PX675 / PX76 / MR44 Mercury Cell

Type: Mercuric Oxide. Voltage: 1.35 V.

Diameter: 11.6 mm. Height: 5.4 mm.

Also known as: PX675 / PX76 / EPX675 / V675PX / MR44 / NR44 / H-C / HC / RPX675 / RM675 / 1128MP / HD675 / MR1154

Comments:
The MR44, PX76 and PX675 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 PX675 mercury cell produced 1.35V.

Once in a blue moon we have old stocks of genuine mercuric oxide PX675, PX76 or MR44 cells; see 'stock status' below for current availability. These PX675 cells will have been in the supply chain prior to 18th September 1992. Since then it has been illegal to manufacture or to import PX675's. This puts our PX675's outside their ten year shelf life and so more than 85% of their energy content is likely to have dissipated. We keep our PX675 cells refrigerated to minimise self-discharge, but still, we find it necessary to sell these PX675 cells on an 'as-is' basis and can not accept returns.

We ask our customers of PX675 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.

There are five possible replacements for this PX675, PX76 or MR44 cell:

genuine Mercury cell, the PX675, PX76 or MR44 - but they are rare and hard to find.
the equivalent alkaline cell, the LR44 or PX76A.
the equivalent silver oxide cell, the 357 or SR44.
the equivalent zinc air cell, the WeinCELL MRB675.
a voltage reducing adapter, the MR-44 adapter and a silver oxide 392 cell

The least expensive PX675 replacement is the alkaline cell, the LR44 or PX76A. 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 357 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 PX675 replacement is a zinc air battery. The WeinCELL MRB675 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 PX675 batteries so there is no need to adjust your exposure. The WeinCELL MRB675 batteries last longer than hearing aid batteries, up to nine months. To achieve this longer life, the MRB675 uses a proprietary electrolyte and has only two small air holes, instead of the larger holes (some times up to seven of them) found in standard hearing aid batteries.

Possibly the 'Rolls Royce' of replacements is the MR-44 adapter fitted with a silver oxide 392 cell. The MR-44 adapter is the shape and size of a PX675, has a recess into which a 1.55V silver oxide 392 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-44 adapter is expensive, but it can be reused time and time again with inexpensive silver oxide 392 cells. Over time you will find the MR-44 adapter actually saves you money over the other options.