My ACK ELT hit the 10 year replace the Duracell CR2 or equivalent Audio Alert battery. I must confess to paying more attention to the ELT test signal on my Yaesu handheld when I do my every 3 month or so ELT Test than I do to the solitary beep the contraption makes after the Yaesu sounds off. As a consequence, I don’t know exactly when failure happened. When I opened the unit, I was surprised to see leakage from the lithium Duracell, with corrosion of the + terminal and spilling over onto a couple of the SMD components. I was able to solder in a copper strip to repair the terminal, but unfortunately, there was so much damage I had to order a new Audio Alert, $42 plus shipping and tax from AC Spruce & $11 for a new CR2. All back to working and not too bad, pricewise.

I have had numerous Duracell alkaline batteries destroy hardware before, so much so that I don’t use those or unknown name brands any longer, but I’ve never had a lithium battery of any sort do that before. Anyway, I switched to a Energizer Ultimate Lithium, and will probably just replace them every 5 years instead of the 10 years listed, and I will promise the airplane to pay more attention to the “beep”. FYI

PS: The main ELT battery is due to be replaced this summer. The least expensive I’ve found is about $275. Those are getting pricey!