Relay contacts stuck
C9. Apparent loss of battery capacity.
Electrolyte level too low.
Charging rate too low in aircraft.
Too little usage or shallow discharges.
C10. Complete failure of battery to operate.
Loose or brokenlead.
Loose or disengaged terminals in battery.
Battery not charged.
Cell open internally.
C11. Below normal battery output.
Battery switch left ON.
Voltage regulator set too low.
Internal connection links loose.
External connector burned or pitted.
Defective or reversed cells.
Cell case current leakage.
C12. External power fails to energize aircraft system.
Defective or incorrectly polarized external power source.
Defective external power receptacle.