Swiss Army watches are known for their style and rugged durability. And like many watches, Swiss Army watches are designed to be opened with a proprietary wrench design rather than common tools. Authorized Swiss Army service centers and other watch service centers have these tools handy, but chances are that you do not. That leaves you with two choices: Take the watch to the pros or attempt to do it yourself with less-than-perfect tools.
Use the Victorinox Swiss Army website (see Resources below) to locate the authorized service center nearest you.
Take your watch to the nearest authorized service center. If there are no authorized service centers in your area, refer to the Victorinox Swiss Army customer service link for instructions on how to ship your watch to an authorized service center for battery replacement.
Request battery replacement.
Collect your watch after the battery has been replaced.
Lay the watch face down on a flat rubber surface. This should keep the face of the watch from getting scratched, but the rubber will also provide some grip so that the watch won't turn while you're turning the plate on the back.
Locate the two notches on the back of the watch plate. Open a pair of needle nosed pliers so that the points are about as far apart at the notches and stick one point into one of the notches. Then adjust the pliers as necessary as you push the other point down into the other notch.
Apply some pressure on the pliers, pressing straight down toward the work surface. Slowly turn the pliers around to the left, using them like a wrench.
Unscrew the back plate in this method until it is loose enough for you to finish unscrewing it by hand.
Locate the battery, which will be the only loose part inside the watch. Take note of the direction the battery is facing, then turn the watch over to dump the old battery out.
Put the new battery back in facing the right direction. Replace the back plate and turn it to the right until it is finger tight.
Lay the watch face down on the rubber again. Use the pliers to tighten the back plate just as you used them to loosen it.