A battery question about older meters

[TXForester]

I'm thinking of getting an older meter like an Sekonic Zoom L-288. It uses the old PX-13 batteries. I know there are adapters for using the newer replacement batteries for cameras that use this battery.

If a meter such as this one calls for two PX-13 batteries, can two newer batteries with two adapters be used?

Also, this type of meter can be zeroed (calibrated). Is it possible to use two of the newer batteries (without adapters) and zero the meter to compensate for the higher voltage?

Thanks for any help.

 

[sevo]

If a meter such as this one calls for two PX-13 batteries, can two newer batteries with two adapters be used?

Yes - you'd use two adapters. The voltage drop of a Schottky drop diode is almost constant, you could either use one 0.4V drop diode or two 0.2V diodes to bring the double silver 3.1V to double mercury 2.7V. That is, if you make your own adapter or solder a diode into the camera, you'd save space picking one with about 0.4V drop - but AFAIK there are no readymade adapters with these being sold right now.

Also, this type of meter can be zeroed (calibrated). Is it possible to use two of the newer batteries (without adapters) and zero the meter to compensate for the higher voltage?

No - the zero setting adjusts the zero point and should not affect the scaling. A few meters have a additional internal scaling/adjustment pot and these can be readjusted to another battery type - but that is rather uncommon.

Oh, and do read up on the Sekonic Zoom 288 before you buy one. It meters across the full finder area and is NO useful substitute for a spot meter, and in my opinion it is considerably overpriced for a mercury cell meter with optical finder - the contemporary Sekonic View Spot L-438 tends to be similarly priced, is a 2° spotmeter and takes a regular AA cell!

Sevo

 

[Landshark]

I believe there are adapters available for two cells as well as one.
The two cell adapter was used in the Nikon meter heads and the older gray Luna Pro meter.

 

[TXForester]

Thanks Sevo and Landshark.

 

[zauhar]

You can get a direct replacement for the PX-13 from B&H photo :

http://www.bhphotovideo.com/c/product/96457-REG/Wein_W9901201_MRB625_Cell_1_35v_Zinc_Air.html

Randy

 

[ferider]

Problem with the Wine cell is the different shape of the current curve over time, when compared to the original Mercury batteries.

I use this double adapter that works like a charm. Worth the money for me.

http://www.bhphotovideo.com/c/product/89868-REG/Gossen_GO_4145_Adapter_Kit_Battery_Holder_for.html

Roland.

 

[zauhar]

Problem with the Wine cell is the different shape of the current curve over time, when compared to the original Mercury batteries.

I use this double adapter that works like a charm. Worth the money for me.

http://www.bhphotovideo.com/c/product/89868-REG/Gossen_GO_4145_Adapter_Kit_Battery_Holder_for.html

Roland.

So that thing fits in the battery compartment without modification of the meter?

Randy

 

[ferider]

It does for my Gossen, Randy. The batteries are normally stacked upon each other.

Similar to a Chris adapter using a diode - just for two silver oxide batteries.

 

[TXForester]

That adapter should work with cameras that would take stacked PX13/PX625 cells too.

 

[zauhar]

I just got my LunaSix back from its second trip to Mr. Milton. I might consider getting that adapter - although so far the "fake" mercury cells seem fine. Roland, what is the issue with the Wien cell characteristics?

Thanks!

Randy

 

[ferider]

I just got my LunaSix back from its second trip to Mr. Milton. I might consider getting that adapter - although so far the "fake" mercury cells seem fine. Roland, what is the issue with the Wien cell characteristics?

Thanks!

Randy

Hi Randy,

I've used Wein cells and hearing aid batteries (the latter with a brass ring to make them fit mechanically). My biggest problem with zinc-air batteries is that they are dead after a few months, even without usage (they "air out"). I have too many cameras I guess, so that some don't get used for a few months ( 😱 ), making me prefer Silver Oxide.

Roland.

 

[wolves3012]

Yes - you'd use two adapters. The voltage drop of a zener drop diode is almost constant, you could either use one 0.4V drop diode or two 0.2V diodes to bring the double silver 3.1V to double mercury 2.7V. That is, if you make your own adapter or solder a diode into the camera, you'd save space and money picking one with 0.4V drop - but AFAIK there are no readymade adapters with these being sold right now.

Sevo

Zener diodes aren't generally used in this way at all, you probably mean a Schottky diode. Using a Zener would result in very poor battery life since they're used as shunt regulators and are only available from about 1.2V upwards. Schottky diodes give a voltage drop between about 0.15-0.45V so you'd use them in series.

There is still the issue that silver oxide and alkaline cells don't give a stable voltage as they discharge, unlike mercury cells. Unless the original circuit was designed to cope with the change (some were, some weren't) then drift is unavoidable.

 

[sevo]

Zener diodes aren't generally used in this way at all, you probably mean a Schottky diode.

Right. Post corrected...