Lithium batteries are difficult to test...
“Any safety device that you’ve bought to save your life in a ‘worst case scenario’ should be treated with the utmost respect,” explains Peter Forey, Managing Director of Surrey-based Sartech. “You understand what it does, when you need to use it – you trust it with your life. Yet some people will still ignore critical information about the battery life in their documentation. After all, you just pushed your EPIRB’s ‘test’ button, the light came on, so it’s working perfectly, right?”
The truth is batteries are manufactured from chemicals that break down over time. They will even degrade without being used and the rate of deterioration depends a lot on the ambient temperature. In most cases replacement is required after 5 years to ensure that there is enough capacity remaining to give the necessary operating time.
With regular alkaline batteries (see Fig. 1), it’s pretty easy to determine how healthy they are because they decay steadily with time, as illustrated when switching a torch on and getting a progressively dimmer light. Mobile phones batteries are more complicated, in-phone software monitors your usage and charging history to predict how much battery charge you have left, but it’s still just a best-guess.
However, with primary lithium batteries (the type of power source used in most EPIRBs) their decay is non linear (see Fig. 2). No ‘fuel gauge’ has ever been developed to accurately measure Lithium cells, and their chemical composition makes it very difficult to determine how much battery life is actually left. Even years after manufacture the terminal voltage may remain relatively high, but there is no way of determining where you are in the battery’s lifecycle or how much longer this voltage will remain stable enough to operate the device.
Paranoid pushing of the ‘test’ button will simply decrease battery life further. To ensure that your EPIRB will work perfectly when you need it most, it is best to operate the “test” function no more than once a month and to get the EPIRB serviced in accordance with the device’s guidelines. “But, just like your car, you don’t have to go back to the manufacturer and prepare yourself for a hefty bill,” explains Forey. “Sartech is a Registered Shore Based Maintainer and we are qualified to maintain all makes of SART and EPIRB.”
“It’s probably going to be OK to take a gamble on the best-before date on that tin of tuna that’s been knocking around in the galley for three years; but don’t apply the same mentality to the one thing on your boat that could ensure your safety when you need it most. If the worst happens and you do get into trouble at sea, we guarantee you will not be thinking about the money you saved by not servicing your EPIRB,” concludes Forey.