Railfan Technology > S76 button battery replacement

I own a handy Minolta Flashmeter III which is also a great ambient meter. The problem is it uses 6 of the S76 batteries in a stack which are no longer made account they conrain mercury. When I got the meter out a couple of weeks back to do some scenic work I found the batteries were too weak to provide readings.

I did some internet searching and found there is a replacement in the Energizer 357 BPZ battery. These are 1.55v silver oxide cells. A 3 pack sells for about $6 making it about $12 to get my meter back in service. No where did I find a direct statement about that but they are the same physical dimensions and the 1.55v output meets the other requirement.

S76 cells were very popular in photographic equipment at one time so the 357 batteries might be a way to bring a retired piece of equipment back to service.

Mercury batteries were preferred in simple exposure meters because of their constant voltage over time.  But:

"Depending on the circuits in an exposure meter a constant voltage is actually necessary or not. A Pentax Spotmatic, for instance, has a ‘bridge’ measuring network and does not need an exact 1.35 volts. This camera works perfect on a 1.55 volts alkaline or 1.6 volts silver-oxide cell. When an alkaline or silver-oxide cell is used instead of a mercury cell without an adapter or other special measures, deviations of up to 4 Light Values! (Konica TC) can occur."

https://www.nadir.it/pandora/PILE-PX625.pdf

There is also an EPX76 silver oxide replacement which has a higher capacity.


With regard to any EV differential I will need to take the meter outdoors on a sunny day and try some calibration exercises. The meter has a screw adjustment if needed. This Minolta meter was designed and built to pro quality.

More digging finds the S76 batteries were 1.55v batteries not the 1.35v output of a mercury cell.



Edited 1 time(s). Last edit at 09/23/18 11:56 by fbe.