I own a Traser H3 (P6500-x model) and the battery died. I figured I could fix this on my own, so that's what I did. Battery information can be found at the end of this post. My watch takes a type 371 battery. Traser claims you should not attempt this on your own because it could jeopardize the waterproofing --but these watches are not that sensitive. When the watch is disassembled for battery replacement, there will be parts to keep track of. There is the watch itself, the back cover, a white plastic insert to hold everything in place, a rubber 'O' ring, the four screws, a battery and of course the band retaining pin and strap. Here's How To Change The Battery Yourself: The cover on the back of the watch has 4 tiny screws, easily removed with a small set of screwdrivers. There's a simple rubber 'O' ring underneath the cap, just remember to place it in its groove properly before resealing. You will need to gently remove the white plastic insert to get to the battery. The battery pops out easily with gentle persuasion from a small standard screwdriver: Be certain you are careful when you pop out the battery. The retaining arm for the battery is just to the side, and it can be bent or broken: REASSEMBLY: Be careful when you insert the battery --do not force it! You want to slide it carefully down and into the channel. It should pop right in with a little wiggle from a finger to fully seat it. Do not press down hard! The battery will not go into place with force. Again, slide it down easily, as shown below: Here is a close-up of the rubber 'O' ring. Be certain it is in its proper channel before reassembly: Replace the cover, tighten screws properly. If you have any concerns or doubts --please take your watch to a jeweller or professional! BATTERY TYPE / INFO: Model 6500 takes a type 371 battery Model 6502 takes a type 395 battery Link to battery chart listing: Watch Battery Cross Reference at Battery Info Waterproofing: The Traser H3 is not exactly "waterproof", fit for diving --but you could remedy this yourself or have it sent out to Traser for pressure testing and proper sealing. You could use a sealant (LINK) in small amount to ensure it will seal. I hope this helps.