Most old cameras, including the Spotmatic series, make use of 1.35V mercury cells for powering their built-in exposure meters. Such batteries are now discontinued for environmental protection.

More than twenty years ago, when many production cameras still used mercury cells, you could find them everywhere in the world. On the contrary, lithium batteries were only managed by Kodak at their own premises "due to high pollution in case they are dispersed in the environment". Nowadays, mercury cells are discontinued for environmental protection, while lithium batteries (most used by current equipment such as cameras, cellular phones, etc.) are widely available everywhere in the world. Is it possible that mercury pollution danger raised during the years (when equipment using them decreased so much) while lithium pollution decreased (when equipment using them increased so much)? I strongly doubt it. However, that's the way things are in our crazy world.

So in practice mercury cells are no longer available. In order to replace such old batteries, some people modified the battery compartment of old cameras for accepting 1.5V silver oxide cells (both mechanical and electrical modifications could be necessary), while others adapted smaller watch-type 1.35V zinc-air cells (only simple mechanical adaptation necessary).

According to information from Gene Poon from Spotmatic discussion group such 1.35V voltage cells can be replaced in the Spotmatic series cameras with any matching 1.5V battery (silver oxide type are good). That's because original SP, SPII, SPIIa, SP500, SP1000 all use a bridge circuit where the meter measures the balance between the two legs of the bridge. Both legs of the bridge would be equally affected by any "normal" voltage variations. SPF uses a dual coil meter, the two halves equally affected by any voltage variations.

In case you want to stick to 1.35V, probably the best solution is using dedicated zinc-air cells, giving correct voltage (1.35V) and having proper size, thus meaning no special adapters required and maximum battery life.

When using zinc-air cells, they have to be activated by removing protective labels on them, allowing air to enter the cells. Be sure not to activate zinc-air cells before actual use, since once activated the battery will last one year no matter how much you use the camera. That's the drawback of zinc-air technology and the reason for using mercury cells in the past. Storage life of non-activated zinc-air cells is stated to be ten years.

And now the most important question: where can you find dedicated zinc-air cells for your beloved camera? As far as I know, currently they are only manufactured by Wein Products, and distributed worldwide by Micro-Tools (www.micro-tools.com). By visiting their website, you can access your world region and in case order your battery online. However, since Micro-Tools is the world's largest supplier of camera repair tools and supplies, you can also get WeinCells via your favorite photo repair lab.

Don't expect bargain prices: after all worldwide demand for such batteries is quite low and Wein has monopoly on them. As a reference, currently (April 2003) Micro-Tools European website sells WeinCells at 8.12 Euros each.

Here is a table with most common vintage cameras using mercury cells and their WeinCell replacement models: