Battery powered back up lights in the Operating Room of a hospital.
We have tested our battery powered back up lights in the OR as required monthly for the past several years. We have changed the batteries before recommended 10 years and during testing they work appropriately. They come on immediately once the breaker turns off the power. Our problem is, last week we had a situation where the power went out in the hospital and the back up battery powered lights did not come on in the OR . Again we did testing and they worked. Anyone have any ideas as to why or how this could happen.