Yes, and these alone can be either a screwed back (either the whole back or some threaded ring), back screwed down with 4..8 screws, or simple pop-off. Tool needed depends on the watch, so general advice is difficult (lengthy). Simply put: you need a tool that fitsaladdin_sane wrote:I know there's watches where the whole back comes off....
Avoid ESD (electro static discharge):
Perfect is an earthed workplace with your wrist connected to it, there are special conductive wristbands for that purpose.
I stick to the following simple rules and have NEVER fried anything by ESD though I handle "naked" electronics every day:
- No woolen or synthetic clothing, chair upholstery, or carpet - this avoids electrostatic charge buildup in the first place and makes earthing rather unnecessary.
- Sit down and before you touch anything earth yourself somewhere. A power plug with only the earth contact connected is perfect for that purpose - of course at the beginning it's a strange feeling to touch the end of a wire that leads directly to a mains plug
No sweat on your hands. If you have sweaty hands, use thin cotton gloves.
Observe correct battery polarity.
Avoid handling batteries with metal tweezers, and if you do, be careful not to short them.
Dont try to sqeeze too thick batteries into a watch, it might break you module.
Be careful - don't touch or remove anything you don't have to.
You wrote "I know which sort of batteries I need", but I can't refrain from singing my song:
Use AgO batteries for LED watches.
In the long term, Silver Oxide is better than Alkaline for LEDs because they retain their 1.5V until the end. Alkalines decay from 1.5V down to 1.0V from the very first day, so the watch gets dimmer by time. The nominal capacity (mAh) isn't much different, but the voltage delivered.
Note that the Silver Oxides come in 2 flavours: low drain and high drain. High drain (KOH electrolyte) is obviously better for LEDs - it usually has "SW" ending, low drain "W" (Maxell code).
The only disadvantage is that the end comes almost without warning - only a few days after you notice it get s dimmer it finally dies.
Links to battery charts are here: http://dwf.nu/viewtopic.php?t=2583