Battery Replacement

What is the correct battery for my Accutron?

214batt.jpg - 15.69 K Bulova Accutron watches were originally designed to use Mercury batteries of 1.35 volts, since they were the only type manufactured then. The pic (left) shows an original 214 all-metal "top hat" cell, before 387 cells with the plastic spacer became available. In most areas of the world, mercury-based batteries are no longer available, due to environmental concerns related to the safe disposal of them.

The Tuning Fork watches manufactured by Esa (e.g the f300 Omega) were designed to run on either mercury or silver oxide batteries without any adjustment, provided the last repairer to work on the watch set up the index mechanism according to factory specifications.

It is strongly recommended that you do not replace batteries yourself, as special tools are required to open the watch case without damaging it. The only exception to this is the Accutron 214 model, which has a small battery hatch on the back.

DO NOT use batteries based on any other cell chemistry than silver oxide or mercury, or severe damage to your watch may occur due to leaking chemicals or gas, which have nowhere to dissipate in a sealed watch except onto all the working parts. This applies especially to Zinc-Air cells, which at first glance may appear to be a good alternative to mercury batteries. To find out more about watch battery construction and chemistry, click here.

Battery Selection Table
Model Mercury type Silver Oxide type
214 387 387S, 394**, SR936SW** Accucell 1
218 343 344, 350. SR1136SW Accucell 1
219 343 344, 350, SR1136SW Accucell 1
2210 388 329, SR731SW*** Accucell 2
230 343 344, 350. SR1136SW Accucell 1
224 343 344, SR1136SW Accucell 1
ESA 9162/4 343 344, 350, SR1136SW
ESA 9210 343 344, 350, SR1136SW
Omega 1220 343 344, SR1136SW
Omega 1300 313 357, SR44
Omega 1301, 1302 343 344, 350, SR1136SW

***Not a perfect fit, but there is no direct equivalent to the 388.
** These are not supplied with the little plastic spacer. Re-use the spacer from your old 387 mercury cell.

My watch runs fast or erratically with the new Silver Oxide Battery. What is wrong?

This is due to a phenomenon known as "double indexing". Double indexing occurs when the amplitude of vibration of the tuning fork increases to a point where the index jewel picks up 2 teeth on the index wheel, not just one as it should. The amplitude of vibration of the fork has increased because of the higher voltage of the Silver Oxide cell. For a complete description on how the index mechanism works, click here. It's well worth taking the time to read and understand this.

Can this be corrected by "re-phasing" my watch?

In many cases, the watch can simply be re-phased, and it will run fine, though very likely the built-in "safety factor" (described below) will be reduced. Occasionally, something else will need to be done to correct the problem. Many repairers used to "mix-n-match" coil sets and tuning forks to get a combination that works. Due to manufacturing tolerances, some forks vibrate at a slightly higher amplitude than others. The hope was to find a coil set/fork combination that worked ok. This can be a very laborious and frustrating process, not to mention the extra wear and tear inflicted on the movement by having to dismantle it so many times. Another method I have heard of is that some repairers increase the tension on the index and pawl fingers, hoping that the increased load will reduce fork amplitude. Needless to say, this is a practise which can only have disastrous consequences in the long run, as it will eventually destroy the index wheel. In 218 watches, double indexing can be a result of the index wheel not running true. In this case, there is really no option but to change the index wheel. Alternatively, use an Accucell 1 battery.

There is a better way of solving this problem

One of the problems of both the re-phasing and the mix-n-match technique of solving the double-index problem is that the "safety factor" built into the index mechanism is lost. This "safety factor" is the difference between the vibrational amplitude when a fresh cell is installed, and the amount of amplitude required to cause double-indexing. The safety factor is necessary to stop normal daily wear and tear and knocks causing the occasional double-index, and thus causing the watch to slowly and intermittently gain. There is only one way to satisfactorily solve this problem. This is to fit a regulating device to the watch which drops the voltage supplied to the Accutron electronics to a level it was designed for. In this case, the Accucell 1 solves this problem.

What are Accucells?

Since the first generation Accucells came onto the market some 10 years ago, they have undergone a process of refinement and development. I am now pleased to report that the "2nd Generation" Accucells that are now available are a significant improvement on the original design, and in fact now embody the same electronic principles that I used in doing coil modifications to Accutrons to make them compatible with Silver Oxide cells. Hence, they now deliver the correct voltage to allow an Accutron to start and run within their original design specifications. In fact, I am inclined to think that Accucells are now a more satisfactory solution than the coil modifications which I proposed in the past, especially for those watches which won't readily adjust to run on Silver Oxide cells.

There is only one negative issue with Accucells, and that is the design of the Accucell requires that a slightly smaller cell is used than the original cells, and this means that the time between cell replacement is reduced from 12-15 months to about 9-10 months or so. This is simply because the power stored in a cell is proportional to its physical size and the amount of active chemicals that can fit in it.

So, rather than modify your Accutrons, I strongly recommend that you consider using an Accucell if you are having problems with double-indexing and your watch running fast. As for owners of Omega f300 watches, and others that are based on the same movement (ESA 9162, ESA 9164, ESA 9210, and the micro-motor tuning fork watches Omega cal 1220, cal 1230 Megasonic f720hz), there should not be a need to use Accucells, as those movements were designed to run satisfactorily on the higher voltage Silver Oxide batteries as well as the Mercury based batteries which have been phased out now. However, running the Omega 1220 on Accucell-1 is recommeded, to keep wear and tear down on the micromotor.

If you wish to purchase Accucells, (manufactured by Clark Watch Parts), please visit their Ebay store here. Their ebay user name is nostalgia-2000. I have no affiliation at all with Clark Watch Parts or Nostalgia-2000 on Ebay.