mkove electronics

Coulomb Counting


Coulomb counting is simply measuring and counting the current flowing into and out of a battery. It is the method that battery monitors normally use to estimate the State of Charge.


You might wonder why not count the watts, or the power flowing into and out of the battery to make the process more accurate - the reason is that a battery is a chemical process. It is the current, or amps, flowing into and out of the battery that is most directly related to the chemical reaction and the battery does not care about the Volts it is providing.


The problem with coulomb counting is that it is not very accurate.[1] For a short period of time it will provide some accuracy but over longer periods it does not totally reflect the chemical reactions that might also be occurring from recent cycling of the battery, from temperature variations or from changes in the chemistry or structure of the battery. Even just movement of the battery can change the stratification of the electrolyte or change the activation of various parts of the cell plates thereby changing theavailable capacity.




[1] Wikipedia. State of Charge.