I have at least two cameras that take the now-outlawed PX625 mercury battery, a
Rollei 35S and a
Canonet G-III QL17.
If you have a camera that originally took mercury batteries, there is some
excellent information out there about the different voltage characteristics of the various types of replacements, and what your options are. I've heard good things about the
C.R.I.S. adapter but haven't tried it yet, and I don't think the voltage drop-off of the alkaline replacements is worth having my meter adjusted for the higher voltage. I've been using the
Wein replacement zinc-air battery with excellent results, but they're not cheap and only last a couple of months.
It also so happens that I have a
Ricoh 500G that takes the much easier to find size 675 battery. Though the original battery (in both cases) was 1.35v, a modern zinc-air hearing aid battery runs at 1.4v, about 3.7% higher but
usually within safe tolerance and with the same nice constant voltage output as the mercury. I can pick up an 8-pack of a random brand on sale for under $8 USD at nearly any drug or grocery store and zinc-air batteries have a tremendous shelf life until exposed to air, so they can live mistreated at the bottom of a camera bag indefinitely. They do have a distinct, predictable lifespan once exposed to air whether under load or not, so it pays to keep several handy.
A few years ago, I stumbled across
one of the many articles that talked about how the 625 and 675 batteries are
nearly the same height, and using a rubber o-ring around a 675 will often do the trick. So, on the way home last night, stuck in traffic, I pulled into a home improvement store, rummaged through their o-rings and purchased a couple of potential candidates.
The
BrassCraft SC0535, with a 10mm inner diameter and 1.5mm thickness, worked like a charm. At $0.58 USD locally, I'm looking forward to now spending about an eighth what I used to on replacement batteries, or one extra roll of film per battery replacement. Not bad!
I also stumbled across a very geeky article (which I can't locate at the moment) that talked about hole optimization on zinc-air batteries, and it turned out that five holes is optimal for the 625/675 size battery. I have found the
Rayovac L675ZA-8ZM has five holes and is readily available. No scientific testing has been done on my part, but they do seem to be higher quality than their average price would indicate, or at the very least no lower quality than some more expensive peers.
