On November 15, 2017, about 2007 eastern standard time, a Cessna 172RG retractable gear airplane, N6102R, sustained substantial damage during landing at Miami-Opa Locka Executive Airport (KOPF), Miami, Florida. The airplane was registered to South Florida Aviation Group, LLC and operated by the pilot as a visual flight rules flight under the provisions of 14 Code of Federal Regulations Part 91 when the accident occurred. The certificated commercial pilot and safety pilot were not injured. Dark night, visual meteorological conditions prevailed, and no flight plan had been filed. The pilot reported that the purpose of the night flight was to practice instrument approaches for an upcoming Certified Flight Instructor Instrument check ride. Just prior to intercepting the glideslope for the ILS 9L approach into KOPF she moved the landing gear selector to the down position, verified that the landing gear position indicator light was illuminated green, set the flaps to 20 degrees, and completed the before landing checklist. About 500 feet above ground level (AGL), the GPS blinked, and all electrical power and radio communications were lost. The safety pilot set the transponder to squawk 7600. About 150 feet AGL the lights on the airplane's instrument panel blinked and remained illuminated. The pilot then selected flaps to 30 degrees and configured the airplane for landing, while the safety pilot attempted to contact the ATC tower. The pilot stated that she then moved the landing light switch to the on position, and immediately lost all electrical power. After receiving a green light gun signal from the tower, the pilot continued the approach and visually verified that the main landing gear was extended. Upon touchdown the right main landing gear collapsed, and the airplane departed the runway and sustained substantial damage to the right horizontal stabilizer. The pilot stated that no electrical or landing gear warning lights were illuminated for the duration of the flight. The safety pilot reported that they were inbound on the ILS 9L approach into KOPF. About 1 to 2 miles before the final approach fix they selected gear down and completed the before landing checklist. The GPS then began blinking on and off; however, she still had power to the airplane's radios. She set the transponder to squawk 7600 and attempted to contact the tower on the number two radio but was unable to establish communications. Shortly thereafter the GPS came back on, and she once again unsuccessfully attempted to contact the tower. She said the pilot then moved the landing light switch to the on position, and all electrical power was lost. She felt the airplane touch on the landing gear, and then the airplane began to sink and drift to the right. She stated that the landing gear was down, and it had been verified with the illumination of the landing gear position indicator light. According to the pilot operating handbook (POH) the landing gear extension, retraction, and main gear down lock release operation is accomplished by hydraulic actuators powered by an electrically-driven hydraulic power pack. A normal operating pressure of 1000 PSI to 1500 PSI is automatically maintained in the landing gear system. The nose gear and main gear incorporate positive mechanical down locks. Two position indicator lights are provided to show landing gear position. The landing gear system is also equipped with a nose gear safety (squat) switch, an emergency extension hand pump, and a gear-up warning system. A postaccident examination revealed that the airplane's battery had been depleted. Further examination revealed no anomalies with the landing gear system or its actuators. However, when the landing gear position indicator light was pressed or the gear was in transit, the landing gear unsafe horn did not produce an audible warning. The engine, while still mounted on the airplane, was operated under the direction of the NTSB IIC. The engine started normally without hesitation or stumbling in the observed rpm. While the aircraft was at idle rpm the ammeter indicated a slight discharge. However, the low voltage warning light did not illuminate. The engine rpm was then increased to about 1700 and the ammeter indicated a charge. An electrical load was then place on the system by turning on the landing light, strobe lights and rotating beacon, and the ammeter continued to indicate a charge. An examination of the low voltage warning light revealed that one of the wire's conductors that transit the instrument panel was completely severed but no evidence of burning or arcing was present. The closest weather reporting facility was Miami-Opa Locka Executive Airport (KOPF), Miami, Florida. At 1953, an METAR from KOPF was reporting, in part: wind from 020 °at 5 knots; visibility, 10 statute miles; clouds and sky condition, clear; temperature, 75 °F; dew point 70° F; altimeter, 29.93 inches of mercury.