Battery type Kodak K: Compatible cameras

The Kodak K is a 4.5-volt alkaline battery developed specifically for compact 110-film cameras from the early 1970s onward. It is identical in design to the Eveready 538 and Mallory 7K31 (also 7R31, RPX31) designations and internally consists of three 1.5 V cells connected in series. Unlike the mercury PX625, the Kodak K has a typical alkaline discharge curve. The corresponding cameras are electronically designed for it and are not voltage-sensitive. It has not been manufactured since the late 1990s.

The Kodak K was used in an entire generation of compact 110-film pocket cameras from the 1970s and 1980s, typically where the electronic shutter or flash readiness required power, while film advance was operated manually with a sliding lever. Common models:

• Kodak Pocket Instamatic 30, 40, 50, 60 (electronic shutter)
• Kodak Trimlite 28, 38, 48 and Tele-Instamatic 708
• Kodak Ektramax
• Kalimar K-90 and Kalimar Micro 110
• Keystone Pocketmatic 101 to 105 and XR308

Note: Fully mechanical 110 cameras such as the Pocket Instamatic 20 with a Magicube connection work without a battery. Some Ektra models with a built-in electronic flash use AA batteries instead of a Kodak K; if in doubt, briefly check the instruction manual. You can find the complete compatibility list at the top of this page.

With the decline of the 110 film format and the Pocket Instamatic family in the late 1990s, the Kodak K was discontinued by Energizer and all major manufacturers. It is listed as obsolete; unlike the PX625, this was not due to an environmental ban but simply because the market disappeared. Occasional NOS stocks still turn up at collectors' fairs, but they are expensive and, due to their age, often already discharged.

Since the original battery was already an alkaline cell, the replacement is technically unproblematic; what matters is the correct voltage of 4.5 V and the appropriate size. Common options:

• Adapter with 3 × LR44 (standard button cells): Three LR44 alkaline cells connected in series provide exactly 4.5 V. At Ausgeknipst, they are available as a reusable Kodak K replacement adapter made of technical plastic, secured with screws; the button cells can be replaced individually. LR44 batteries are available everywhere at drugstores.
• 3 × SR44 (silver oxide) instead of LR44: Identical size, slightly more expensive, but with a more consistent voltage and longer runtime. Not a required upgrade for the Kodak K application, but technically the better option.
• NOS original battery: Occasionally offered on eBay as old stock. Risk: self-discharge over the decades; fresh LR44 batteries are generally the more reliable choice.