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WeinCell MRB400 Non-Mercury Replacement for PX400 EPX400 RM400 H-B V400PX E400N


Type: Zinc Air. Voltage: 1.35 V.

Diameter: 11.2 mm (9.6mm without collar). Height: 3.6 mm.

Price: 6.50 each. 6.10 each if you buy two or more. Postage and packing included.

1.35 V Replacement for: PX400 / EPX400 / RM400 / H-B / V400PX / E400N / PM400R / KX400 / T400N.

The Wein Cell MRB400 is a 1.35 volt non-mercury battery. It is designed to replace Mercuric Oxide RM400 (and PX400, EPX400, RM400, H-B, V400PX) batteries and is commonly used in cameras and exposure meters. The Wein Cell MRB400 can be used in the Pentax Spotmatic, Spotmatic II, Spotmatic IIA, SP500, SP1000, and many more. The Wein Cell MRB400 is NOT suitable for watches (for watches consider our Accucell-1.

The Wein Cell MRB400 has a distinctive appearance with its black plastic collar. 

The WeinCELL MRB400 is a custom zinc/air battery designed to replace banned mercury batteries. Unlike 1.5v alkaline replacements whose unstable output can produce exposure errors, WeinCELLs deliver the same 1.35 V voltage and stability of output as did the mercury batteries. In contrast to hearing aid batteries which only last 1 month, the WeinCELL MRB400 batteries last much longer, some times up to a year. To achieve this longer life, the MRB400 uses a proprietary electrolyte and has only two small air holes, rather then the 7 larger holes found in standard hearing aid batteries.

To use the WeinCELL MRB400, the adhesive tab must be removed. This allows air to enter the cell. After about 30 minutes, the MRB400 is fully activated and ready for use.

An alternative mercury free replacement for the PX400 is the silver oxide S400PX. These S400PX cells produce 1.55V which is higher than the 1.35V produced by the original PX400 mercury cell. Because the S400PX 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.

Possibly the 'Rolls Royce' of replacements is the H-B adapter fitted with a silver oxide 377 cell. The H-B adapter is specifically for the Spotmatic range of cameras and replaces the battery compartment cover. It has a recess into which a 1.55V silver oxide 377 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 H-B adapter is expensive, but it can be reused time and time again with inexpensive silver oxide 377 cells. Over time you may find the H-B adapter will actually save you money over the other options. The drawback is replacing the original battery compartment cover with a replacement and reducing the authenticity of the camera. 

The WeinCELL MRB400 battery has a shelf life of up to ten years. Why not buy two or more, take advantage of our reduced price and make sure you are not left without a camera next time your battery runs out.

* Actual manufacturer may vary depending upon availability

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