Narrative:

The aircraft was level at FL450 and we were conducting the cruise checklist when the pm (pilot monitoring) noticed that the battery voltage on the left side was amber and indicating 30V. The voltage indicator on the captain side indicated between 30V and 31V and was fluctuating. All other indications were normal. There were no illuminated cas (crew alert system) messages. The crew discussed possible courses of action and reviewed the checklists. Crew noted battery temperature on the left was slightly higher than the right and was slowly increasing. The crew contacted maintenance control and relayed the observations. Maintenance control had no specific actions for the crew; indicated that they would research the fault and recontact the crew.crew noted battery temperature was continuing to increase and that the cabin wash lights; cockpit flight guidance lights and numerous other switch-lights were flickering at a high frequency. The crew elected to reduce load by turning off nonessential cabin lights and cabin equipment. The rate of battery temperature increase was increasing so crew consulted batt 1 or 2 overtemp checklist. The checklist indicated that the battery switch should be selected off on the affected side. The crew discussed this option and decided; in an abundance of caution; to isolate the battery as per the checklist.when the battery switch was selected off; the PF (pilot flying) lost all flight data and the #1 IRS (inertial reference system) went offline. Multiple other electrical related cas messages illuminated indicating a cascade electrical failure. Also; the aircraft began to rapidly depressurize. The pm noted the cabin rate was indicating maximum climb and elected to don the oxygen mask shortly followed by the PF also donning his mask. Shortly afterwards the red cabin altitude cas message illuminated and the cabin altitude was noted to peak around 13;000 ft and stabilize. The pm contacted ATC and communicated that the aircraft had a pressurization issue and was beginning a descent shortly followed by [advising ATC] and conducting an emergency rapid descent. The flight controls were transferred to the right seat pilot due to the instrumentation loss. The left seat pilot again reviewed the checklist but there was no obvious cause of the abnormality. The pressurization remained steady at 13;000 feet for a period of time and then began descending slowly. The decision was made as a crew to divert to the nearest suitable airport which was determined to be ZZZ based on required distance to descend. The aircraft was landed safely.

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Original NASA ASRS Text

Title: Cessna Citation X flight crew reported an anomaly with the #1 battery charging system led to turning the affected battery off. This resulted in multiple electrical and pressurization issues; and a diversion to the nearest suitable airport.

Narrative: The aircraft was level at FL450 and we were conducting the cruise checklist when the PM (Pilot Monitoring) noticed that the battery voltage on the left side was amber and indicating 30V. The voltage indicator on the Captain side indicated between 30V and 31V and was fluctuating. All other indications were normal. There were no illuminated CAS (Crew Alert System) messages. The crew discussed possible courses of action and reviewed the checklists. Crew noted battery temperature on the left was slightly higher than the right and was slowly increasing. The crew contacted maintenance control and relayed the observations. Maintenance Control had no specific actions for the crew; indicated that they would research the fault and recontact the crew.Crew noted battery temperature was continuing to increase and that the cabin wash lights; cockpit flight guidance lights and numerous other switch-lights were flickering at a high frequency. The crew elected to reduce load by turning off nonessential cabin lights and cabin equipment. The rate of battery temperature increase was increasing so crew consulted BATT 1 or 2 OVERTEMP checklist. The checklist indicated that the Battery Switch should be selected off on the affected side. The crew discussed this option and decided; in an abundance of caution; to isolate the battery as per the checklist.When the battery switch was selected off; the PF (Pilot Flying) lost all flight data and the #1 IRS (Inertial Reference System) went offline. Multiple other electrical related CAS messages illuminated indicating a cascade electrical failure. Also; the aircraft began to rapidly depressurize. The PM noted the cabin rate was indicating maximum climb and elected to don the oxygen mask shortly followed by the PF also donning his mask. Shortly afterwards the red CABIN ALTITUDE CAS message illuminated and the cabin altitude was noted to peak around 13;000 ft and stabilize. The PM contacted ATC and communicated that the aircraft had a pressurization issue and was beginning a descent shortly followed by [advising ATC] and conducting an emergency rapid descent. The flight controls were transferred to the right seat pilot due to the instrumentation loss. The left seat pilot again reviewed the checklist but there was no obvious cause of the abnormality. The pressurization remained steady at 13;000 feet for a period of time and then began descending slowly. The decision was made as a crew to divert to the nearest suitable airport which was determined to be ZZZ based on required distance to descend. The aircraft was landed safely.

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.