Gossen Luna-Pro Battery insertion: Need some help. I just picked up the above light meter in a box of camera equipment at one of our auctions. It looks like it is in great condition. I...

copladocus

Need some help. I just picked up the above light meter in a box of camera equipment at one of our auctions. It looks like it is in great condition. I found 1.35 volt batteries at B&H and they will fit. However, looking at the diagram for inserting the batteries it does not indicate which side is the positive side. The new batteries are not exactly the same profile as the originals depicted in the diagram. I have searched the internet and even downloaded and READ the Gossen manual and nowhere does it tell me, literally, which side is up. As this is a fine instrument I don't want to potentially ruin the electronics by inserting the batteries the wrong way. So my one and only question, does the positive terminal face the removable screw plug or do they face down into the well of the battery compartment? Thanks ahead.

Orphoto Loc: Oregon

Usually it says on the inside of the lid in itty bitty type.

OnDSnap Loc: NE New Jersey

copladocus wrote:

Need some help. I just picked up the above light ... (show quote)

Positive side is always the side with the bump/ hump, or smaller diameter. Side with lettering is negative.

Gene51 Loc: Yonkers, NY, now in LSD (LowerSlowerDelaware)

copladocus wrote:

Need some help. I just picked up the above light ... (show quote)

If you got the Wein MRB625, the battery is two parts of different diameters. The smaller diameter is - and the larger diameter is +. You put the batteries in with the wider diameter on the bottom. But once you pull the tab the cell discharges fairly quickly. Some tape over the 2 small holes when not in use, claiming the batteries last a little longer. A longer term solution is to use an adapter so that you can buy LR44 batteries, which are more commonly available and a lot cheaper.

https://www.amazon.com/FASTROHY-Battery-Adapter-Replacement-Exposure/dp/B08CSMCQ4G/ref=sr_1_3?gclid=Cj0KCQiAkNiMBhCxARIsAIDDKNW4mMcyQ3XaG6yG5zdzTdBcUeTP36MDKLl1ZgZM9y01wxcK8n4SrbMaAiOwEALw_wcB&hvadid=410076144137&hvdev=c&hvlocphy=9007515&hvnetw=g&hvqmt=b&hvrand=10206124278007185255&hvtargid=kwd-297215527144&hydadcr=18471_11409391&keywords=mr-9+battery+adapter&qid=1637234543&qsid=130-0603762-4787751&sr=8-3&sres=B08CSMCQ4G%2CB0836TCPBT%2CB07XT7KVV6%2CB07FCZZ5JF%2CB07MKYMD7T%2CB00PVWQS30%2CB07XXSLHPB%2CB07XXT4HYG%2CB07VCZZPS6%2CB07JCPG9YN%2CB00HWFCAYK%2CB00009VQJ7%2CB01AXIEDX8%2CB081YX7HN6%2CB09749CHLK%2CB096NCTFSG&srpt=BATTERY

There is also this solution that not only lets a smaller batter fit in the light meter, but it also reduces the voltage so re-calibration is not necessary.

https://www.smallbattery.company.org.uk/sbc_mr9_adapter.htm

Gene51 Loc: Yonkers, NY, now in LSD (LowerSlowerDelaware)

OnDSnap wrote:

Positive side is always the side with the bump/ hump, or smaller diameter. Side with lettering is negative.

Not the Wein MRB625 if this is what he got:

https://weinproducts.com/news/entry/istherefinallyareplacementformercurycellsitlooksthatwaybutitsuretooksomedoing

You'll see that the anode - smaller diameter - is on top. Anode is always negative. Cathode, on the bottom, is always positive.

dpullum Loc: Tampa Florida

Rational Guess: Old batteries are rarely not completely dead-dead. Using a digital meter that requires no current flow you will get some indication of +/- even tho the voltage may be very low.

OnDSnap's diagram shows the typical... outer case as being negative.

Gene51 Loc: Yonkers, NY, now in LSD (LowerSlowerDelaware)

dpullum wrote:

Rational Guess: Old batteries are rarely not completely dead-dead. Using a digital meter that requires no current flow you will get some indication of +/- even tho the voltage may be very low.

OnDSnap's diagram shows the typical... outer case as being negative.

Nope!

https://weinproducts.com/news/entry/istherefinallyareplacementformercurycellsitlooksthatwaybutitsuretooksomedoing

therwol Loc: USA

Gene51 wrote:

If you got the Wein MRB625, the battery is two par... (show quote)

This battery adaptor is the same as the one in your second link, but you can buy it in the US. Considering the pound to dollar and higher shipping from the UK, I think you come out even on price and would get the adaptor more quickly from the US source. (Cris Camera in Arizona.) The ability to use silver oxide (386) batteries is a plus. They have a relatively flat discharge curve.

https://shop.criscam.com/products/mr-9-mercury-battery-adapter

Gene51 Loc: Yonkers, NY, now in LSD (LowerSlowerDelaware)

therwol wrote:

This battery adaptor is the same as the one in your second link, but you can buy it in the US. Considering the pound to dollar and higher shipping from the UK, I think you come out even on price and would get the adaptor more quickly from the US source. (Cris Camera in Arizona.) The ability to use silver oxide (386) batteries is a plus. They have a relatively flat discharge curve.

https://shop.criscam.com/products/mr-9-mercury-battery-adapter

Exactly - I just posted the one out of convenience. I remember it was an MR-9 and this was the first result in the search. Some are cheap and have no voltage reduction, like the first one I posted the link to. The better one has been modified with diodes to reduce voltage.

Thanks for clarifying.

E.L.. Shapiro Loc: Ottawa, Ontario Canada

https://www.butkus.org/chinon/flashes_meters/luna-pro_sbc/Luna-pro_sbc.pdf

https://www.butkus.org/chinon/mercury_replacement_batteries.html http://

www.photoethnography.com/ClassicCameras/batteries.html

https://www.butkus.org/chinon/flashes_meters/lunasix3/lunasix3.htm

The Luna PRO meter requires a 9 Volt battery- See excerpt from the manual attached. The Luna-Six Meter takes a button battery but the original mercury battery is no longer available. There are conversions and replacement instructions in the links above.

Unless their ar were design changes in the Luna-Pro model, you may have mistaken the PRO for the SIX.

If you accidentally reverse the polarity of the battery, I don't think that will damage the meter- it just won't respond. I would, however, check with the manufacturer or distributor- both of which are still in business, This is their international website.

https://gossen-photo.de/en/application-areas-photo/

BebuLamar

E.L.. Shapiro wrote:

https://www.butkus.org/chinon/flashes_meters/luna-... (show quote)

Sorry E.L. I think you're mistaken the Luna-Pro for the Luna-Pro SBC which has 9V battery. I believe the Luna-Pro still has mercury battery.

E.L.. Shapiro Loc: Ottawa, Ontario Canada

BebuLamar wrote:

Sorry E.L. I think you're mistaken the Luna-Pro for the Luna-Pro SBC which has 9V battery. I believe the Luna-Pro still has a mercury battery.

I still have my olf Luna-Six, obviously, I use a "button" battery, however, the MURCURY batteries are no longer produced but there are substitutions that are recommended in the links I previously posted and Gen and others have mentioned

The information posted pertaining to the 9-Volt battery is from the published manual for the Luna-Pro- it mentions a 9-Volt battery and a "clip" within the meter to make contact with the battery. A link was provided for the entire manual. I never owned a Luna-Pro, so I am not sure if there was a change in that particular model or the OP mistook his meter for a Luna-Pro when it is actually a Luna-Six. ???

In any event, I am sure he now has enough information to secure the proper battery and install itcorrectly.

therwol Loc: USA

E.L.. Shapiro wrote:

I still have my olf Luna-Six, obviously, I use a &... (show quote)

Two things. This is a link explaining which Gossen meters used the 1.35 volt mercury batteries. It also explains that the OEM adaptor made by them to house two silver oxide batteries at once with voltage drop is no longer made.

https://gossen-photo.de/en/ersatz-fuer-quecksilberoxid-batterie-v625px/

But speaking of which, back in 2019, someone on this forum was having the same problem with batteries and a Luna Pro. I had one of the OEM adaptors that had been sitting in a box for many years. I gave it to him. Sorry. I only had one. The photo was taken on my kitchen table.

(Download)

copladocus

Thanks pros for all the responses. Let me clarify my issue. The batteries are clearly marked, so no issue there. I need to know if the positive terminal is on the bottom of the well or on the metal plug that screws into the body. Thanks.

E.L.. Shapiro Loc: Ottawa, Ontario Canada

copladocus wrote:

Thanks pros for all the responses. Let me clarify my issue. The batteries are clearly marked, so no issue there. I need to know if the positive terminal is on the bottom of the well or on the metal plug that screws into the body. Thanks.

According to the diagram and a close look at my meter's battery compartment, the domed side of the battery is inserted downward and the flat side is flush with the cap. I took a close look at several kinds of button-batteries I have here in my shop and the flat side is the plus side on all of them- the are marked that was as well.

The batteries I have on hand for my old meter need to be replaced, however, I put them in as per the diagram and the meter deflected properly.

Sorry for the previous confusion- the 9-Vot battery is for an entirely different model of the Luna -Pro.