Date: 201908
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Flight conditions: VMC
Weather elements / visibility: 12
Light: Daylight
Aircraft: Piper Single Undifferentiated or Other Model
Operator: Personal
Operating under: Part 91
Flight plan: None
Flight phase: Cruise
Airspace: Class E ZME
ATC / advisory: Center ZME
Aircraft component: DC Battery
Component problem: Failed
Reporter organization: Personal
Reporter function: Pilot Flying; Single Pilot
Reporter qualification: Flight Crew Private
Human factors: Confusion; Situational Awareness
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Landed As Precaution; Flight Crew Landed in Emergency Condition; Flight Crew Returned To Departure Airport; Flight Crew Overcame Equipment Problem; General Flight Cancelled / Delayed
Contributing factors: Aircraft; Human Factors
Primary problem: Aircraft

Narrative: After takeoff; I was headed east on a 090 radial at an altitude of 2500 ft.  I selected the HDG (Heading) button on my autopilot and ALT (Altitude) hold at 2500 ft.  3 to 4 minutes later the ALT hold starts a sharp climb then does a sharp dive.  I disconnected the AP (Autopilot) and scanned all my instruments looking for any abnormality that would indicate why the AP Altitude select would have gone out.  None of the instruments on the panel indicated anything wrong.  I continued on my flight and turned to a northerly heading and proceeded in that direction for approximately 10 minutes.  Turning back to the west to get in a position to turn south and land; I tried the AP again on HDG.  It worked fine holding the heading. Then I tried the ALT hold and it immediately started going up and down.  Again I disconnected the AP; and noticed a flashing low voltage signal on my EFIS (Electronic Flight Instrument System). While observing the EFIS; the voltage dropped from 8 volts to 7 volts and was continuing down.  Recognizing the battery was failing; I powered down the GPS to try and conserve as much of the battery as possible.  I called ZZZ to alert the traffic there that I may be coming in with no radios.  I flipped to the AWAS channel to get wind information to make runway landing determination from.  I switched back to the CTAF for ZZZ and gave the traffic in the pattern my landing intension.  I could hear another pilot in the area passing my calls on to Memphis Center but by that time my radios died from lack of power.  When I landed all my electronics except for my EFIS was dead.  I taxied to my repair shop and parked the plane.  I told [the] Mechanic that the battery had failed for some reason. He told me he would check it and get back to me. The Airport Manager arrived and asked me if I was flying the plane that called in with the battery failure and I told him I was.  He was on the phone with Memphis ATC at the time and told them I was down safe and at the repair shop.  He then called Houston ATC to relay the same information.  Evidently two planes flying in the area had passed-on my radio information to two different Centers.  The mechanic checking my plane found the battery had a shorted cell and would not take or hold a charge.  He replaced the battery and the problem was solved.  In retrospect; I should have paid closer attention to my amp meter and my volt meter on prior flights.




Synopsis: Cherokee 235 Pilot reported electrical failure and associated equipment failures inflight due to battery failure.