C.R.I.S. battery adapter

No, because mercury batteries produced a flat output until they were very nearly dead, and then they fell off a cliff, voltage-wise.

Both alkaline and silver-oxide batteries produce a much more 'curved' output - as they age, their voltage continues to drop and drop.

So not only are they the wrong voltage, they have the wrong output characteristics.

Are you *sure* you don't want to say something about Bessas being Best about now?
 
Not quite true Bill, Silver cells also have a very similar flat output which is why they are recommended for watchs and you need to use them in the adapters which are voltage droppers rather than regulators.

Lets leave Bessas out of this thread. ;)

Kim

bmattock said:
No, because mercury batteries produced a flat output until they were very nearly dead, and then they fell off a cliff, voltage-wise.

Both alkaline and silver-oxide batteries produce a much more 'curved' output - as they age, their voltage continues to drop and drop.

So not only are they the wrong voltage, they have the wrong output characteristics.

Are you *sure* you don't want to say something about Bessas being Best about now?
Click to expand...
 
bmattock said:
No, because mercury batteries produced a flat output until they were very nearly dead, and then they fell off a cliff, voltage-wise.

Both alkaline and silver-oxide batteries produce a much more 'curved' output - as they age, their voltage continues to drop and drop.

So not only are they the wrong voltage, they have the wrong output characteristics.

Are you *sure* you don't want to say something about Bessas being Best about now?
Click to expand...

Heres this graph I found. But why is Zinc-Air the farthest to the right, making it look like it will last the longest?

4viib5t.jpg
 
Silver cells have a flatter output than alkaline, but not as flat as mercury, which is part of the reason we find ourselves in the fix we do vis-a-vis the banned mercury batteries. Because mercury battery output was so flat, designers of the time did not include any type of voltage regulator circuit. Modern battery-driven electronics all assume a voltage drop over time and compensate for it.

So a simple voltage converter is good - but not great. Used with alkaline batteries, we still have the problem of relative voltage drop using a Schottky diode. Silver oxide, less so, but it still exists.

I love my vintage cameras, but still try to use an external modern meter when possible. Seems to me to be the best of all possible solutions.
 
JeremyLangford said:
Heres this graph I found. But why is Zinc-Air the farthest to the right, making it look like it will last the longest?

4viib5t.jpg
Click to expand...

I am color-blind and cannot read your graph. I wish they would not color-code them like that.
 
JeremyLangford said:
Gah. If I would have know about the battery upgrade when I was looking for a film camera, I prolbably would have found a newer camera.
Click to expand...

Aaah, but you'll then be missing the fun of using solid craftmanship that a lot of old classics (for example your minolta) offers...

Tell you what, PM Jon Goodman, tell him you need a batt. adapter for your Minolta SRT and he'll tell you first if the one he has will work or not.

If he said it'll work, his adapter is way cheaper than Criscam.

You have to admit, a one time purchase adapter for the (remaining) life of your camera is a fair deal.
 
The chemistry of both Zincair and mercury batteries is exactly the same. (As is a wein cell). The basic chemistry relies on an oxidation process to produce the joules. In a zincair, this comes from the oxygen in the air. The problem is that the holes to let the air in also allow the electrolyte to dry out and the battery will stop working when that happens. In mercury batteries, the oxygen came from the mercuric oxide which was sealed in the battery. This took some of the space of the electricity producing chemicals so the capacity was slightly lower. Hearing aids are very high consumption devices so the battery is exhausted before the electrolyte dries so this is not a problem but you do need maximum capacity. A meter is a low current device so you are better off with a sealed battery.

As a matter of interest, the camers makers could have used silver batteries but at the time they were about 10 times the cost of the mercury ones so they didn't. In many cameras (not sure about the SRTs) there is sufficient adjustment in the meter circuit to adjust for silver cells.
There is a discussion on the problem and a fix for the early Fujica SLRs on my website here. http://pentax-manuals.com/fujica/top1/st701_battery_fix.htm

Kim

JeremyLangford said:
Heres this graph I found. But why is Zinc-Air the farthest to the right, making it look like it will last the longest?

4viib5t.jpg
Click to expand...
 
That's a shame Bill because the graph shows that silver cells have the same flat output as mercury's with the possible exception that the final voltage drop is even sharper which is why watch makers have always used them even when mercury's were available. ;)

Kim

bmattock said:
I am color-blind and cannot read your graph. I wish they would not color-code them like that.
Click to expand...
 
Kim Coxon said:
That's a shame Bill because the graph shows that silver cells have the same flat output as mercury's with the possible exception that the final voltage drop is even sharper which is why watch makers have always used them even when mercury's were available. ;)

Kim
Click to expand...

Then I stand corrected. I was relying on information I had previously obtained and stored in wetware. Apparently, the gin has me in its clutches now.
 
JeremyLangford said:
Heres this graph I found. But why is Zinc-Air the farthest to the right, making it look like it will last the longest?

4viib5t.jpg
Click to expand...

If memory serves, it was the way he was testing it that made the zinc-air battery last unnaturally long or something; either way it was indicated that it would not perform similarly in the 'real world'.
 
Jon Goodman's adapters do not drop the voltage. They are to let you use a 675 air/zinc battery in place of the old 625 battery. They only adapt in size not voltage.
 
Flat is not so flat

Flat is not so flat

Kim Coxon said:
That's a shame Bill because the graph shows that silver cells have the same flat output as mercury's with the possible exception that the final voltage drop is even sharper which is why watch makers have always used them even when mercury's were available. ;)

Kim
Click to expand...

From what I turned up yesterday (after seeing 3 different graphs) silver cells do NOT have a curve as flat as Mercury cells. It seems silver oxide has around a .15 volt peak over the rest of the curve at the beginning of its life cycle which lasts anywhere from 5% to 10% of its lifespan. If a mercury cell lasts two years on the average, and a silver cell lasts a year an three quarters, I would guess that that means that the first two weeks of its life clamped by a Shottkey diode it may be off by as much as 1/8 of an F stop. However, with no diode the 1/3 stop correction for under exposure would come back into play (actually a tad more).

After this early period the silver oxide cell is as flat as mecury's. To me this is not worth worrying about.
 
JeremyLangford said:
Heres this graph I found. But why is Zinc-Air the farthest to the right, making it look like it will last the longest?

4viib5t.jpg
Click to expand...
Zinc air cells will last a long time indeed, running under a constant load. Their shelf life after opening the air holes, however is not so good.
 
for a 625 adapter that drops the voltage, try this chap,
Frans de Gruijter in Nederlands and if he has them ready made they are $19 inc post
and if you are so inclined will sell you the kit to do yourself for $5
can be reached by email to battery.adapter@orange.nl
 
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