View Full Version : 35 RC / RD / SP battery drain

01-30-2009, 11:09
does anyone know how long an original (mercury) battery actually lasts in these cameras?

The RC you can put in an 'off' position, but still I found that the battery went dead after a while.

With the RD the light meter appears to be switched off when not in 'A' mode. So setting the camera on anything else should be the same as the 'off' with the RC and save the battery, just that the shutter can still be released. Is this correct?

And with the SP, how much battery drain does actually take place when the camera is put into its case so that the cell is in the dark? Did anyone ever check?


01-30-2009, 11:34
I use an alkaline 625 in my SP; the camera was adjusted for the higher voltage.

The autoexposure is the only application of the battery. In typical cameras of the period, the resistance of the CdS sensor circuit goes from about 5 kOhm (illuminated) to about 50 Kohm or higher (dark). So current drain should be around 0.3 mA to 0.03 mA - that is a very small drain. In any case think less than 1 mA if you want to compute battery duration conservatively.

At the beginning I was very concerned that the 35 SP camera did not have an "off" switch. But now I have used the camera for whole days, several hours without covering the sensor, in strong sunlight -- the autoexposure of the 35 SP is still working well, with the same 625 battery after more than maybe 20 rolls and two years of use.

I do carry an extra battery when the 35SP is the only camera at hand, just for comfort.

01-31-2009, 03:34
Let me add that a typical 625 alkaline such as the Varta 625 has 200 mAh capacity, which would give you theoretically 600 hours of shooting with the sensor pointed to a light source.