# Eco Drive Capacitors



## Griff

I've read someone say that Kinetics have a capacitor life of about 5 years.

I'm sure that is way out.

Here is some info on Citizen Eco Drive capacitors:-

Citizen Eco-Drive Movements and Batteries

Created 01-18-2002

Updated 05-14-2002

This page attempts to explain the construction and power source of popular Eco-Drive movements from the Citizen Watch Company.

All of the findings and comments here are the results of my observations as an owner of six various models of these watches and do not necessarily represent the opinions of the Citizen Watch Company.

For more exact information contact: Citizen U.S.A.

Popular lore suggests that the Eco-Drive series of watches will run by solar power alone and "will never need a battery".

Our observations show that these watches contain a rechargeable battery to keep the watch running when there is no light falling on the solar cell. A simplified schematic operational diagram may be found on our movements page.

Primary Power Source

In the Eco-Drive design the primary power source is a solar cell located behind the translucent face of the watch. This can be seen in certain models at certain viewing angles as a cross with the intersection at the center of the watch face.

The solar cell creates electricity whenever light strikes it. Unfortunately, the amount of current which such a small solar cell produces is not enough to power the functions of a watch.

To provide the power to run the watch a rechargeable battery is installed, and the solar cell recharges the battery. Since the battery, when installed already has a charge the solar cell is able to keep up with the power demand of the watch movement.

When the rechargeable battery is fully discharged the watch stops functioning until the solar cell has charged the battery enough to run the watch.

Battery

The choice of a Panasonic Manganese Titanium Lithium rechargeable battery to power these watches is a good one since this type of battery was designed specially for this type of service. This type of battery has a capacity of more than 10 times that of capacitors of the same size.

Full specifications for this line of batteries can be downloaded HERE (Note: this is an Adobe Acrobat .PDF file).

The MT920 battery can operate for 2500 hours at a 1.2uA load with a flat operating voltage of between 1.5 and 1.2 volts.

Charging efficiency is nearly 100% with very small charging loss.

The MT920 can withstand temperatures as high as 60 Deg. C (140 Deg. F) and charge voltages as high as 2.6 volts.

The life of the battery is as much as 500 full discharge cycles to a discharge low limit of 1.0 volt. A discharge depth of 100% is possible.

*Battery Life*

The replacement life of these batteries is hard to determine because of the many factors involved. Most of our computations suggest that, in an ideal operating environment, a battery should need replacement somewhere between 15 and 28 years.

A simplistic example:

A Citizen Skyhawk can run for 4 years on a fully charged battery.

The battery may be fully charged/discharged up to 500 times.

A simplistic calculation may imply that (4 Years per charge * 500 maximum charges) = 2000 year battery life !

This, of course is wrong, because it does not take into account aging of the components of the watch, battery electrolyte, temperature and voltage aberrations and other factors.

This demonstrates why it is so difficult to determine the replacement life of one of these batteries.


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## MarkF

Nice post Griff, thank you for that.









I still have reservations about my new Eco however they are reservations about the photocell not the battery.


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## Nalu

I think that Kinetic/4 year thing applied to the initial generation of Seiko Kinetics. The 2G Seiko Kinetics (which appeared fairly soon) remedied the problem, IIRC. Never say any estimates of how long an Eco-Drive might last, thanks for the post! For the record, the only problem I ever had with an Eco-Drive was with a Promaster Tough, which refused to fully charge right out of the box...


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## Boxbrownie

Has anyone here ever had to have an Eco-Drive watch battery replaced at all?

Would be interesting to know if only to quosh or re-inforce people percieved fears of these high tech beauties fiobles! Obviously the info will only be useful if we know why the battery was replaced ie fault in manufacture/damage or end of life?

Best regards David


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## jcalka

Before I purchased my Casio Frogman, I remember finding a story or two about a leaking battery or capacitor, and one issue about heat warping an Eco-zilla dial. I think these stories were few and far between, and maybe the jury is still out on the "real" life expectancy.

I only have two quartz watches and I think the rule of thumb is that any quartz movement will not be serviceable past 20 years due to obsolescence. I'm not planning on handing my quartz down to my sons, but I do like the technology at the present.


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