I did something similar once. I un-did the velcro and left the battery on the battery plate. Then I picked up the helicopter off the ground and the battery fell off. It has a dent similar to yours and has exhibited no problems since the incident (6 months ago). I have not flown it (and never will), but it has been ok for some bench tests. As a PARCAP member I agreed to this safety policy as well: 2.6. The PIC is responsible for checking that all flight batteries are at a proper level of charge to ensure safe flight. Any battery that is exhibiting any signs of distress will not be used for flight. Any battery that has, to the PIC’s knowledge been dropped or subjected to any form of mechanical impact shall not be used for flight. Any battery that has, to the PIC’s knowledge, been inappropriately over-discharged, or over-charged shall not be used for flight.