TYPE 640 Mercury Battery Adapter

Save your vintage equipment from the trash! 
Replace the Type 640 Mercury Battery with an environmentally friendly Zinc-Air Battery

Click here to purchase:

$35 shipped anywhere in the USA via USPS Priority Mail

The Type 640 battery is no longer available - it is a mercury battery and improper disposal is bad for the environment. The currently marketed replacement battery of the same type number is an alkaline type. It has a different voltage and discharge curve, which would make devices such as camera meters inaccurate if used as a replacement.

I did a bit of research and discovered that zinc-air batteries are the same voltage, AND similar discharge curve. They are available at Radio Shack, and cheap. So, I designed and built an adapter to use the Type 675 zinc-air battery ($12 for 16 of them at RS!), in place of the evil Type 640. It works great!!

I loathe retiring good equipment due to battery obsolescence. This adaptor saved a perfectly functional Honeywell Pentax spotmeter from being relegated to the scrap heap.

The adaptor is CNC machined from high-quality Type 360 Brass. These adaptors are very popular, and are made in batches. Please allow 3-4 weeks for delivery. One zinc-air battery is included.

NOTES:

1)  This adapter was designed specifically to replace a Type 640 Mercury battery only.  It will not work for other types.  While it is possible that other types of mercury batteries can be similarly accommodated, a new design would be required.

2)  Kindly refrain from sending me emails as to whether this adapter will work for a particular camera or light meter.  I have no idea if any particular equipment had used the type of mercury battery that this adapter addresses, save one: the Honeywell Pentax Spotmeter, as pictured above.

3)  This adapter will work for any application where a Type 640 was used, but is best for a low-current application such as a light meter.  You may research the characteristics of the zinc-air battery at Duracell's excellent site.

4)  The zinc-air batteries have a higher self-discharge rate than the mercury batteries did.  You may have to replace your light meter batteries after a month, instead of after a year with the mercury batteries.  But, they cost less than a dollar each, and more importantly they are available at Radio Shack!

Last updated: 28 July 2006 20:52

If you have questions, please email me at spencer313@yahoo.com.

Thank you!