at least one electrochemical cell having an anode electrode and a cathode electrode, a reservoir configured to store an electrolyte and a mass distribution measuring device. The mass distribution measuring device includes at least one of a scale, a first pressure sensor located in a lower portion of the reservoir and a second pressure sensor located in an upper portion of the reservoir, or at least one strain gauge or load cell configured to measure a change a weight of the at least one electrochemical cell.