As many Stalker v3’s are getting old, the RTC batteries may need to be replaced. First, measure the battery voltage to determine if replacement is needed, the nominal voltage for the CR1220 cell is 3 V, but the RTC may continue to be backed-up even if the cell voltage is 2.75 V or less. If replacement is required, remove the cell from the PCB by desoldering both tabs, then clearing the PCB holes with solder wick or a solder sucker. Note that the tabs on the cell are tack welded and cannot be removed. New CR1220 cells with tabs (Google “tabbed CR1220”) are available from a number of sources, including eBay. Make sure you get cells with the tabs oriented at 180 degrees. Solder in the new battery and your RTC will be like new.