Over the years Victorinox changed the battery installation. In earlier years the small battery was the CR-1025. Newer small batteries is the # 389. Larger knives (such as the traveller take the CR-1225. Also check as some the larger knives take more than one battery.
Note: The best way to ensure the correct replacement battery is first to remove the battery from your tool and order an exact replacement based on the number on the battery itself, and how many (some of the larger knives use 2 battries)..
(NOTE:Some models over the years have changed batteries, depending on the year of manufacture).
Replacement battery for, Swisslight , All 2¼ (58mm) knives that have a battery, Silver Tech Signature Lite
Replacement battery for All 2¼ (58mm) knives that have a battery, Wagner Swiss Pens.
Battery Replacement for Altimeter, Voyager, Voyager Lite, Spartan Lite, CyberTool Lite).(some take more than one battery)