Vintage watch battery compatibility chart

[xevious]

Is there a chart available somewhere that lists older watch battery models and their equivalent modern day replacements? I do know that some battery model numbers change over time, especially as one maker phases out a battery and another takes over. And sometimes a battery maker will retire a particular number and start using another. I'm hoping that information is captured somewhere.

Of course, I'm very interested in finding out about a modern day replacement battery for the one in my vintage watch. Unfortunately, there seems to be very little information about it on the Internet. I'm looking for a button cell equivalent to models 726R or 920R... not silver oxide, but some kind of lithium blend that is rechargeable. Any ideas? Thanks!

[rewolf]

Hello xevious,

(also answering this thread)

links to some battery comparison charts:
Button cell comparison chart
Another one
3rd one...
However all not useful for your specifc request.
Varta has a comparison chart online: http://trade-info.varta.com/salesmaterial/files/00593_VD_UZ_Bestueck14.pdf
A bit outdated (2001), but it mentions the "726R + S.T." for a Casio "QW-189" and "920R + S.T." for "QW - 242".
Dunno what S.T. means.

What's the size of the battery you need?
SR726W/SR59 has D=7.9mm, H=2.6mm
SR920W/SR69 has D=9.5mm, H=2.1mm
Do you know the voltage required? There are different chemistries.

Could this be what you're looking for? SII MS920S http://shopping.microbattery.com/s.nl/it.A/id.6796/.f
Rechargeables by Seiko Instruments: http://speed.sii.co.jp/pub/compo/battery/productBatEN.jsp
Good comparision of different chemistries.
SII micro battery catalogue
2006 catalogue
2002/3 catalogue
2001/2 catalogue

Panasonic MT920: http://www.panasonic.com/industrial/battery/oem/chem/lith/mangtit.htm
Panasonic Lithium Batteries, various chemistries, including rechargeables:
http://www.panasonic.com/industrial/battery/oem/chem/lith/index.html

MT920/TS920 also available here: http://www.abcde.de/mt920s.htm (30km from my home)
http://www.abcde.de/lithium_knopfzellen_aufladbar.html


Maybe XR9527W: D=9.5mm, H=2.6mm
http://www.watchbattery.co.uk/shop/products/BW-952.shtml
http://www.smallbattery.company.org.uk/sbc_xr9527w.htm


I suppose you already know casionerd's data sheet?

[xevious]

Rewolf, Danke schön! Thank you VERY much for the links you have provided. You certainly know where to look for watch batteries across the Internet.

I did see CasioNerd's data sheet--that's how I figured out one of the battery models used. I didn't think to take measurements of the 920R battery I have--I'll have to do that as well as closely examine the watch for any other markings.

Although the manual recommends 726R, my watch currently has a 920R installed (exhausted). And you pointed out SII brand MS920S Lithium Rechargeable Battery, 3.1V 11mAh. "920" is in common, which is promising. But... I have no idea what the voltage or milliamp rating is for the 920R. The 370 and 371 suggested are rated at 1.55V and 45mAh. If that is compatible with my watch, then I'm not sure if the MS920S will work. But you did link me to ABCDE (clever domain, abcde.de), and the MT920 is 1.5V, which could be it.

You're right--the Varta chart does show "920R S.T." matching module QW242. Does that mean Varta does have a battery for it, or is this just a historical reference?

[rewolf]

Rewolf, Danke schön! Thank you VERY much for the links you have provided. You certainly know where to look for watch batteries across the Internet.

I have gathered quite a collection of battery data sheets and links

Basically, there are 2 types of batteries that could fit your watch:
a) high voltage range (3.0V to 2.0V, similar to Lithium coin cells), SII MS920S or Panasonic ML920
b) low voltage range (1.5V to 1.0V, similar to Alkaline coin cells), Panasonic MT920

To determine the correct battery, you can try the following:

1) Test if the watch runs with with a cheap 1.5V AG6 Alkaline cell (same size as SR920). Don't let light fall on the solar cells to prevent them from delivering voltage to the battery (would adulterate the measurement).
If you have a laboratory power supply, try with voltages from 1.5V down to 1.0V (add 1kOhm series resistor to prevent damage in case you short-circuit something by accident).

2) To find out the maximum charging voltage, take out the battery, expose the watch to full sunlight (or strong halogen lamp, but flourescent won't work). Then measure the voltage on the battery connections.

3) Measure the size of the battery compartment.

4) Tell exactly what's written on the currently inserted battery (brand etc).


Rechargeable battery summary (click here for chemistry comparison by Panasonic):

High voltage range:

Panasonic VL (Vanadium Pentoxide)
Charging voltage min 3.25V, max 3.55V
Average voltage 2.85V (3.0V to 2.5V)
VL621 (D=6.8mm, H=2.1mm): 1.5mAh discharged to 2.5V
Correct charging is quite critical, IMO not well suited for solar watches.

Seiko MS (Lithium Manganese Silicon)
Continued stable capacity characteristics even after the battery is overdischarged down to 0.0V.
Charging voltage min 2.8V, max 3.3V
Nominal voltage 2.5V (3.0V to 2.0V)
MS920SE (D=9.5mm, H=2.1mm): 11mAh between 3.1 and 2.0V

Panasonic ML (Manganese Lithium Aluminium)
Charge voltage 2.8V to 3.2V
Average voltage 2.5V (3.0V to 2.0V)
ML920 (D=9.5mm, H=2.1mm): 11mAh discharged to 2.0V

Low voltage range:

Seiko TS (Titanium Silicon Lithium)
Low-voltage chargeable, 1.5V to 3.0V
Average voltage 1.3V (2.0V to 1.0V)
TS621FE (D=6.8mm, H=2.1mm): 4.2mAh between 2.3V and 1.0V

Panasonic MT (Manganese Titanium Lithium)
Excellent voltage and overdischarge withstanding characteristics
500 full discharge cycles (down to 1.0V)
Charging Voltage 1.6V To 2.6V
Average voltage 1.2V (1.5V to 1.0V), very similar to Alkaline
MT920 (D=9.5mm, H=2.1mm): 4.0mAh discharged to 1.0V

Panasonic NBL (Niobium Lithium)
Excellent at withstanding overdischarge and overcharge
Charging Voltage 1.6V To 2.6V
Average voltage 1.3V (2.0V to 1.0V)
NBL621 (D=6.8mm, H=2.1mm): 4.5mAh discharged to 1.0V

[xevious]

Wow... rewolf, you sure went to a lot of trouble for me. I greatly appreciate it!

The 920R battery I have is branded with Yuasa, Japan, and measures 9.5mm x 2mm. I don't know what the voltage or milliamp is. But given the recharging aspect, I'm starting to believe that the watch has a low power requirement from the secondary cell. There is a back light switch, though...

I double-checked my manual... nothing said about the voltage specifications of the watch. If only there was some detail on the 726R or 920R battery somewhere... then it would be very easy.

But I think you've got the right idea... try out a low voltage silver oxide battery with the solar cells covered. If it works, then that's the battery to use. Probably the best bet is to buy both batteries at once from an on-line retailer, as some of them aren't all that expensive (I've seen some listed as cheap as $2 per battery). I'll look into it and let you know what turns up.

From what you've listed, the 9.5mm sized ones are the candidates: Panasonic ML920, Seiko MS920SE, and Panasonic MT920. It would be great if I could buy all of them from the same website... I'll have to look around a bit.

If this works out, I'll have to see about getting one of those vintage solar watch websites to add the details, in case someone else starts looking into this.

[rewolf]

Wow... rewolf, you sure went to a lot of trouble for me. I greatly appreciate it!

No trouble, pure fun Nerd fun, to be exact...

The 920R battery I have is branded with Yuasa, Japan, and measures 9.5mm x 2mm. I don't know what the voltage or milliamp is. But given the recharging aspect, I'm starting to believe that the watch has a low power requirement from the secondary cell. There is a back light switch, though...

Backlight, oops. Lots of current. Yuasa is funny - I didn't even know they make microbatteries, only know their vehicle batteries.

But I think you've got the right idea... try out a low voltage silver oxide battery with the solar cells covered. If it works, then that's the battery to use. Probably the best bet is to buy both batteries at once from an on-line retailer, as some of them aren't all that expensive (I've seen some listed as cheap as $2 per battery). I'll look into it and let you know what turns up.

Better use alkaline instead silver oxide for testing. The latter has constantly 1.5V until totally discharged. Insert alkaline AG6, press backlight switch, see what happens - and you can get 10 AG2 for $2

If this works out, I'll have to see about getting one of those vintage solar watch websites to add the details, in case someone else starts looking into this.

Yeah, spread the knowledge, always my mantra. Who does not know must believe everything

[xevious]

I also enjoy the nerd factor. I can't wait to sport my old Casio LCD, proclaiming "Nerd having fun here".

Yeah, Yuasa must have dabbled in the watch battery business for a short while. There is practically no information about it on-line.

OK... the 726R and 920R appear to be 1.5V batteries. They both match up to the 371 and 370 cells. I'm thinking it may be OK to use a low drain one (371), not reacting to the trickle charge from the solar battery.

The MS920S (Seiko) is a 3V rechargeable battery, while the MT920 (Panasonic) is 1.5V rechargeable. I don't understand why there is such a price difference, with the MT920 being 10x the cost of the MS920S. Is it indeed a "capacitor" having a more sophisticated design than a lithium battery? MT = Manganese Titanium? Citizen does boast that the secondary battery is ecologically friendly--no toxic materials, so no lithium.

[rewolf]

OK.. the 726R and 920R appear to be 1.5V batteries. They both match up to the 371 and 370 cells. I'm thinking it may be OK to use a low drain one (371), not reacting to the trickle charge from the solar battery.

You can try this, but I don't know how the AgO battery reacts to being trickle charged by the solar cell. In the worst case it could leak, in the best case it will last forever...

The MS920S (Seiko) is a 3V rechargeable battery, while the MT920 (Panasonic) is 1.5V rechargeable. I don't understand why there is such a price difference, with the MT920 being 10x the cost of the MS920S. Is it indeed a "capacitor" having a more sophisticated design than a lithium battery? MT = Manganese Titanium? Citizen does boast that the secondary battery is ecologically friendly--no toxic materials, so no lithium.

MT is definitely not a capacitor, it would have a totally different charge and discharge curve. Panasonic writes it is "Manganese Titanium Lithium" (see link given above) - I don't know how toxic that is, certainly I wouldn't eat it

[xevious]

MT is definitely not a capacitor, it would have a totally different charge and discharge curve. Panasonic writes it is "Manganese Titanium Lithium" (see link given above) - I don't know how toxic that is, certainly I wouldn't eat it

That's interesting... so those websites citing the MT920 as a capacitor are full of it then? Or maybe at some point the MT920 was made as a capacitor, then Panasonic switched to providing a lithium based battery instead?

Yeah, I wouldn't eat one either--just thinking of the environment.

[rewolf]

That's interesting... so those websites citing the MT920 as a capacitor are full of it then? Or maybe at some point the MT920 was made as a capacitor, then Panasonic switched to providing a lithium based battery instead?

I'd rather believe the Panasonic MT920 datasheet, and it says battery, not capacitor. It has the charge and discharge voltage characteristic of a battery, not a capacitor.
BTW: A capacitor delivering 4mAh (=14.4 Coulomb) when discharged from 1.5V to 1.0V (like the MT920) would have a capacity of 28.8 Farad! Even with the best currently available technology it'd be bigger than the whole watch. But you could charge and discharge it within seconds for many hundred thousand times

[xevious]

In the battery compatibility spreadsheet I downloaded, the AG6 maps to the 371 and is showing on a vendor website as having a chemistry of "Zinc / Monovalent Silver Oxide". I haven't been able to locate a US based vendor selling an Alkaline equivalent... they seem to be all silver oxide based (Renata, Energizer). I've tried searching on other key terms, like SR69, but still didn't turn up Alkaline. It would be great if I could buy all of the batteries from one source... oh well.

I did hear back from a Casio collector, who has dozens of vintage Casio watches that he wears frequently. He says he has successfully used 3V button cell batteries in Casio watches known to take 1.5V as recommended by Casio. But he doesn't have any solar watches... so, like you mentioned earlier, my DW-2000 might not be capable of recharging the 3V cell and it will end up requiring a battery replacement earlier than expected. The MS920S is cheap to buy for me ($1.50), so I might as well give it a shot. The good thing is that I've got a "junker" Casio solar watch that has a badly damaged case, but functional module. I can test replacement batteries in it first, just to see if they work or cause damage, before using in the DW-2000.

I'll post my results later on.

[Oldcasiofan]

Just came across this board and this message searching for the elusive Yuasa 920R. My own search started in the early 1990's in the early days of the internet and no google so it was hard to find battery information. I have an old Casio DW-2000 with the solar cells and let me say that when the manual says battery life is 7 years, it is 7 years. So after the first battery died and I could not find the Yuasa locally I contacted Casio in Japan, they referred me to Casio USA and they sent me a list of battery stores that "carried" the 920R. Contacted a few and ordred what I thought was the 920R only to recieve a 920W or SW920, something like that. Of course none of them worked, but then I came across one company that knew what I was talking about and was told that the 920R is a rechargeable lithium battery and as best as I can recall was 1.5volts. When I asked about the Silver oxide button sells, he had heard it all before and for whatever reason they just do not work. I have tried all silver oxide 920's and the conversion numbers as well none work. Please let us all know if the MS920S works.

[rewolf]

Welcome Oldcasiofan,
The answer to your question is in this thread.
In short: it didi not work for xevious, but maybe his movement is just defect. MS920S will quite probably not work, it won't take any charge at 1.5V.
Did you ever try Alkaline button cells instead of Silver Oxide? See also the other thread for more information about this.

[xevious]

Well, I finally tracked down someone who has a working Casio vintage solar watch with a 242 module (same for the DW-2000). The battery they have installed is the SR-920W, a 1.55v cell. The Panasonic MT920 is supposed to be equivalent.

The Renata 371 is an SR-920W, which I did buy and install in mine. So, my module must be dead.

Note that the SR-920W is not rechargeable, so the solar function is not being used. This means battery life may be about 3-5 years.


EDIT:
I was able to get a working module from a bashed up example. It came with a Sony SR920SW battery in it. It is not a rechargeable cell, but from what I understand the trickle charge from the solar cells isn't enough to bother it. Just not a good idea to expose the watch to a lot of sunlight. Lastly, you can do a simple thing to disable it. Cut a small piece of tape and apply it over one of the module contacts for the solar cell.