Definition
An undesired flow of electrical current backward from the battery into the generator, occurring when the generator's output voltage drops below the battery voltage. A reverse-current cutout relay is used to disconnect the generator from the battery in this condition to prevent the battery from discharging through the generator and to protect the generator from damage.
Plain English
Electricity flowing the wrong way in an aircraft's electrical system — from the battery back into the generator instead of from the generator into the battery. A protective switch automatically disconnects the generator when this happens.
Context Anchor
Seen in aircraft electrical-system discussions, especially around generators, batteries, and reverse-current protection.
Derivation
From Latin reversus, 'turned back,' and currens, 'running.' The term literally means 'current running the wrong way' — which is exactly what it describes in the electrical system.
Why Pilots Care
Uncontrolled reverse current drains the battery and can damage the generator or other components, so protective relays automatically open the circuit when it is detected.
Analogy
It is like water flowing backward through a pipe. The pipe may still be full, but the flow is going the wrong way for the system to work properly.
Intuition Check
Do not read “reverse current” as just a switch being set to reverse. It means the electric flow itself is moving opposite the intended direction.
Example Sentence 1
When the generator's voltage dropped below the battery's, the reverse-current cutout relay opened to prevent the battery from discharging back through the generator.
Example Sentence 2
During preflight, the pilot confirmed the reverse current relay would protect against battery discharge if the generator failed in flight.