Date: 202109
Local time of day: 1801-2400
Location: ZZZ.Airport, US
Flight conditions: VMC
Weather elements / visibility: 10
Light: Night
Aircraft: Small Aircraft; High Wing; 1 Eng; Fixed Gear
Operator: Personal
Operating under: Part 91
Flight plan: VFR
Mission: Personal
Flight phase: Cruise
Airspace: Class D ZZZ; Class E ZZZ
ATC / advisory: TRACON ZZZ; Tower ZZZ
Aircraft component: Electrical Power
Component problem: Failed
Reporter organization: Personal
Reporter function: Pilot Flying; Single Pilot
Reporter qualification: Flight Crew Private
Human factors: Confusion; Distraction; Time Pressure; Troubleshooting; Workload; Communication Breakdown
Anomaly: Aircraft Equipment Problem Critical; Ground Excursion Runway
Detector: Person Flight Crew
When detected: Taxi; In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Overcame Equipment Problem; Flight Crew Requested ATC Assistance / Clarification
Contributing factors: Human Factors; Aircraft
Primary problem: Aircraft

Narrative: Cruising north from ZZZ1 at 4500 ft. MSL; I had just completed two take off and landings at ZZZ1. As we flew north (at approximately 340 degrees); 3-5 miles south of ZZZ2; I noticed that the dash lighting had begun to dim. Checked the amp/volt meter on the panel and noticed that voltage was at 12V and amps were reading -6.8 (from previous experience amperage runs at or close to 0 and volts run at about 28 volts). Noticed that the discharge light on the amp/voltage indicator was on. At this point; I cycled the alternator in the hope that doing that would solve the problem. I also verified that the breaker was still in. When the alternator was cycled and turned back on; the condition remained the same. At that point the GPS system shut off. Transponder was still functioning. At that point ZZZ Tower was called on the radio and the situation was described. ZZZ was told that we were unaware how much power remained to run the radio. At that point ZZZ Tower told me that our radio was cutting in and out. ZZZ was accommodating; they requested that we IDENT; they told me that they would contact ZZZ2 for us and clear all traffic for us enroute to ZZZ due to our NORDO condition. At that point we were also cleared to land on Runway XXL at ZZZ. During this time; the transponder showed an error message that it was not receiving power (or something to that effect); and I am not clear if the tower received the IDENT. Once permission to land was received (flying over ZZZ2) all unnecessary electrical systems (avionics; lights) were shut down to preserve any battery power needed for the radio once we neared ZZZ. Using major streets on the ground as checkpoints; we made our way to ZZZ. We flew left pattern to ZZZ and extended our downwind leg as we did not have adequate battery power to lower the flaps. On final approach attempted to turn the landing light on; however it did not come on. My flight companion had a flashlight throughout this so that we could monitor flight conditions on the panel (altitude; heading; etc.). As we came in for the flare we could not see the Runway centerline or the Runway number until just above the Runway (as it was dark and we had no lights). Touched down on the Runway XXL without incident and rolled down the Runway.At that point we turned on the radio and were able to communicate with ZZZ ground; their instructions were to take any Taxiway from the Runway. Exited at Taxiway XX However due to the closeness and the dim Taxiway/Runway lighting; inadvertently exited short and onto the grass separating Taxiway from Runway. Realized the error and my flying companion opened the window of the aircraft and used a flashlight to light up the Taxiway. Using the flashlight; we were able to make our way down the Taxiway until our parking area came into view. At that point we parked the aircraft and went to the gas shack at the FBO. Reported what had occurred to the fuel personnel and told them that the aircraft should not be put into service until maintenance had examined it. Next morning; first thing; I called the FBO and reported what had happened. They said that they had received the report from the fuel personnel and were in the process of canceling the morning's flights on the aircraft. I later received a call telling me that maintenance had discovered a wiring issue in the aircraft and that they were reconciling it.Just like to take the opportunity to mention that everything was executed well; the Tower was very helpful; we flew the plane without significant incident even though we had no functional electrical system. The only issue was that upon landing it was very difficult to negotiate the Runway/Taxiway due to dim lighting and faint Runway paint. The fact that the Runway and Taxiway lights are spaced the same also led to confusion as we were trying to negotiate them in the dark. After a difficult flight and a complicated landing; to think that negotiating the ground would be the most difficult part was stressful.




Synopsis: GA pilot flying at night reported complete electrical failure followed by a controlled landing then a runway excursion while turning off the runway due to the aircraft lights not working.