PX625 / PX13 / MR9 Mercury Cell

Type: Mercuric Oxide. Voltage: 1.35 V.

Diameter: 15.6 mm. Height: 5.95 mm.

Also known as: PX625 / PX13 / EPX625 / V625PX / MR09 / MR9 / H-D / HD / RPX625 / RM625 / KX625 / HD1560 / 1124MP / Mallory RM-625R / Eveready E625N / Burgess HG-625R / 4370 / 4371 / V13PX / EPX13 / V625PX / HD625 / PN625 / RM625 / 4625 / 625 / H1560 / HD-D / M01 / M20 / 8930 / Varta 7002 / Pertrix 7002.

Comments:
The MR9, PX13 and PX625 is is a discontinued Mercuric Oxide coin type cell that was commonly used in cameras and is now banned because of toxicity and environmental fears.

The original PX625 mercury cell produced 1.35V.

There are three possible mercury free replacements for this PX625, PX13 or MR9 cell:

genuine Mercury cell, the PX625, PX13 or MR9 - but they are rare and hard to find.
the equivalent alkaline cell, the LR9 or V625U.
the equivalent silver oxide cell, the S625PX.
the equivalent zinc air cell, the WeinCELL MRB625.
a voltage reducing adapter, the MR-9 adapter and a silver oxide 386 cell

The least expensive PX625 replacement is the alkaline cell, the LR9 or V625U. They fit perfectly but, as with all alkaline cells the voltage is not stable, it drifts down from 1.5V towards 1.35V (the voltage of the original Mercury cell) and then lower still. If you use the cell in a camera that needs a steady reference voltage, as the voltage is not steady throughout the useful life of the cells, you need to constantly adjust how you compensate.

Because the S625PX silver oxide cell produces a steady 1.55V, you are able to compensate for the higher voltage by a fixed number of stops or by adjusting the ASA setting. There may be as many as two f-stops underexposure by a camera that uses 1.55v instead of the original 1.35v, but the compensation you require is constant.

Another PX625 replacement is a zinc air battery. The WeinCELL MRB625 is a custom zinc/air battery designed to replace banned mercury batteries. WeinCELLs deliver the same 1.35 V voltage and stability of output as did the mercury PX625 batteries so there is no need to adjust your exposure. The WeinCELL MRB625 batteries last much longer than hearing aid batteries, some times up to a year. To achieve this longer life, the MRB625 used a proprietary electrolyte and has only two small air holes, instead of the 7 larger holes found in standard hearing aid batteries.

Possibly the 'Rolls Royce' of replacements is the MR-9 adapter fitted with a silver oxide 386 cell. The MR-9 adapter is the shape and size of a PX625 cell, has a recess into which a 1.55V silver oxide 386 cell can be dropped and and contains voltage regulating electronics to drop the voltage to match the 1.35V of the original mercury cell. The MR-9 adapter is expensive, but it can be reused time and time again with inexpensive silver oxide 386 cells. Over time you may find the MR-9 adapter will actually save you money over the other options.

Once in a blue moon we have old stocks of genuine mercuric oxide PX625, PX13 or MR9 cells; see 'stock status' below for current availability. These PX625 cells will have been in the supply chain prior to 18th September 1992. Since then it has been illegal to manufacture or to import PX625's. This puts our PX625's outside their ten year shelf life and so more than 85% of their energy content is likely to have dissipated. We keep our PX625 cells refrigerated to minimise self-discharge, but still, we find it necessary to sell these PX625 cells on an 'as-is' basis and can not accept returns.

We ask our customers of PX625 cells to dispose of mercury cells thoughtfully. Local authorities operate recycling facilities and we are happy to receive batteries for safe disposal, even those that we have not originally sold.