Citizen Promaster 7817 movement battery replace

[Hughie]

I've seen nothing resembling this Eco Drive battery hold-down arrangement. Can't see any screw to slacken off to release the springy brass cover holding the battery in place. I thought that, having opened this monocoque diver's watch, removing the battery would be the easy part but life is complicated! This is my first attempt at a solar watch, completely new to this, and nothing on google has prepared me for this little shock. Photo below, full identification number is 7817-571525 TA.

(Sorry I tried to introduce myself as I'm new here but other than photo upload I couldn't get the hang of that either.)

[Galilea]

Hi Hughie, welcome. I don't have a real answer, just a guess or two, but I can hang out until those who do know come by. I'm guessing you've gently tried everything that might be obvious?  For instance, pushing where it says push, or rotating the copper part off the battery?  

Where are you, geographically? Good luck, Ill be curious to see the answer.

 

[canthus]

Looks to me that the battery has a contact pad welded to it.  Most rechargeable batteries seem to have this format.  It looks as if the battery is tucked under the mainplate at the bottom of your pic and can maybe be released by easing the top out (nearer the coil) and sliding it out upwards.  The battery is probably a re-chargeable cell that come with the contact pad as a unit.

[Hughie]

Thanks for comments, I'm in New Zealand, South Island, retired engineer with free time on hand so purchased some basic watch-mending tools and a couple of second-hand watches I liked the look of.

The replacement battery/capacitor is the standard MT920 for solar watches, according to Citizen, so that piece of brass I assume belongs to the watch and not part of the battery. I tried gently pushing the brass plate sideways, then upwards, maybe it just needs a little more force.

[Hughie]

On closer inspection:

1. the brass plate is indeed firmly attached to whatever battery is installed here - where could anyone obtain such a battery/plate combo nowadays?

2. I thought maybe undoing the screw located close to battery (below right of battery in photo) might release things but that circular plate is attached at two other points (at least) so nothing moves and no other screws to remove ('clips' seen at 11 o'clock and 2.30 in photo) - what to try next?

[JohnR725]

On 8/24/2023 at 4:23 AM, Galilea said:

pushing where it says push

uusually on watches  that say push  that's to give you a clue where to push to get the stem out.

On 8/24/2023 at 3:58 PM, Hughie said:

The replacement battery/capacitor is the standard MT920 for solar watches, according to Citizen,

is that actually went citizen says?  Usually if you look at the rechargeable batteries that is one of the common batteries  then the watch companies usually weld on various things to hold it in place so you do need to get the specific battery for your watch as opposed to a generic battery because it's not going to have the bits and pieces welded on exactly right.

yyes I remember when I go to work tomorrow I'll ask if anyone has experience with this. They change a lot of these things so maybe they've seen this one before  I typically don't do these things.

 

 

[canthus]

Looking at the service sheet for 7817 movement the battery part for the 78** series is 298-177 GC970.  Cousins UK list it but as being discontinued.  You could try searching for suitable replacement.

[JohnR725]

42 minutes ago, canthus said:

service sheet for 7817

technical sheet is attached always nice to attach one when talking about it

43 minutes ago, canthus said:

298-177 GC970

then if you Google the part number well the first link I found was this one so it does look like it's available just probably not from citizen

https://www.smallbattery.company.org.uk/sbc_298-177.htm

then for how to get the battery out that's with the technical guides for it looks like you have to remove the plate.

 

 

 

 

1023_Citizen 7810, 7820, 7860, 7870.pdf

[Hughie]

All this chat is incredibly helpful, thankyou so much to all.

I'll try to remove the top plate once more, diagram showing that single screw should release the plate (it doesn't, not for me anyway, but I guess a little bit of persuasion may be required as it's likely been there for several decades). Anyway, I'll read the instructions carefully and post any more details of final outcome.

[Galilea]

3 hours ago, Hughie said:

All this chat is incredibly helpful, thankyou so much to all.

I'll try to remove the top plate once more, diagram showing that single screw should release the plate (it doesn't, not for me anyway, but I guess a little bit of persuasion may be required as it's likely been there for several decades). Anyway, I'll read the instructions carefully and post any more details of final outcome.

Holy heck, I have learned never to buy one of those, lol. 

.

 

[Hughie]

To complete this sorry story:

1. The top plate remains firmly attached after removing the single screw. The tiny gap only allows a thin knife to slide under the plate until those other 'clips' are reached and I cannot separate them. But removing the screw allows just enough flexing for the battery to be prised out from underneath it - doesn't seem to be the intended method but best I could do.

2. The battery specified in the Technical Information sheet seems no longer available but it is based on a gc920 (also untraceable in my searches) for 781* movements or MT920 for 782* series. So I've ordered a bare MT920 (unmodified) that I hope will have enough electrical contact without that unusual brass plate added to the +ve side. If not I can likely affix a small strip of brass to help hold it in place and improve contact, fingers crossed.

3. Finally (the fun part) I tried removing the unusual brass plate from the old battery (so I could add it to the new one when it arrives and so I could check the writing on the +ve face). Soldering iron was my weapon of choice. Y'all likely know that a soldering iron won't free these welded-on additions but it is hot enough to cause the little cell to explode violently after a minute or so of heating. Not recommended unless you have a death wish...

[JohnR725]

34 minutes ago, Hughie said:

The top plate remains firmly attached after removing the single screw.

usually with watches like this and it's hard to see in the picture plus it doesn't indicate that there are usually these little tabs that go down and latch on to the plastic or whatever is below it. As they have to go around to look at all the little things that look like tabs that are holding it in place because just as the image shows it can come off you just have to release the things that you can't see.

I've run into watches were there is no screws at all it's just the little tabs. This is where it be really nice to get a detailed picture of the upper plate where we can see that.

36 minutes ago, Hughie said:

unusual brass plate from the old battery

oh the usual plate as the battery in this watch ever been changed?

okay I swiped her image and circled three items what are those items would they be the thing to release the plate?

okay greatly expanding the drawing which really sucks notice the three let's call them latches they latch the plate into place they have to be popped out otherwise it's never coming off

one of the problems with technical bulletins is it assumes that whoever's reading it actually as a clue of what they're doing and it's only there to provide helpful information. It's not there is a step by step guide of exactly how to do procedural things like  releasing the upper plates.

now for the battery question something peculiar

notice we don't see anything that's attached to it?

Then yes typically all of the rechargeable capacitors or now days a rechargeable lithium batteries typically always have something welded on and in your case there is nothing or at least nothing in the image

but in your image looks like there is something conflicting with the service guide

this is why asked if somebody had changed it?

48 minutes ago, Hughie said:

So I've ordered a bare MT920 (unmodified) that I hope will have enough electrical contact without that unusual brass plate added to the +ve side. If not I can likely affix a small strip of brass to help hold it in place and improve contact, fingers crossed.

so back to my battery confusion technical drawing shows nothing added to the battery your picture shows definitely something added to the battery and the link to the website that has the battery claims that is just a  battery so looks like you don't have to have anything added on.

Sometimes what happens and that's why I asked if somebody changed it they didn't have the right battery and they shoved something in and then worst-case especially for this watch what if they didn't know how to take the plate off maybe they modified where the battery goes and now you're stuck with the crap they put in. Because it does look like a standard whatever these are rechargeable should go in with no other thing is added at least based on the drawing and based on the site from the battery company unless somebody got creative and modified yours

 

 

 

[Hughie]

The amount of detail from JohnR is very helpful, and thoroughly interesting.

Those three tabs circled in your diagrams above are certainly the things holding the top plate firmly in place; wedging my thin knife blade under the top plate, I couldn't force them to pop off so there is more skill needed there than I possess. The good thing is the battery can be prised out (and probably forced back in) with only minimal permanent distortion, which replacing the screw should easily rectify (fingers crossed). I think I might cause permanent damage by clumsily attempting to pop those latches.

I purchased this watch (plus one other) only a month ago (a week of exposure to bright sunlight still failed to energise it enough to run through the night without stopping) so I only surmised this could be the original battery. The instructions seem to differentiate between a 'capacitor' for the 781* and a 'secondary battery' for 782* series and my searches lead me to the (obsolete) 298-177-gc970 cell for this particular watch, so I thought maybe that "..gc970" extension denoted the version with the unusual brass plate added but can find no more info on this obsolete cell (other than that all the 298-177's are superseded by 295-57, and your photo above kinda confirms the bare Panasonic MT920 is correct either way). There are no visible modifications to the battery space so we'll see if the MT920 will work or if it needs some added brass connector. Again, fingers crossed. (My camera has let me down, otherwise I would post a photo of the empty battery space but it looks to be unmodified, nothing obviously messed up anyway.)

[Hughie]

...and a photo of the battery space of the Citizen 7817 with 'exploded' battery alongside (don't try that at home!) - I wonder if one of those two 'contact springs for solar cell' shown in the first diagram posted by JohnR might be the brass plate affixed to the +ve side of the battery?

...and for the first time we can see from the photo above that the movement is actually 7867A, not 7817 as stated on the watch case. From the specifications on page 3 of Tech Info, battery used is 298-226 and not 298-177, "capacitor block with lead plate" - back to google searching  so sorry for misleading everyone.

[JohnR725]

1 hour ago, Hughie said:

actually 7867A

okay that makes sense because now finding a picture of the battery it matches what looks like you're supposed to have.

https://www.stsupply.com/citizen-capacitor-298-226-gc920.html

what I'll try to remember to do tomorrow is ask the people in the front room to change the batteries how to release yours. As looking online I'm not seeing anything at all which I'm finding quite interesting. Well not exactly I did find something that looked promising except it was this discussion. I always do find it interesting when I find the discussion that I'm currently trying to get an answer to.

 

 

[Hughie]

Final update: after several failed attempts (and refunds eventually received) I've been unable to source a replacement 298-226 capacitor. Most suppliers list it as discontinued/unavailable. I even attempted to attach the brass plate from the old capacitor to a new MT920 using conductive glue but that hasn't worked. Other than replacing the entire mechanism, I seem to have a collection of scrap metal. Okay, thank you everyone for advice.