I need to change the battery on my fossil BG-2165

Fossil battery replacement sizes are usually a 2430 (CR2430), 371 (SR920SW), or 377 (SR626SW).
https://www.fossil.com/en-us/******/how-to-change-a-watch-battery

press and hold the button till it does something
most often buttons have a delay incase your wrist actuates it

It's actually a lot easier than that video shows. You're trying to represent a watch that is a PDA! To change the battery in your watch, you need to purchase a watch kit on eBay for about $15-$25, purchase the correct battery, watch a realistic video of changing a battery on Youtube, and then you will never need to pay more than the cost of a battery (a few dollars) to change your watch battery ever again! Sending it to Fossil takes time and money and you can do it at home with basic skills!

Who changed the battery, you or a watch repair serviceman? Did you replace the battery bar after you replaced battery? Did you check and see if there was a second battery (some watches have two)
You may need to have it serviced. Or try Fossil at :
http://www.fossil.com/en_US/shop/customer_care/static/fossil-Instructions.html

mcdevito75 here, Look for any Notch in the cover that match a notch in the case, use a knife with a sharp blade and place the knife in the notch and with a slight twisting motion the cover should pop off. Depending on the age of the watch and the functions cost could be anywhere betwwen $25.00----$60.00 Fossil watches are also collectables.

You could buy a watch case press or take it to a watchmaker. Does the back belong to this watch? I recommend a new seal with the removal of the back.

to change the battery of fossil blue watch,just open the case back and remove the old battery,look the number size on the battery and put a new battery that same number size ,after replacing battery press the case back tight to avoid water damage !good luck

Hello, not much help I'm afraid, but I was wondering where you intend to get the replacement battery for the 'tic' part? I'm trying to avoid sending it to Fossil.

I imagine your fault would be covered by warranty, and you get 2 years as well I think?

Try the following link: http://www.fossil.com/webapp/wcs/stores/servlet/StaticView?langId=-1&storeId=12052&catalogId=10052&page=Instructions&nav=custCareNav

There are several different Big Tic instructions available.