Definition
An electrical instrument that measures and displays the total amount of electrical charge that has flowed into or out of a battery over time, expressed in ampere-hours. It tracks the running balance between current drawn from the battery and current returned by the charging system, giving a continuous indication of the battery's state of charge.
Plain English
A gauge that keeps a running tally of how much electrical energy has gone into and out of the aircraft's battery, so you can see how full or empty it is.
Context Anchor
Seen in aircraft electrical-system and battery discussions, especially when checking battery use, charging, or remaining battery capacity.
Derivation
The name describes exactly what it measures: amperes (the unit of electrical current) multiplied by hours (the unit of time). One ampere flowing for one hour equals one ampere-hour of charge moved.
Why Pilots Care
Confirms the battery holds enough stored energy to start engines and run essential avionics without unexpected power loss.
Analogy
It is like tracking how many gallons of fuel have been used, not just how fast fuel is flowing right now.
Intuition Check
Do not read ampere-hour as just amps. Amps describe the rate of electrical flow; ampere-hours describe the amount accumulated over time.
Example Sentence 1
During the preflight check, the pilot noted the ampere-hour meter showed the battery was nearly fully charged.
Example Sentence 2
Before departure the pilot noted the ampere-hour meter reading to ensure adequate reserve for the planned flight.