At what depleted capacity percentage should substation batteries be changed out?

Batteries in substations are crucial for ensuring a reliable backup power supply. When assessing the need for replacement, a depleted capacity of 80% is often considered a critical threshold for changing out substation batteries. This is because at 80% capacity, the battery may not be able to sustain the intended load for the necessary duration during a power outage or during battery testing.

Operating a battery at this depleted state can lead to diminished performance, increase risks of failure, and potentially jeopardize the safety and reliability of the entire system. Therefore, changing out batteries at this point helps in maintaining optimal operating conditions and ensures that there is always sufficient power available when needed.

The other options represent capacity levels that are generally seen as still functional; however, they don't account for the risk and reliability factors involved in battery performance in critical applications like substations.