In an interview that PreSafe had with Kimberly Kelly, board member of the National Association for Search and Rescue, she pointed out that you need to have at least three days to find and rescue someone who has wandered. And the statistics bear that out.
The likelihood of serious injury or worse is 50% after 24 hours, 70% after 48 hours, and 90% after 72 hours.
So, a personal rescue beacon, in additional to telling their families and caregivers whether their loved on has been put into extreme weather or has had a serious fall, need to continue signaling the family and community about where the person is for at least 72 hours after the warning notifications have sounded.
As a warning, most generic GPS trackers run out of battery power after one or two days of continuous use. And, sadly, some organizations misrepresent how long their batteries last -- sharing only the length of time their battery will last when their device is not in rescue mode.
A battery that powers a personal rescue beacon will need a minimum of 72 hours of operation after a warning alert has sounded.
So, to reiterate, a battery that powers a personal rescue beacon will need a minimum of 72 hours of operation after a warning alert has sounded. But, as life happens, accidents don't usually take place at optimal times (like having just finished recharging a battery). Instead the opposite is too often the case—where your loved one has come into harm's way the very day that the battery was due to be recharged (at about half power).
Thus, and importantly, in addition to the 72 minimum hours needed for a recharge, the personal rescue beacon will have to carry a charge long enough to work between charges, and then have an additional minimum 72 hours to spare.
The other realistic factor for battery life is that many adult children of parents diagnosed with Alzheimer's live nearby, but are not visiting their parents every day. Many times, the visits take place only on the weekends. So, designing the device to work with a once per week, or once every two weeks recharge, is necessary.
And with all those things in mind, this is how we built PreSafe…