citizen eco drive

[yankeedog]

Hey all, 

             A friend of mine with a non functional citizen eco drive asked me to "take a look".So I did.To me it looks like a run of the mill quartz movement with a solar panel and a rechargeable battery.Of course it isn't listed as a battery, but rather as a "power cell" or "capacitor" which of course costs about 40 times as much as the standard watch battery it soooooo closely resembles.can anybody shed any light? pun intended.

[GregC]

I changed one of those caps a few days ago. It has a little tab that makes a connection in the body of the watch but other than that it resembles a battery.

[TexasDon]

It is indeed a capacitor, not a battery. The difference is that the capacitor can be recharged an infinite number of times where a battery, unless it's intended to be rechargeable, can't. Citizen would be a bit off the mark if they used batteries in an eco-drive. The whole idea is to present a package that is totally environmentally friendly. Seiko missed the mark with their kinetic drive watches. The original capacitors didn't have enough current flow to power the watch for an extended period. You never really see or hear Seiko referring to their kinetic line as "battery powered". Rather, they prefer to use the term energy cell. Semantics. 

The Citizen eco-drive watches are much more efficient at keeping the capacitor charged. No arm swinging required. I leave mine beneath my Dazor twin tube fluorescent light overnight and it's good for six months.

Edited April 20, 2019 by TexasDon
spelling, always spelling...

[AndyHull]

For what little it is worth, I have in my junk pile,  a no name solar watch module that has a solar panel and what I presume was a rechargeable battery (no longer in the watch module, gone long before it came in to my possession).

The only trouble is, I am not sure the solar panel is actually connected to anything, so the "rechargeable" battery may in fact have originally been an ordinary non rechargeable cell. When I get a chance, I intent to do some poking around with my multimeter to see if my hunch is correct.

 

[yankeedog]

I own an ecodrive as well, had it for over twenty years. I don't wear it all the time. I just keep it on the window sill when it is not in use. I have never had to open it. As for the cell being a capacitor, I have to wonder what type it is. having been involved with electronics at various times in my careers, I have never seen one with such a long discharge period.I remember well being told to "beware the lightning that lurks in the undischarged capacitor, lest it cause thee to bounce upon the buttocks in a most untechnician like manner". I have seen capacitors that discharge in an instant. or as in tube radios a few seconds. looking at the size of the cell, i cant imagine  that it would be more than a portion of a micro farad.  I don't see how a capacitor of that size could contain a sufficient charge in  to run a watch motor for months or even years. while a rechargeable battery could.

[GregC]

I bought a bunch of junk watches at an auction and most of them were solar, mostly Citizen and Seiko. Out of the lot, I got 2 to work after sunning them for a couple days. The rest I presume all need capacitors. I read somewhere that watch capacitors dont like being fully discharged and tend to give up the ghost. I have the rest sunbathing and they're not coming back to life.

[AndyHull]

The distinction between  capacitor and rechargeable battery technology seems to be becoming pretty grey. Strictly speaking a lot of the "capacitors" in watches are technically more akin to batteries. Supercapacitors and rechargeable cells technology is colliding.

The Panasonic watch cells in particular are described by Panasonic  as coin type rechargeable batteries, but Sieko describes them as energy storage devices. 

Other technologies exist or are being developed that produce "supercapacitors" which are more like a typical capacitor, all be it with a limited voltage range which is similar to the charged voltage of a lithium cell but with capacities in the farad or tens of farads range.

Current supercapacitors  are however typically of the order of a tenth of the energy density of a similar sized rechargeable lithium cell. The technology is developing apace, and I suspect in 5 to 10 years, watches may have their "energy storage device" integrated on to the same die as the rest of the electronics.

[TexasDon]

I'm in agreement with Andy on this one. Totally. Manufacturers are pretty good at creating new names for old products. Supposedly it helps sell them. I have a Montblanc Diplomat 149 fountain pen that according to the manufacturer is made of "precious resin". It looks and feels exactly like injected molded plastic to me. At this point the only real differences between watch capacitors and watch batteries seems to be the material used in their manufacture and the discharge rate. A true capacitor will deplete instantly when momentarily shorted to ground. A battery will suffer a partial discharge but when the short is removed, it will regain some energy. 

[yankeedog]

The difference between the two is pretty basic.in a capacitor you have two plates separated by an insulator called a dielectric.it will not allow direct current to pass and will simply store electrons until discharge..A battery or more correctly a voltaic cell is two dissimilar metals separated by an electrolyte which facilitates the flow of electrons.so a cell produces electricity while a capacitor does not.they are not totally dissimilar devices.but they are different.it seems to me that eco drive may just be a marketing ploy.where as previously mentioned something old  was rebadged into something new and a need was created where one did not exist.

[jdm]

18 hours ago, AndyHull said:

The Panasonic watch cells in particular are described by Panasonic  as coin type rechargeable batteries, but Sieko describes them as energy storage devices. 

Maybe there are inaccuracies in some marketing material but the manufacturer describes them as "rechargeable batteries", and most retailers do the same

https://www.sii.co.jp/en/me/battery/products/ms-lithium-2/

[yankeedog]

What I have been able to figure out so far is this, Information gleaned from several internet sources indicate that the eco drive power cell is actually a rechargeable lithium ion  battery. It does not like to be discharged, not fully anyway. The operating voltage is the standard 1.5 VDC, so in theory you probably could turn one into a standard quartz watch , provided you defeat the charging mechanism, because the silver oxide battery does not take kindly to recharging and you could damage or destroy your watch. So about the only thing you can do is swallow hard and pay fifty times what the battery is worth.