When are non-rechargeable batteries of an emergency locator transmitter (ELT) required to be replaced?

• A. When 50% of their useful life expires
• B. After 2 years regardless of life
• C. Whenever the ELT is serviced
• D. Only after an incident requiring use of the ELT

Answer: (A)

Non-rechargeable ELT batteries have a finite useful life, and we replace them before that life runs out to keep the beacon reliable in an emergency. The standard rule is to replace the battery when half of its useful life has expired. That halfway point provides a safety margin so the ELT can still deliver adequate power when needed, since performance degrades with age even if the unit isn’t used.

Replacing after a calendar period, such as two years, isn’t guaranteed to match the battery’s actual remaining capacity, so some batteries would be replaced too early and others too late. Replacing only during servicing or only after an incident isn’t necessary and could leave the beacon unreliable when it’s most needed.