All wildlife photography requires a great sensitivity to the animal and a respect for the subject of your photograph. Just as with a portrait of a person, you would not want to make your subject feel uncomfortable so it should be with any photo of wildlife. If the animal is disturbed, or forced to leave the area, then the picture is simply not worth it. Any action which causes the bat to abandon a favourite feeding place, or a safe roost, can make the difference between life and death for that animal.
Bats present some special issues for the photographer. Firstly, they are a highly protected species which it is illegal to disturb in any way. By implication this limits bat photography to those photographers who hold a bat licence and who have a reason to photograph a bat as part of a study or recording project.
Bats are creatures of the night – they are extremely sensitive to light. For this reason, I chose never to use flash preferring an LED ring light or a moment of illumination from a torch. Better still is if you can get your picture using a very high ISO. Some cameras will work in almost total darkness. See Bats at the Forge photos taken at dusk on 25,000 ISO.