All About Watch Batteries.

Most watches on the market run on small button cell type batteries, (although there is a growing market segment of smart watches that use rechargeable lithium cells.)

These batteries occasionally need changing, and the prices can vary greatly depending on where you take your watch. They also have vastly different run times based on size and intended use. But they all have one thing in common - they should be changed by someone with the right tools and know-how. 

There are two major types: Silver oxide, and Lithium, and in silver oxide they come in both high drain and low drain. The correct type will depend on your watch. There are also different spec levels of batteries. I use Renata Swiss batteries, and I can offer factory original spec in certain sizes. These have a higher silver content than standard, and offer the longest possible run time. They also cost more.

Below is the process I go through on a moderate quality watch when replacing the battery.

This watch has stopped, so my basic assumption is that the battery is due for replacement. It has a water resistance rating of 100m, so I will also check the seals and pressure test the watch afterwards.

On this watch the back is threaded, and screws onto the case. I mount the watch in a dedicated case vice to securely hold it while I unscrew the back with a Swiss case-back tool. I have a few different models for different case type, and also different size case vices. The cloth is to prevent accidental damage to the case, and it helps prevent slippage.

As the case back comes off all the dirt that had accumulated around the case back seal loosens and drops into the watch. It is very important that all this grit is removed. If not it will very soon end up inside the movement. I also remove the stem and crown so we can check for rust on the setting stem, clean around the crown and case tube, and re-lubricate the rubber o-rings.

It is very common for other shops to skip these steps entirely.

The parts are all cleaned up and the old battery has been tested and discarded. There is a new o-ring in the grease pad where a light coating of silicon grease is applied and it is all ready to go back together. The customer has opted for the longer run time factory spec battery.

The battery is signed and dated with a sharp tweezer point, and then carefully fitted.

With the new battery, and the stem and crown installed, the case back is re-fitted and the watch is pressure tested in a Swiss automatic air pressure tester.