Battery replacement for a G-shock.

The reset trick works with other Casio Alarm Chrono digital watches, such as my old Model W-720, as well. After the new lithium coil cell is installed and secured with the spring clip, the watch may show random segments in the LCD display or may simply be blank. Insert a sewing needle, paper clip, or blade of a small jeweler's screwdriver into the hole on the back of the movement stamped "AC" (All Clear) to momentarily connect the gold plated contact at the bottom of the hole to the stainless steel battery clip. The battery clip in most such Casio watches is connected to the "+" terminal of the coin cell. This will reset the CMOS chip and it should start up with the watch displaying 12:00 and the date at 1-1. Then, use the control buttons to set the time and date in the normal fashion.

It means you need to "short" the watch for it to strat back up.

Thanks guys, the two solutions above worked with a Casio TRT-500. I have to play with a few exposed contacts to get the right connection as the AC was not properly marked. Saved me the cost of a new watch!

Take a paper clip put one end of it into a hole labeled AC and the other end labeled ground (gnd or -) (not + as stated in your post). You need to externally complete the circuit before the watch display will turn on. Also watch how you install the back plate. It may only go in one direction (to complete circuits for some of the switches).
Good luck

It is marked as (+) on some models

Thank you! =)

How to replace ctl1616 battery in casio g shock