Definition
Batteries that remain inert during storage and only begin producing electrical power once they come into contact with water, which acts as the activating electrolyte. In aviation, they are commonly used to power emergency locator transmitters (ELTs) and other survival equipment intended for use after a water landing or ditching.
Plain English
A battery that stays switched off until it gets wet. Water flowing into it starts the chemical reaction that makes it produce power.
Context Anchor
Seen in Emergency Locator Transmitter and emergency equipment inspection discussions, especially when checking whether a battery has been activated or needs replacement.
Why Pilots Care
They keep the ELT transmitting after a ditching, directly improving the odds of timely rescue.
Grounding Statement
Picture emergency gear stored dry in an aircraft; if it ends up in water after an accident, the battery can start supplying power without the pilot turning it on.
Intuition Check
Do not assume water is just something that damages the battery here. In this term, water is what starts the battery working.
Example Sentence 1
The life raft's locator beacon uses a water-activated battery, so it begins transmitting automatically once the raft is in the sea.
Example Sentence 2
Following the water landing, the water-activated batteries powered the ELT and guided rescuers to the site.