The Wein Cell MRB400 is a 1.35 volt non-mercury battery. It is designed to replace Mercuric Oxide PX40, RM400 and V 400 PX batteries and is commonly used in cameras and exposure meters. The Wein Cell MRB400625 can be used in the Pentax Spotmatic, Spotmatic II, Spotmatic IIA, Spotmatic 500, Spotmatic 1000, and many more.

The WeinCELL MRB400 is a custom zinc/air battery designed to replace banned mercury batteries. Unlike 1.5v alkaline replacements such as the LR9 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 used 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.

Can be stored for up to 10 years: WeinCell batteries are only activated by pulling the sticker.
Full battery voltage approx. 2 hours after removing the sticker.