Intermittent discharging of nickel–metal hydride secondary battery

A nickel–metal hydride secondary battery is discharged intermittently through a switch of 30 s on/30 s off mode via an external load R _r. The discharge current i _g is measured during switch-on and an open-circuit voltage V _oc during switch-off. In the course of discharge run, i _g drops at some time by depletion of an active material within the positive electrode. The pulse shapes of i _g and V _oc in each on/off duration are featureless before the i _g drop, satisfying the relation V _oc=i _g(R _i+R _r) (R _i being the internal resistance of a battery). After the i _g drop, they become time dependent; yet, the above relation still holds. It is found that V _oc changes continuously through the onset times of switch-on and -off.