Prediction of remaining battery discharge time in telecommunications systems

A telecommunications power system is always equipped with a standby power source, usually rechargeable lead acid batteries. However, predicting the remaining discharge time during the course of actual battery discharge has not yet been attempted. The authors introduce and demonstrate a useful calculation method, in which the load current profile is divided into equal short time units. This allows the total reserve time of the battery to be calculated by deducting the integrated amount of electricity in ampere-hours from the available ones. Then, the remaining discharge time can be calculated by subtracting the elapsed time during AC failure. In the integration process, the amount in each time unit is transformed into a value equivalent to a 10-hour rate discharge by using the coefficient introduced in this study. This method is examined by applying it to several load current profiles including actual ones from telephone offices, and the results show prediction error to be +or-5%.<>