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Re: Battery conversion, Was [OM] A sad OM-1n story

Subject: Re: Battery conversion, Was [OM] A sad OM-1n story
From: dreammoose <dreammoose@xxxxxxxxx>
Date: Wed, 03 Apr 2002 15:32:28 -0800
The history is simple. Mercury batteries have the most stable voltage through their useful life, so many camera and light meter manufacturers used them. Light metering with mercury batteries tend to be very accurate and stable until they go and then the meter just quits. Thus no bad exposures, but the need to carry a spare. I had the battery in my OM-1 go out in Guanajuato, MX almost like a switch being pulled many years ago. I sucessfully used the exposure guide from the film box until I found a new battery a few hours later.

More recently, environmental concerns led to outlawing mercury battery production in the US. I think all production in Europe has stopped now, too, but there are still some Varta cells floating around. The problem is that mercury cell voltage is 1.35v, while the 625 size cells used with other technology are about 1.5v. This leads to a significant exposure error (2 stops?). As long as your mercury battery lasts or you can find others, you are fine. When you put in the spare, it's time to start looking at alternative battery solutions.

Threre are several solutions. When you have your camera CLAed, the meter is adjusted anyway and can simply be adjusted for the higher voltage. This adjustment can also be done by itself. There is a thingy called an MR9 adapter, which is the shell of a 625 battery with a shottsky diode and plastic plug in it which holds a 357 silver oxide battery. The diode forward voltage drop adjusts the voltage and the whole thing fits where the mercury 625 battery went with no adjustment or modification of the camera. There are available from John H at www.zuiko.com . Handy tinkerers can just insert a shottsky diode in the meter circuit in the camera.

I have heard mentioned a few times about this battery conversion,
I was wondering if someone could explain it to me (why it is done etc)

When I bought my om1 the man in my local shop put a new battery in
it saying the one in there was the wrong type.
Also bought a spare from him. Do i need to get mine converted?
The new battery is a mercury one i think
Thanks



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