Do you mean constant potential experiment ? If yes, generally the current will decrease upon time flow. The particular shape of the curve varies with first of all active material of the electrode, but also with e.g. history of the previous cycling. The capacity of the electrode is an integral of current after time (within a potential range not leading to the presence of overcharging). The above is valid in the ideal case of current efficiency equal unity (no parasitic reactions present). usually the amount of charge withdrawn form the electrode is lower (significantly in first cycles) the the amount delivered.

In normal practice we used to do galvanometric charge discharge for battery performance as well as for reporting the results. So current density ( unit mA/g) is the current that is applying ( withdraw in case of discharge) to the cell, now if we multiply the current density with the charging time (in Hours), then we can get the acheived capacity (unit mAh/g) of the material (cathode of anode) so charging time = practical capacity / current density.

we should use chronopotentiometry for  charge - discharge test.

then we  convert the potential - time curve to the potential - Special density diagram