Abstract: The invention relates to a signaling system for use in a system for monitoring and/or controlling a stack of power cells. The stack of power cells is series connected, i.e. the negative terminal of one power cell is connected to the positive electrode of the adjacent power cell. A monitoring device is associated with each power cell to monitor characteristics of the power cell (temperature, voltage). Every monitoring device is powered by the power cell it is associated. The monitoring device monitors the status of the cell (e.g. it measures the difference of potential between the positive terminal and the negative terminal of that cell but it may also measure the temperature of the power cell, the pH of the electrolyte if the power cell Ci is a battery, etc. and communicates information on the status of the cell to other monitoring devices. The monitoring devices are daisy chained.