Zinc Air 675 Battery

[Andrew O'Neill]

I bought a pack for a few of the older cameras that used to take mercury cells. I see that they are 1.4V, and the proper battery for the K1000 is 1.5....So, I thought I'd stick one in. Metre works fine, compared to proper battery. Is this a bad idea? Any long term effects? Shorter life span? If not, I really would like to use the 675's for all the K1000's. Very economical, and for high school, that's a bonus! Cheers!

 

[Chan Tran]

The only effect is the meter may read wrong. If you don't have the problem then there is nothing to worry about. It wouldn't hurt the camera. Come to think of it, it's difficult to design a circuit that works perfectly well on 1.4V and got damage with 1.5V.

 

[Andrew O'Neill]

Thanks Chan Tran. I'll see how it goes...

 

[Paul Howell]

I use hearing aid batteries in a number of old cameras, Miranda, Konica, Petri, Canon QL 1.7, ect, seems to work in all within a stop of my hand held meter.

 

[Andrew O'Neill]

Interesting. Thank you, Paul. I'll have to run some film through the Pentax and see what happens. Cheers!

 

[jim10219]

Zinc air will work fine. They have a really steady discharge curve, unlike an alkaline battery. The alkaline battery has a bit more voltage to begin with. But at the halfway point in these two batteries (alkaline and zinc air) lifecycles, they should be running around the same voltage (around 1.2-1.3v). On the second half of their life cycles, the zinc air will have more voltage. So in reality, they should operate very similarly over the course of their lifespan.

Also, the K1000 meter runs on a modified Wheatstone bridge circuit, like the Spotmatic F. Therefore, the meter circuit is very tolerant of higher and lower voltages, so the voltage change shouldn't effect the meter's accuracy. So this particular camera shouldn't have any issues.

 

[Andrew O'Neill]

Fantastic! Thank you for sharing that, Jim! Cheers!

 

[cooltouch]

Jim makes a good point. The 675's discharge profile is almost exactly the same as the original mercury battery's discharge profile -- which is great news for folks with the old cameras that take the mercury batteries. True, the zinc-airs don't last all that long, but they're so cheap, who cares? I buy a card of 48 of them at Costco for less than $10.

One thing that is true about most Pentaxes that I've read is that they have a bridge circuit, which means they are insensitive to battery voltage. The bridge circuit dates back to the Spotmatics and is also part of the K1000's meter circuitry.