When it's time to change the battery in your Seiko watch, you need to replace it with the right type of battery so that your watch will work properly. You also need the right tools to open your watch: While all Seiko watch cases open at the back, some watch backs are fastened with screws and others can be pried off. The Seiko Company, which has been making timepieces since 1881, recommends using only official Seiko brand watch batteries.
Turn your Seiko watch over so the back is facing up.
Use a small screwdriver to remove the screws from the back of the watch case if it is screwed on. If the case has a snap-off back, carefully place the tip of a small flathead screwdriver underneath an edge of the casing and gently push up to loosen it. Remove the watch back and set it aside in a safe place, along with the screws if applicable.
Look at the battery inside the watch and note which side is facing you. Remove the battery by slipping the screwdriver under it and carefully popping it out, or turning the watch over and gently tapping the face until the battery falls out.
Purchase a new Seiko watch battery with the same number. Write down the number printed on the old battery or take it with you when you buy the new one. You can get Seiko batteries from an authorised Seiko dealer, a watch or jewellery store, or online retailers.
Put the new Seiko battery into your watch. Position it in the battery slot with the same side facing you as noted in Step 3, then press it down until it is firmly in place.
Replace the watch back by either snapping it into place or screwing it back on.