When we had our life raft repacked/certified at that same time, we had them remove the out-of-date EPIRB [batteries past their shelf life, and no internal GPS...] and replace it with a much smaller, waterproof, freshly dated [6 year battery shelf life] PLB with built-in GPS.
To be prudent, we investigated the cost of replacing the battery in the outdated McMurdo / Pains Wessex SOS Rescue 406 EPIRB that we had removed from the life raft.
At US$250 plus shipping both ways, we decided to toss it because we can buy a new, modern EPIRB with GPS and a 10 year battery life for about US$100 more than the replacement battery...
This decision left us with an old EPIRB to dispose of. Since there was no USCG base near us at the time, we went online and found the original manual which included disposal instructions. The two options were to either remove the battery and recycle appropriately, or remove the antenna, wrap the unit in metal foil [to prevent signal transmission] and set it off to drain the battery...
We decided to fire off the unit to observe the battery runtime and prevent activation in the future.
This EPIRB had already been declared inactive in the NOAA registration database, but we wanted to make sure and not contribute to the already prevalent false alarms. Therefore we decided to follow the manufacturer's instructions for running the EPIRB without the antenna, but instead of wrapping it in aluminum foil, we put it in our stainless steel oven [solid door; i.e., no glass] and fired it off. [...the EPIRB, not the oven...]
We started the test at the top of the hour- the designated time period for testing PLB and EPIRBs- just in case...
As you might expect, the xenon [not LED as in more modern EPIRBS; i.e., bigger drain on battery...] strobe started flashing immediately, and the other lights indicated it was faithfully attempting to transmit the emergency signal.
No phone calls were received, nothing was heard on the VHF radio, and no rescue boats or helicopters showed up so apparently we were successful attenuating the signal.
Since the unit was 7 1/2 years past the original [5 year shelf life] battery expiration date, we didn't expect it to last for long. Therefore we peeked in the oven every ~4 hours to see if the strobe was still firing and the other lights still indicated it was transmitting...
These units are specified to meet the EPIRB standards of transmitting for a minimum of 48 hours at -4°F. [The ambient temperature inside the boat averaged 65°F during the testing period.]
We continued checking every few hours [4-6 times each day] and after 4 days the unit was still transmitting.
It finally died sometime around the 4 1/2 day mark. [~108 hours] We left it in the oven another 24 hours just in case the battery came back to life after a rest... it didn't...
Who cares? Well, we're naturally curious, and we found this test encouraging.
To summarize: this older model EPIRB [without GPS] with batteries 7 years and 7 months past their expiration date still ran more than twice as long as the minimum required period [48 hours with non-expired batteries...]
What does this mean to us? When the batteries expire in our current and future EPIRBs, we will keep them onboard and actively registered for a couple of additional years as back-ups to their replacement(s).
This is based upon the assumption that battery technology keeps improving, and if the older lithium batteries delivered the performance documented above, newer battery technology/formulations will likely be equal or better.
Will we bet our lives on it? Nope! [Nor are we recommending anyone else does either...]
The key word here is back-up; we will always carry at least one in-date, modern EPIRB on the boat, and likewise an EPIRB or PLB packed in with the life raft, and we always have PLBs on our person- on the boat and on land.
That means as of this writing we can fire off 5 NOAA registered emergency beacons in case of an emergency. [Our written plan is to do this in succession- not simultaneously- in extenuating circumstances; possibly using the out-of-date units first if it isn't an abandon ship emergency. If a beacon fails to transmit, then fire off another...] Bump that count to 6 once we replace our current EPIRB later this year... [Update Dec-2016; New 10 year EPIRB added to inventory.]
But we all know SOPs and reality can vary in times of crisis... At least the odds are in our favor that one of these buggers ought to work if/when needed...
Here's hoping none of us ever have a need for our emergency beacons...
- Emergency Alert Devices [blog post]