Possible to change a Casio f-91w battery safely without special tools?

I only watched a quick video, seems like you need a tiny (PH00 or PH000 size?) screwdriver and some tweezers, didn't look particularly difficult?

A new watch costs £4 or so on ebay. So, I expect that Timpson will charge the same or more to change the battery.

I've changed quite a few watch batteries without trouble, but you do need a set of micro screwdrivers. You can get sets of these very cheaply on Temu/ AE.

You can alos send the watch back to Casio for repair. They check it's still water resistant after working on it. Does Timpson?

I think you need a teeny screwdriver. Or maybe just a pointy knife will do. It won't be waterproof any more.

I've never had the strap last long enough to change the battery.

As pointed out, they are cheap to buy. Argos sell them for £12.99. A battery fitting shop would charge more, especially if they replace the seal.

and the review Quick delivery. Quite a decent copy of a casio but not a Casio hence the cheap price. Green light instead of white on a casio. Strap feels cheap but what did I expect for £3.99? Let's see if its accuracy is up to scratch...

Understand its a cheap item, but because the watch came with no protective packaging at all, it was pretty badly scratched when I opened it. Quality feels cheap but you get what you pay for and the stopwatch works fine which is all i'll need the watch for anyway.

At that price point, and Ebay being Ebay, it's 99.99% fake.

That looks like a lot of fun. CR2016. No wonder it runs for years and years, the battery is relatively huge.

During re-assembly of digital watches, it's possible to accidentally rotate the movement and put it back the wrong way. Using your cellphone camera, take a picture of the unit as you work.

Paul

Often the screws are machine inserted and will not budge when using jewellers screwdrivers. I have some long shaft jewellers type screwdrivers with substantial fixed handles that usually work with tight screws

Most jewellers type screwdrivers have a hole to insert a rod for leverage

If it looks at all difficult, probably way too much.

My 26 year old Rado has four tiny screws in the back and then the cover simply lifts off and the battery can be swapped. A few years ago, they wanted to send it off to be done, at a charge of over £60. I paid less than a fiver for a battery (delivered) and changed it myself. I'm not willing to pay them that much, even for a watch that costs around £2K to replace these days!

I use a mole grips on the jewelers screwdriver, and have ruined one screwdriver while doing that :-) But this is how we learn. By breaking things.

Paul

Are you referring to JIS (Japanese Industrial Standard?) ?

From the hi-res photos I can seem, Casio doesn't use JIS screws (no dot in one of the quadrants) but they are "modulo" screws, i.e. combination philips/slotted.

I have the similar Casio 593 A158W. As far as I can see they both take the CR2016 Lithium battery. I've replaced mine twice, the last time in 2016 (hey, what a coincidence!). I've got most of my batteries over the past 20-30 years from

A couple of years ago my wife bought me a small watch repair kit, watch = battery and not mechanical. It's handy though not essential, nice tool for prising the back off and the bits to take links out of a straps. I only have metal or nylon straps after getting fed up of the rubber ones deteriorating.

Of course now I end up replacing batteries for all the family but not enough to set up in business.

Ah! It fooled me. :)

So, just get the tools and change the battery.

Supposedly it should have a tiny "U" under the second "S" of "RESIST"

I have a 1980s W-51

Mine's in "scratched to f*ck" condition ...

NOT the more recent ones (it says at the end).

Mine does, but the one in the picture on the Argos website doesn't. (Presumably genuine.)