Residual Capacity Estimation of Stationary Lithium-ion Secondary Cells in Telecommunications Systems Using a Brief Discharge

Lithium-ion batteries are expected to contribute to miniaturizing power systems and prolonging backup times in telecommunications systems. From the viewpoint of maintenance, checking battery conditions automatically is desirable after the deployment of lithium-ion batteries to telecommunications systems. Estimating the residual capacity of backup batteries is one of our major concerns in maintaining them. To do this, we propose discharging lithium-ion batteries to an actual load for a short duration, measuring the voltages in this discharge, and estimating the capacity using the correlations between the voltages and residual capacities. We studied the fundamental correlations between the voltages during discharge and the residual capacities using trickle-charged single cells and a float-charged 14-cell series-connected battery in high-temperature acceleration tests. We found good correlations between the voltages and residual capacities in both the single cells and the battery. These correlations may be useful for estimating the residual capacities of float-charged lithium-ion batteries using brief discharges into actual loads.