Mercury 625 batteries

I found a few that I must have bought just as they were being discontinued. "Crown" brand - so not a first tier brand.

Tested on yesterday with voltmeter - still reads 1.35v. Impressive longevity; too bad they were mercury based. At least I can dispose of them at the household hazardous waste site after I've used them. Though only my Rollei 35 sill uses those batteries.

I think they still make them in Russia.

A voltage reading alone doesn't tell us much. Dry cells usually read approximately their design voltage under no load, even when they’re nearly depleted and unable to produce a useable current. A proper battery tester for dry cells and multi-celled batteries measures the current from the cell or battery under the load of an appropriate-value resistor.

I use my Radio Shack battery tester for this purpose. It is an older-style device of the d’Arsonval type that uses a needle that sweeps across a scale denoting the condition of the cell or battery. To use it, you must set the selector to the type of cell or battery being tested.

One of the advantages of mercury cells was their long usable storage life. These generally lasted much longer than other types.

My battery tester also shows these as "good". Though on the low end of good. However, the tester assumes a 1.5v button cell, not a 1.35v.

In that case, your old mercury cells might still be of sufficient strength to power your camera correctly at 1.35 volts.

There are availble voltage convertors which are physically sized the same as PX-625 mercury cells, but they have an opening in the center which take 1.55V silver oxide cells. The voltage convertor takes the 1.55V and regulates it down to 1.35V needed by many older cameras. (Some meter circuits are not affected by higher voltage, but many meters give wrong readings which cannot by simply compensated by using a different ISO setting!) These voltage convertors are called 'MR-9' convertors.

Beware there are so-called 'MR-9' which are NOT 'voltage convertors'...the are simply physical holders for air zinc cells (hearing aid battery) which immediately begin to deplete once the air seal is removed, even if the camera is never turned on or never used. Make sure the product you buy does VOLTAGE CONVERSION of a silver oxide cell.