Narrative:

I took off out of ZZZ uneventfully. After several minutes a 'whooshing' sound developed very lightly in my headset. I tried to see if any instrumentation had an indication that aligned with the rhythmic sound in my headset. With no further indications of problems (no warning lights; no ammeter issues; no vacuum or oil pressure issues; I continued on to ZZZ1.after receiving ATIS at ZZZ1; I called the tower at 9.2 miles out to notify them of my intention to land at ZZZ1.I was asked to report a 2 mile left base for runway xx. At 4.2 miles on my GPS (approximately 2.5 miles out from an extended base leg; I notified tower that I was on an extended base to runway xx. With no traffic in the area; ZZZ1 tower cleared me to land for runway xx.almost immediately after I received the clearance to land and I acknowledged it; my instrument panel start to show signs of a power failure with the blinking of both my nav/comm radios and the loss of power to my portable avionics via the auxiliary/cigar lighter adapter. In an attempt to locate any issues; unplugged the adapter and left the portable avionics unpowered. I toggled the switch to the rotating beacon and began powering down the nav/com radios one at a time. Nothing improved the situation. The power plant continued to generate power; so being cleared to for landing and having the runway safely in sight; I continued my approach. I tried to put in flaps and noticed the motors sounding sluggish; so I stopped after 15 degrees of flap. The approach was normal and I landed safely on runway xx at ZZZ1. I turned off the first taxiway that was to my left about halfway down the runway and moved off the active and stopped with my tail safely off the runway. My instrument panel and nav/com radios were completely dead. I have two portable radios and found that the batteries for both portable units did not contain enough charge to power the radio. I took out my cell phone and opened up the AOPA airport app to see if I could locate the tower phone number; but it was not listed. I kept looking at the tower but my relative position to the tower was skewed and without moving the aircraft further; I could not see the tower for any light signals. My destination was [company] to drop my plane off for an avionics upgrade; so I did have the phone number of [company] on my phone. I called [company] and asked him to contact the tower and let them know of my dilemma. He said he would and I told him that I was going to cross the main taxiway and get on the service taxiway so that I would be in a position of less potential traffic conflict. I immediately proceeded to the service taxiway and proceeded to [company] without delay.upon arrival; [company] indicated that he called the tower and let them know of my issue.things I learned that I need to do before my next flight...1. Always research the phone number of the tower and have it close at hand 2. Test both portable comm radios before take off to assure that both are operational3. Study the far/aim for loss of communication procedures when on the ground[company] looked into the issue and found that the voltage regulator had failed and the recent start of the engine had caused the battery to drain and not be able to supply enough charge to keep the instruments alive until landing at ZZZ1.

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Original NASA ASRS Text

Title: Pilot reported electrical failure on approach to landing.

Narrative: I took off out of ZZZ uneventfully. After several minutes a 'whooshing' sound developed very lightly in my headset. I tried to see if any instrumentation had an indication that aligned with the rhythmic sound in my headset. With no further indications of problems (no warning lights; no ammeter issues; no vacuum or oil pressure issues; I continued on to ZZZ1.After receiving ATIS at ZZZ1; I called the Tower at 9.2 miles out to notify them of my intention to land at ZZZ1.I was asked to report a 2 mile left base for Runway XX. At 4.2 miles on my GPS (approximately 2.5 miles out from an extended base leg; I notified Tower that I was on an extended base to Runway XX. With no traffic in the area; ZZZ1 Tower cleared me to land for Runway XX.Almost immediately after I received the clearance to land and I acknowledged it; my instrument panel start to show signs of a power failure with the blinking of both my nav/comm radios and the loss of power to my portable avionics via the auxiliary/cigar lighter adapter. In an attempt to locate any issues; unplugged the adapter and left the portable avionics unpowered. I toggled the switch to the rotating beacon and began powering down the nav/com radios one at a time. Nothing improved the situation. The power plant continued to generate power; so being cleared to for landing and having the runway safely in sight; I continued my approach. I tried to put in flaps and noticed the motors sounding sluggish; so I stopped after 15 degrees of flap. The approach was normal and I landed safely on Runway XX at ZZZ1. I turned off the first taxiway that was to my left about halfway down the runway and moved off the active and stopped with my tail safely off the runway. My instrument panel and nav/com radios were completely dead. I have two portable radios and found that the batteries for both portable units did not contain enough charge to power the radio. I took out my cell phone and opened up the AOPA Airport app to see if I could locate the Tower phone number; but it was not listed. I kept looking at the Tower but my relative position to the Tower was skewed and without moving the aircraft further; I could not see the Tower for any light signals. My destination was [Company] to drop my plane off for an avionics upgrade; so I did have the phone number of [Company] on my phone. I called [Company] and asked him to contact the Tower and let them know of my dilemma. He said he would and I told him that I was going to cross the main taxiway and get on the service taxiway so that I would be in a position of less potential traffic conflict. I immediately proceeded to the service taxiway and proceeded to [Company] without delay.Upon arrival; [Company] indicated that he called the Tower and let them know of my issue.Things I learned that I need to do before my next flight...1. Always research the phone number of the Tower and have it close at hand 2. Test both portable comm radios before take off to assure that both are operational3. Study the FAR/AIM for loss of communication procedures when on the ground[Company] looked into the issue and found that the voltage regulator had failed and the recent start of the engine had caused the battery to drain and not be able to supply enough charge to keep the instruments alive until landing at ZZZ1.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.