Battery Question

[dynachrome]

I have had a number of Canon and Minolts film cameras converted to 1.5 volts. They work properly with 625A batteries but those batteries don't last that long. Does anyone make a silver oxide 625 battery?

 

[MattKing]

No.
Although you might be able to use one of those mechanical adapters sized for zinc air batteries, and put an equivalent sized silver oxide cel in instead.
What sort of conversion do you have that solves the problem of the continuous change of voltage from a 625A battery?

 

[dynachrome]

That's a good question. As I understand it, older cameras had no voltage regulator so they relied on the constant voltage output of mercury batteries. Where PX-13 batteries are concerned, I have used MR-9 adapters with MS76 or 386 1.5 volt batteries. The Canon F-1/F-1n and FT series cameras which have been converted for use with 1.5 volt batteries all work well. The same us true for the converted Minolta SRT cameras. I use 625A batteries in them. I have plain adapters without voltage conversion and with certain cameras I can use 675 zinc-air hearing aid batteries. They don't last terribly long but work. A silver oxide 625 would be nice for some of the converted cameras.

 

[mgb74]

Sometimes, depending on the battery compartment, all you need is a rubber o-ring around a silver oxide battery like a SR44. A #9 o-ring should get you close.

 

[wiltw]

I have had a number of Canon and Minolts film cameras converted to 1.5 volts. They work properly with 625A batteries but those batteries don't last that long. Does anyone make a silver oxide 625 battery?

Just curious in the context of life..do these bodies have power switches, or are they like many mercuric oxide powered units, with no integrated power siwitch?
Do you cover lens with a cap so no light is entering the camera during non-use?
Or is your comment about life in the context of life while in use?

 

[dynachrome]

I have used the o ring method with some cameras. The cameras I mentioned all have meter switches and I try to remember to turn them off when the cameras are not in use. My Pentax Spotmatic F cameras do not have meter switches so I keep caps on the lenses. They run on MS76/A76/357 batteries. My Spotmatic and Spomatic IIa cameras take RM400R batteries but they have meter switches.

 

[wiltw]

I have used the o ring method with some cameras. The cameras I mentioned all have meter switches and I try to remember to turn them off when the cameras are not in use. My Pentax Spotmatic F cameras do not have meter switches so I keep caps on the lenses. They run on MS76/A76/357 batteries. My Spotmatic and Spomatic IIa cameras take RM400R batteries but they have meter switches.

So it sounds as if all the meter-preserving technique are in use, so when you say 'short life battery' what is that duration?

 

[dynachrome]

There isn't an exact duration. My experience is that MS76 batteries last longer than A76 batteries. This is why I was thinking that a silver oxide version of a 625 battery might last longer than an A625. Maybe I'm just noticing that the silver oxide batteries do better in cold weather.

 

[John Bragg]

Sometimes, depending on the battery compartment, all you need is a rubber o-ring around a silver oxide battery like a SR44. A #9 o-ring should get you close.

+1 Best suggestion.

 

[Chan Tran]

There isn't an exact duration. My experience is that MS76 batteries last longer than A76 batteries. This is why I was thinking that a silver oxide version of a 625 battery might last longer than an A625. Maybe I'm just noticing that the silver oxide batteries do better in cold weather.

I don't think you should worry about it. I don't think you use the camera that often do you? If you do use it that often your film cost makes the battery cost looks like nothing.

 

[wiltw]

There isn't an exact duration. My experience is that MS76 batteries last longer than A76 batteries. This is why I was thinking that a silver oxide version of a 625 battery might last longer than an A625. Maybe I'm just noticing that the silver oxide batteries do better in cold weather.

your perception of longer relative life of silver oxide is verifiable. In the context of button cells...

"1) Silver oxide batteries have a 50% - 100% greater capacity, meaning they last up to twice as long as alkaline batteries.
2) Silver oxide has a relatively slow declining voltage during discharge compared to alkaline, which is preferable for light meters used in cameras and digital calipers."​

 

[dynachrome]

An overhauled Canon FTb arrived today. It had been converted for use with 1.5 volt batteries. The 625A batteries I have on hand are all dead as door nails. I put a smaller but fresh MS76 battery in the center of the battery chamber and screwed on the cap. The meter is now working properly. Fresh 625As are on the way.

 

[MattKing]

Fresh 625As are on the way.

What conversion have you had done that modifies the inconsistent voltage from a partially exhausted alkaline battery?

 

[wiltw]

your perception of longer relative life of silver oxide is verifiable. In the context of button cells...

"1) Silver oxide batteries have a 50% - 100% greater capacity, meaning they last up to twice as long as alkaline batteries.
2) Silver oxide has a relatively slow declining voltage during discharge compared to alkaline, which is preferable for light meters used in cameras and digital calipers."​

If you also consider the actual output Voltage of alkaline continuously drops, only a fraction of its life is it able to output more than the 1.35V (red line) that a diode would 'regulate' it down to

In comparison, silver oxide would stay above the red line considerably longer!

 

[dynachrome]

I haven't done the modification myself so I would have to ask the repairmen to describe them. My guess is that even with cameras which were made to work with 1.5 volt batteries, some kind of voltage regulation was taking place and that the batteries would continue to work until voltage dropped below a certain level. The early cameras using 1.5 volt batteries had CdS meter cells. Later cameras had SBC, GPD and other cell types and may have different voltage needs.

 

[Chan Tran]

If you also consider the actual output Voltage of alkaline continuously drops, only a fraction of its life is it able to output more than the 1.35V (red line) that a diode would 'regulate' it down to

In comparison, silver oxide would stay above the red line considerably longer!

Also if you regulate the voltage by having a zener diode in parallel you would waste too much power. If you do it by having a diode in series then you have the assume that the battery voltage is constant and is higher than 1.35V that you want. In either case I don't think that solution would work too well.

 

[MattKing]

The early cameras using 1.5 volt batteries had CdS meter cells.

I think that you will find that the early cameras with CdS cells used 1.35 volt mercury batteries.

 

[wiltw]

I think that you will find that the early cameras with CdS cells used 1.35 volt mercury batteries.

True.
When I get a chance, I will have to look in OM-2n documentation to see which battery, as it had the Silicon Blue photocells rather than CdS.
Yup, OM-2 used SR44/LR44 button cells (silver, alkaline)

 

[mgb74]

True.
When I get a chance, I will have to look in OM-2n documentation to see which battery, as it had the Silicon Blue photocells rather than CdS.
Yup, OM-2 used SR44/LR44 button cells (silver, alkaline)

Though I do remember reading that some had issues with the alkaline LR44 in the OM-2n. And switching to silver oxide resolved the issue.

 

[MattKing]

In the instruction manual for the OM-2, it says:

In the instruction manual for the OM-2n, it says:

In Contrast, in the instruction manual for the OM-2s, it says:
Power Source: Tow (sic) 1.5V silver-oxide batteries SR44 (Eveready EPX-76) or
alkaline manganese batteries LR44

The instruction manuals for the OM-G (OM-20) and the OM-4T are similar to the OM-2s, in that they prescribe both silver oxide and alkaline batteries.

 

[grat]

What conversion have you had done that modifies the inconsistent voltage from a partially exhausted alkaline battery?

With my analog spot meter, when the meter starts drifting downwards while taking a reading, I need a new battery.

The early cameras using 1.5 volt batteries had CdS meter cells. Later cameras had SBC, GPD and other cell types and may have different voltage needs.

I think that you will find that the early cameras with CdS cells used 1.35 volt mercury batteries.

Yes, but I think you'll find that the early cameras that used 1.5v batteries-- used 1.5v batteries. And CdS cells.

 

[mshchem]

All this talk, calling a cell a battery......even the manufacturer! Ha!!!

 

[reddesert]

The issue with that battery drain chart - it's measuring battery voltage at a current draw of 45 milliamps (1.5 V / 33.2 ohms load). No camera meter or shutter from the button-battery era draws that kind of current. I found a repair manual that says the current draw of a Nikon F3 with meter and LCD is 5 milliamps.It would be even lower for a camera without an LCD such as an OM-2, maybe more like 1 milliamp. Of course the chart is intended to measure the voltage curve quickly rather than waiting a month to get a result, but it gives an unrealistic picture of battery discharge in actual use. It's killing the battery by overloading it.

In actual use, people do put alkaline batteries in cameras and the world doesn't come to an end; maybe they sacrifice accuracy at the slide-film 1/3-stop level.

 

[wiltw]

The issue with that battery drain chart - it's measuring battery voltage at a current draw of 45 milliamps (1.5 V / 33.2 ohms load). No camera meter or shutter from the button-battery era draws that kind of current. I found a repair manual that says the current draw of a Nikon F3 with meter and LCD is 5 milliamps.It would be even lower for a camera without an LCD such as an OM-2, maybe more like 1 milliamp. Of course the chart is intended to measure the voltage curve quickly rather than waiting a month to get a result, but it gives an unrealistic picture of battery discharge in actual use. It's killing the battery by overloading it.

In actual use, people do put alkaline batteries in cameras and the world doesn't come to an end; maybe they sacrifice accuracy at the slide-film 1/3-stop level.

Yes, that chart shows it is drain on AA battery. There are no similar graphs for alkaline button cells, not that I could find. The point was constant voltage drop, although it might not be as severe a slope when drain as not as high.

 

[wiltw]

Yes, that chart shows it is drain on AA battery. There are no similar graphs for alkaline button cells, not that I could find. The point was constant voltage drop, although it might not be as severe a slope when drain as not as high.

I finally found a chart for alkaline button cell, in this case an Ansmann 1.5V button. The chart shows that with about 500 hour life (at the drain rate plotted), the 1.5V alkaline button sell is only above 1.35V for 200 hours, or 40% of its life!