Definition
A battery servicing procedure in which a storage battery is fully discharged and then fully recharged to restore its capacity. Deep cycling is used on nickel-cadmium (Ni-Cd) batteries to reverse the gradual loss of usable capacity that occurs when the battery is repeatedly subjected to shallow charge/discharge cycles.
Plain English
Running a battery all the way down and then charging it all the way back up, on purpose, to bring its full capacity back.
Context Anchor
Seen in aircraft battery maintenance, electrical system discussions, and battery condition checks.
Derivation
‘Deep’ here means going all the way to the bottom of the battery’s charge, rather than only partway. ‘Cycling’ refers to one full discharge-and-recharge cycle. So a deep cycle is a complete down-and-up swing, as opposed to the small partial swings that happen during normal use.
Why Pilots Care
Maintains battery capacity and reliability for engine starting and emergency electrical power.
Grounding Statement
If an aircraft battery is drained nearly empty and then charged back up, that is one deep cycle.
Intuition Check
“Deep” does not mean physically deep inside the battery. Here it means the battery has been discharged far down from full charge.
Example Sentence 1
The Ni-Cd battery was removed from the aircraft and sent to the shop for deep cycling after its capacity check fell below the limit.
Example Sentence 2
Deep cycling is scheduled every few months on turbine aircraft to prevent memory effect in the batteries.