Accucell - Why?
 
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Thread: Accucell - Why?

  1. #1
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    Default Accucell - Why?

    Every time I see a nice Accutron on eBay and think....yeah...I'll get that one....I read the description and it says "watch serviced and regulated to run on Accucell". I don't want to pay $35/year for watch that runs on $17 batteries that only last 6 months. I thought the great voltage debate was settled long ago and we (ie experts/RKIs like Rob B) have determined that you can regulate a 214 movement to run fine on 394/380 batteries with no risk to the movement.

    Why can't the battery industry just make a battery the same size as the 394/380 that is 1.35V or a 387 size battery that is 1.35V.

    If a watch is regulated to run on an Accucell and you drop in a 394, what would happen? Does the 214 have any tolerance or self regulating ability?


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    Personally, I don’t believe you will notice much of any difference unless a slight change in accuracy that should be able to be easily regulated.

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    “Why can't the battery industry just make a battery the same size as the 394/380 that is 1.35V or a 387 size battery that is 1.35V.”

    Because there is very little demand. VIntage accutrons are the only thing that use them.

    As an example, about a decade or so ago when the renata 333, 751 and 44 were still being produced, Those batteries sell for ~$45 each, due to very low volume.


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    They don't make 1.35V watch power cells anymore because the chemistry required involves mercuric chloride, which is converted to liquid mercury in the course of the chemical reaction. This is literally the reason why those cells ceased to be manufactured. The Accucell is a substitute developed by dropping 0.2V from a 1.55V silver-oxide cell through a diode, precisely to meet the need for a 1.35V cell for those Accutrons which cannot be adequately regulated to work on 1.55V.

    Now, it's a perfectly good question why a repairer wouldn't regulate an Accutron to run on 1.55V cells, if at all possible.

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    Okay...I get it...but is the Accutron the ONLY thing ever invented in the history of all things in the universe that was designed to take a 387 size battery AND need 1.35V? It is technically possible to make a 1.35V battery in any size right? Other than the cost to manufacture it, it would be possible. The mercuric chloride was just a chemical they uses at the time. Could you make a silver oxide battery produce 1.35V?

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    Things are not that simple, for reasons of electrochemistry.

    Every set of substances which can be used in a battery has its own characteristic voltage. 1.55 volts is the characteristic voltage you get when you pair zinc metal with silver oxide : because zinc has a higher electrochemical potential than AgO, when you put the two materials in contact, with a suitable electrolyte, the silver will be reduced to its metallic state, while the zinc is oxidized, & a potential of 1.55 V is developed.

    Similarly, when you put zinc in contact with mercuric chloride, 1.35 V is developed. That potential difference is something you can't change.

    Are there other combinations of materials which will give potentials of about the same value? Sure. But they may not be practical for a watch power cell. In a real electrochemical cell of this kind, the potential developed varies somewhat from beginning to end of the reaction (ie, from a fresh to an exhausted cell). The silver-oxide & mercuric-chloride chemistries were both chosen because those two particular chemistries give an especially small variation. In other words, the cell voltage remains nearly constant until it drops off suddenly at the end of the cell life. To get that effect with another chemistry, which would be easy to manufacture into a button cell, is clearly enough of a problem that no satisfactory replacement has ever been created.
    Rob B and Mystic Nerd like this.

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    "Serviced and regulated to run on Accucell" is a little like saying "I couldn't get this to work at 1.55."

    Makes me question the veracity of the advertisement along with the quality of "service" it received.
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    Yes..... my sentiments exaclty
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    I believe Rob has addressed this previously. Maybe he will chime in again.
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    WTF Full Member Rob B's Avatar


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    Quote Originally Posted by oliverb View Post
    I believe Rob has addressed this previously. Maybe he will chime in again.
    Yes indeed he will! Rather than me type a lengthy post here about it, why not have a look at my web page on phasing accutrons, which pretty much tells all you need to know. The link is: http://members.iinet.net.au/~fotoplot/accphs.htm

    I agree with Dillworth, when someone says "Serviced and regulated to run on Accucell" , it means they don't understand what they are doing.

    Rob
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