SPORTident now uses single-cell lithium batteries to replace BSF6 batteries instead of Alcaline triple cell packs as originally shipped. The lithium batteries last much longer than the original packs, and the voltage stays within range until almost the end of the battery’s life.
There are two aspects that need to be considered.
1) As stated elsewhere, there are three indications of battery well-being for lithium batteries. One is the actual battery voltage which is somewhere between 3.3V and 3.7V. A lithium battery maintains this voltage for most of the battery’s life, but then drops quickly off – but see #2) below. Furthermore the capacity indicator which is a computed value to approximate the remaining amount of ‘juice’ of the battery. Finally the actual battery installation date can also be a valuable indicator – if a battery has been in the system for over 4 years, then that needs to be considered as well.
2) Since the BSF6 units shut off almost completely (a magnet is needed to turn the unit on), there is so little current being used for the clock that the battery’s voltage eventually drops below 3V. This is not a concern though because unless the battery is near end-of-life, the voltage will quickly come up again once the unit is operating. But because of this voltage drop from non-use, the unit might beep 16 times to indicate a low voltage condition. If this occurs, let the unit run for a few minutes before shutting it off with the Service/Off key, and then turn it on again with the magnet. Typically the unit only beeps twice now to show that all is well! This also means you should not read the Voltage (using SI-Config) immediately after turning the unit on for the first time in a long while.