1.35v battery replacement (1.4v)

[richardHaw]

electricals and electronics are my weakest suite. I am allergic to anything electonic/electrical after frying the family Betamax in the '80s when I was attempting to fix it and got electrocuted (not pleasant, almost died) while fixing the transformer for my family computer

I found some cheap hearing aid 1.4v batteries. I think .05v shouldnt matter much so I will want to give it a try. what do you guys think? anybody tried these? The ones I saw are alkaline which has a smooth voltage curve until it hits zero. zinc would be nice since the curve falls sharply.

any advise will be welcomed.

[Hugh_3170]

Richard, I have tried 1.4V hearing aid batteries in the past and they did not prove stable enough for my Nikkormat bodies.

The simple metering circuitry for the Nikkormats were sensitive to voltages that were not the 1.35V that they were designed to work with. 

On the other hand, the humble Pentax Spotmatic circuity was more complex and balanced and was designed to work accurately with cells of voltages in the 1.35V to 1.55V range, so if you are into Pentax Spotmatics, there should be no problem.

[pluton]

Richard, You didn't mention which mercury battery you are looking to replace, but I found this commercial U.K. site which lists several alternatives to the old PX-13 and PX-625 cells.
http://www.smallbattery.company.org.uk/sbc_px625.htm

[Matthew Currie]

Fortunately the Nikon Photomic FTn meters were pretty easy to recalibrate for silver oxides, so mine are set for those.  Unfortunately it's become quite hard to find the big batteries in silver oxide now, so I had to make little metal rings to fit smaller ones.

Hearing aid batteries are usually zinc-air (which I think performs better under heavy load).  If they have a pull tab, they're zinc air for sure.  I've used hearing aid batteries in Konicas, which are both difficult to adjust and very intolerant of voltage variation, and found they worked pretty well with an added 2/3 stop ASA offset.  They don't last very long, and it takes a day or so for the voltage to stabilize, but it then stays pretty constant for the duration.  The Konicas had a nice battery check which was ASA dependent, so it was really easy on those simply to run the battery check and adjust the ASA until it was right.  The result was nice and precise. 

I've  heard that you can stretch out the life of zinc-air batteries by not unblocking all the holes, and somewhere I read a recommendation to dab a little glue on all but one or two.  I never tried it, in part because I gave away my Konicas. 

Other cameras I've had worked moderately well on alkalines, seeming to be less bothered by the voltage variation,  and again if you have a standard against which to measure the reading, you can adjust the ASA to correct for voltage.  I've had some alkaline batteries that went fairly quickly down to 1.35 volts and then stayed there for a long time.  It's hard to predict, but it can come surprisingly close.  It's always good to try them, because some meters are not all that accurate anyway, and sometimes you get lucky.  I had a Yashica Minister that was spot on with an alkaline.

The Pentax spotmatic, as mentioned, is not voltage dependent and will work with modern batteries if you can get the right fit. 

Unfortunately, the Nikon Photomic uses a side contact for the battery, so you can't just use an O-ring on a smaller size, but on some cameras with contacts only at the ends, you can.

[benveniste]

The menu of bad choices seem to be:

• Recalibration to Silver Oxide (not possible with all cameras)
• WeinCell MRB625 (Expensive, short life once activated)
• http://www.px625.ru/ (Expensive, dubious legality, environmental concerns)
• MR-9 Adapter (https://shop.criscam.com/products/mr-9-mercury-battery-adapter?variant=998679497) (Buy once, cry once, smaller battery)

[Hugh_3170]

On a slightly positive note, the Wein cells can be made to last longer by removing them from the camera when not in use and resealing them against the air.

Still a nuisance to have to do this I admit.

[Matthew Currie]

The menu of bad choices seem to be:

• Recalibration to Silver Oxide (not possible with all cameras)
• WeinCell MRB625 (Expensive, short life once activated)
• http://www.px625.ru/ (Expensive, dubious legality, environmental concerns)
• MR-9 Adapter (https://shop.criscam.com/products/mr-9-mercury-battery-adapter?variant=998679497) (Buy once, cry once, smaller battery)

I would add to that the solution that can work on some, if not all, cameras:  offsetting the ASA/ISO.  I found Konica T with two batteries took a lot of offset, but some others aren't so bad, and it depends on what film you're using.   As I recall, the Nikon Photomic was about two stops off, and some are less.  If you use silver oxides or fresh alkalines, the amount of offset will be consistent, so all you have to do once you've figured it out is to write it down. 

I tested meters by setting the camera up on a tripod aimed at a uniform off-white wall lit evenly.  A known-accurate Minolta X-370 gave the correct reading, and I could either adjust the ASA or the meter itself on any camera by aiming it at the same wall with a similar focal length lens.   It's a simple and not very technically fancy way to do it, but I got good results given the relatively primitive meters I was starting with. 

[richardHaw]

thanks everybody!
here is a follow-up question 

is adding a diode on the camera/meter better than using adapted batteries?

I recall an electrician telling me that using adapted batteries will be better because you dont overload the circuit. sorry, i am really dull when it comes to electronics.

[JCDowdy]

I have some old film cameras I am thinking of playing with, so your question got my attention.

Here is a link to an article I found on a well known archive that seems very informative.
http://www.butkus.org/chinon/batt-adapt-us.pdf

[JCDowdy]

Found another rather nice looking solution.  No diode but appears to solve fit issues.
See:  http://www.paulbg.com/Nikon_F_meter_batteries.htm

[Matthew Currie]

Found another rather nice looking solution.  No diode but appears to solve fit issues.
See:  http://www.paulbg.com/Nikon_F_meter_batteries.htm

I use metal rings on my Photomics (in this case recalibrated ones using silver oxide).  They work just fine.

[Ann]

I have used a similar adapter sleeve to the C.R.I.S. in Sekonic meter. It worked very well.