Battery systems are designed to provide back-up supplies during power outages. Since a discharge test is nothing other than a simulated power outage, there is no risk of battery damage. Batteries can normally be deep discharged (that is, discharged to the manufacturer’s end-of-discharge voltage) between 100 and 1,000 times, depending on the type of battery.
Using a few of these discharge cycles for capacity testing has a negligible effect on overall battery life. Nevertheless, there is no reason to carry out discharge testing more frequently than recommended by the relevant standards.