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Old Mar 12, 2005, 7:39 AM   #1
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Hello all.....Does anyone have any info on what may be used to replace the Merc type PX 13 batts in the Luna Pro. I have searched and found many with the 4145 Battery adapter supplied by BOGEN from B&H but have been out of stock for months. I have also heard that using the alkaline replacement batts does not give accurate readings at all on the meter. There is also an MR-9 adapter kit for each battery with a cost well above 60.00 for both batts w/ shipping and does not include the silver oxide replacements. I am also aware of the Wein Air cells but are also hard to come by locally and do not provide too much life. Is there anyone using a different source for their older Luna Pro? Any suggestions would be well appreciated. Is the Alkaline theory a myth? There is also text under the battery compartment of my LUNA that is printed "IEC MR 9" Anyone have this or knows what it is? Thanks for replies.
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Old Mar 29, 2005, 3:43 PM   #2
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Hi,

I've got the same batteries problem and questions with a Gossen Luna Pro I just purchased off eBay. It needs the Mallory PX 13 or 625 Mercury Battery replacements. I've tried some 625's from Radio Shack, but they're 1.5 volts and I've suspected this is not correct for the meter readings. Did you get any answers that help on Steve's Digicams site?

Thanks for whatever guidance you can give.

Gpaige3 in Colorado
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Old Mar 29, 2005, 5:40 PM   #3
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I ended up purchasing replacement batts that were the 625a's. They do work as time progresses and the batts lose the strength to get me into the red zone. Right now it is about [2] stops off on the reading and find that I do have to compensate and use judgement calls instead of metering. There is an adapter sold through many camera shops such as B&H if you do a google for MR9 or GOSSEN Battery adapter. This will reduce the voltage of the 1.5v to the required 1.3v. It is rather expensive at 39.00- 42.00 + Shipping but will also let you use your LUNA. There are other posts that have stated that their GOSSEN was ent into BOGEN for a complete check-up and that they added the adapter with no charge. If you do order the adapter, it does come with the right batteries for the unit that can be purchased anywhere. Hope that helped.
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Old Apr 4, 2005, 2:50 PM   #4
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You might have noticed batteries with mercury are banned in the United States due to environmental safety. The reason for the ban was to prevent anymore buildup of the toxic components of mercury batteries in our soil and water.

A characteristic not shared by present day alkaline cells or any other batteries, mercury batteries maintain a very constant voltage over most of their life. A mercury cell has an initial voltage of 1.35V that it holds until the last 5% of its life and then the voltage declines rapidly. The Luna Pro did not need a battery voltage regulator circuit because the mercury battery voltage was so stable the meter simply did not need voltage regulation. And it was nice that mercury cells can last for 10 years or more in storage. Believe it or not I've had the same mercury cell in my Luna Pro since 1980 and using the Luna Pro battery check I still have over 50% power in the mercury cells.

Unfortunately, banning the use of mercury cells was short sighted of the government and we now have a lot of useful and expensive equipment that cannot be used by present day batteries. My favorite light meter because of its durability is the Luna Pro.

Other cells will work in the Luna Pro but since the voltage is too high and do not have the discharge characteristics of a mercury cell the Luna Pro will never work properly. The higher voltage of the alkaline cells will make the meter read too high. The sloping discharge of the alkaline cells means the meter will never consistently give a light meter reading.

I've supplemented my Luna Pro with back up mercury cells. A couple of years ago my friend went to the UK and brought me back some cells. Last year I had a relative send me mercury cells from Mainland China.

I don't know if the mercury cells are manufactured anymore but they are available if you know where to look for them.
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