Electric Clock Maintenance and Repair, Part 2

Welcome to the second installment in a series on maintaining electric clock(s). This post will deal specifically with battery-powered quartz clock movements, as they are the most commonly encountered in consumer-oriented clocks. I'll discuss prevention of damage herein, but the following post will deal with how we can repair any damage our clocks suffer.

MOVEMENT ASSEMBLY

As you see in the illustration below, the whole assembly includes the movement (possibly a hanger), dial, washer, retaining nut, hour and minute hands, and second hand or possibly a cap nut at the end.

Typical square quartz clock and related parts

CLOCK MOVEMENT SHAFTS

You might think that the clock world is standardized but that's not quite true. It's typical that the motors are about the same size, but from there everything can vary. For example, here are the various shaft lengths that I found today as I surveyed the options:

"Standard" threaded shaft sizes

Shaft diameter is more standardized and is usually 8mm (5/16").

MOVEMENT VARIATIONS & COMPLICATIONS

If the movement in your clock has been ruined by a leaky battery or has just expired from old age, you may find it very difficult to locate the correct replacement movement. Here are some of the variations in a "generic black box quartz movement":

Regular jumping seconds
Regular smooth seconds

High Torque (long hands)
Weather resistant / outdoor

Time and Tides
Time and Thermometer
Time and Timer

Time and Day of the Week
Time and Date of the Month

Time auto adjust by "chip"
Time auto adjust by radio/"atomic" signal
Time auto adjust by satellite signal (not yet outside Japan)
Second time zone

Reverse Time (Barbershop)

Pendulum
Dual Pendulum

Motor case round
Motor case miniature
Motor case clips in place

Button Cell power
AA Cell power
C Cell power
AC power

Chime with speaker
Chime ext speaker
Chime 6 melodies
Chime 4 melodies ext speaker
Chime recorder/mic/playback
Chime Cuckoo clock

There are 10 "generic" quartz movements in this set of Seiko clocks. With the exception of the 2 press-in movements in the dual desk clock, the movements are all different from one another!

Assortment of Seiko quartz clocks

PRESS-IN CLOCK MOVEMENTS

The desk clock uses another form of "generic" quartz clock. The "press-in clock insert" is normally round, with a standard diameter of 36.5mm (1 7/16") and depth of about 9.5mm (3/8"). Notice the receptacle which is optional - you can push the movement right into a hole bored in wood or other backing material.

Press-in clock movements

OTHER MOVEMENT VARIATIONS

Some of my thin clocks use a tiny movement powered by a watch battery.

Ultra-thin movement with button cell power

Some clock motors are assembled specifically to power complication modules. This is a bit like tacking a Dubois-Depraz chronograph module onto a watch's ETA "motor".

In this case the quartz clock motor has to have some gears added to the front shaft, to drive the module. For example, my calendar moon phase clock has what looks like a normal quartz movement:

Calendar moon phase clock motor (and corroded area where battery leaked)

However, when the motor is removed from the module, we can see the gears which need to be powered in addition to the hands which are affixed normally.

Calendar module drive gears

Several of my other Seikos have complications that are powered the same way. One of those motors failed, and I had to refit its shaft gear into a newer motor (a total pain) because Seiko considered 20+ years an unreasonable time to stock this specialty part. And I can't blame them.

So let's not let these clocks get ruined by a leaky battery! I'll get back to the battery subject now.

BATTERY POWER

Batteries are small chemical factories which work "around the clock" producing electricity to power small devices. About 3 billion disposable batteries are sold each year in the US. They come in dozens of configurations, but for powering wall clocks, the most commonly used batteries are AA and C cells.

I suspect that most households keep a battery inventory. My parents used to keep theirs in the refrigerator, but I can't waste that space on batteries. Here's my cigar-box full:

Alkaline disposable AA, 9V, C and D Cells

Batteries contain small amounts of toxic materials, so they should be disposed of at a recycling facility. Strangely, the closest places near my house are Barnes & Noble bookstore and Home Depot.

Bad batteries waiting for disposal

The best way to know if your batteries are good or bad is to use a battery tester. Tiny testers with an analog dial that you got at Radio Shack years ago probably aren't adequate anymore. If you have one, toss it and buy a new one that can test each type of battery sold today.

I think this is the best one readily available - it cost me about $75 and after going through a large box of discarded batteries at my office, we were able to reclaim about $100 worth of batteries.

High-quality battery tester

I throw away anything under 40% and replace it with a new battery. It's not uncommon to have one battery at 20% and a second in the same device at 80%. If you need to replace one of a pair, put two new ones in the dual-battery device and put the old one you want to continue using into a unit by itself.

Watch and regular battery testers

ALKALINE BATTERIES

Alkaline batteries have greater output than standard (zinc-chloride) cells because the manganese dioxide chemistry is more efficient (in some ways). An alkaline cell provides three to five times the capacity of a standard battery. However, alkaline battery capacity is related to its load. An AA-sized alkaline battery can have a 3000 mAh capacity at low drain (clock movements), but as little as 700 mAh with a heavy load of 1A (digital cameras). The alkaline cell delivers full capacity on intermittent or continuous light loads. These are all good things for clock fans.

The bad news about alkalines is the noxious byproducts they emit. As alkaline batteries discharge, their chemistry changes and hydrogen gas is generated. This gas increases the pressure in this tiny "voltage factory." Eventually, the pressure either forces its way through insulating seals at the end of the battery, or its seams. Once a leak has formed and the shell begins to corrode, potassium hydroxide escapes and combines with carbon dioxide, forming a potassium carbonate feathery crystalline monster which spreads out along metal electrodes, wires and circuit boards. The crystalline growth can spread from the battery, coating it with fur, and corroding anything it contacts. It causes permanent damage to metal, wood and other clock components.

LITHIUM BATTERIES

Lithium batteries use a completely different chemistry, can be dangerous because they get hot, are expensive and have other issues that make them marginal, in my opinion, for our clocks. So far I have only tried a couple sets, and I found they didn't last very long - less than a year for my digital "atomic" clock.

Battery leak damage

RECHARGEABLE NIMH BATTERIES

Most rechargable batteries today use Nickel-Metal Hydride chemistry. NiMH cells have a faster self-discharge rate than Nickel-Cadmium cells (which are more hazardous and now less common). The self-discharge rate varies greatly with temperature; lower storage temperature is better. This makes them unsuitable for many light-duty uses, such as clocks or smoke alarms, where the battery is expected to last months or years.

A low self-discharge nickel–metal hydride battery (LSD NiMH) was introduced a decade ago by Sanyo. By using different electrode separators and improved positive electrodes, they can retain about 70% to 85% of their capacity for a year at 20 °C (68 °F). Since wall clocks are normally "up on the wall", they operate in higher temperature air than we realize - thus losing power more rapidly. NiMH cells only produce 1.2V compared to 1.5V for alkaline cells, so our clock movements are starved for power, sooner.

RECHARGEABLE BATTERY FEATURES TO LOOK FOR

It is more ecologically friendly to use recyclable batteries, but it's a pain to keep them on hand, charged, and change them more frequently than alkaline. We need a battery that retains a charge for a long time and can power a low, steady drain for a year or two. You don't want a battery optimized for short, high-drain applications like a cordless drill or camera flash unit. We won't want it to leak or burst into flame.

I can't recommend any specific brands, as I know fairly little about this subject. I just look for the largest capacity, which is indicated on the battery itself, and adequate voltage. Also check to see that they are low-self-discharge type (mine are not).

Capacity is indicated on the side, often in small print

If you use rechargable batteries you also will need a charger designed for the type of battery you choose. This is a massive subject in itself. If you go onto Amazon and research the subject, it appears that every third adult male in North America is secretly a battery chemistry engineer, and spends his evenings poring over a bank of digital volt-ammeters in his garage, checking out the quality of every brand of battery and charger. I am NOT one of those guys, although over 40 years, I've accumulated a few chargers.

Assorted battery chargers

I now use this "intelligent" La Crosse charger because it came with lots of high-capacity batteries and some adaptors. It works pretty well, but only charges AAA and AA cells. We have 2 because my wife is a PE teacher and her megaphone ("You kids, get away from that cliff!") needs 8 batteries at a time. And she drains them every week; just the opposite of a Purist's clock. The charger has nifty displays and can even let you know there's time for another glass of Pinot Noir before the batteries will be ready.

High-tech battery chargers

I use my older chargers to charge the occasional C cell, and of course every digital camera pretty much demands its own piece of equipment. I have 3 Sony camera chargers. Two are no longer necessary, but I still have them around. I might as well throw them in the recycling box with all the bad batteries. Because battery chemistry has changed dramatically in the last 20 years, older chargers are not really appropriate.

SUMMARY

We've looked at the variety of clock motors and hinted at the obvious virtue in NOT letting batteries mess up the one that came in our favorite clocks.

I've described why alkaline batteries are good for powering clocks, and why they can ruin them. I didn't say it outright, but I feel NiMH rechargeables are safe, ecologically-sound, reasonably priced, yet marginal for powering clocks. I'm now conducting tests ...

At this point, we have enough background on clock movements and batteries. In the next part of this series we will take a few clocks apart and see if we can mitigate the damage from leaking alkaline batteries.

Thanks for patiently reading!

Cazalea

Clock on the bench

This message has been edited by cazalea on 2015-06-11 13:56:45 This message has been edited by cazalea on 2015-06-11 16:26:17 This message has been edited by cazalea on 2015-06-11 17:04:45

Horological Meandering

Electric Clock Maintenance and Repair, Part 2

Electric Clock Maintenance and Repair, Part 1

Electric Clock Maintenance and Repair, Part 2

Electric Clock Maintenance and Repair, Part 3