Replace battery on Casio DB-36-1AV - Casio DB36-1AV Wrist Watch

https://support.casio.com/storage/en/manual/pdf/EN/009/qw2515.pdf

https://support.casio.com/storage/en/manual/pdf/EN/009/qw2515.pdf

The back has to come off in order to replace the battery. To loosen the stuck screw wet the tip of a cotton swap/Q-tip with WD40 (don't overdo it) and press it on the screw so that it seeps in between the screw and the back plate. Let it do its work for some 10 minutes and try to turn the screw. Use a watch maintenance screwdriver that fits well to prevent damaging the little screw.

There is a clip over the battery and then down on one side. You need something tiny and sharp... like a needle. You can insert the needle into the clip between the battery and the outside edge of the clip and gently pry the clip out and away from the battery.

mcdevito75 here, This can be very, very tricky on a Casio watch, Casio"s have an LCD liquid crystal Diode in the face and any un-do pressure on the face will break it. Best Bet, look for a small watch repair shop in your area to change the battery, a small shop will save you some money on the cost.

It may be that the watch is working in one of the "settings"modes.

If you do not have any instructions you can get them from their web site.

Go to the casio web site "casio.com".

Select "support" and the "manuals", watches;

Accept terms

Select "watch manual archive"

Read the number of the back of your watch and enter it into the search box

This may have a reset button inside the back , maybe marked a.c. if it does you need to short it with metal tweezers between the battery and the a.c. button.
hope this helps

The cover is removed by prying, - there should be a small notch on the back, just be careful!

Visit this site:

http://world.casio.com/wat/download/en/manual/

Enter the right numbers from the caseback and download manual for your watch.
Don't forget to rate, please.

Change battery

If your databank is like mine (DB-35H), there is a TINY spring in a really unusual spot that you probably didn't notice that fell out. Laying the watch face down and with the back off, there is a little tiny hole in the back towards one of the corners. (sorry, already put my watch back together and didn't notice which corner.) There is a tiny (1/16" x 1/4") spring that sits upright in that hole. It must make a contact with the metal cover. I replaced my battery and when I did, a spring fell out. I looked all over the internet, then wrote Casio, who said they didn't have access to the information about where the spring went. (Doh!) I got a used DB-35H from my brother and was going to swap the innards when I noticed the spring on his. Put my spring back and it beeps! If you've lost the spring, don't know if you can fake it with tinfoil or not, but it really is a TINY spring. Good luck.