Battery type Kodak K — Compatible cameras

The Kodak K is a 4.5-volt alkaline battery developed from the early 1970s specifically for compact 110 film cameras. It is identical to the Eveready 538 and Mallory 7K31 (also 7R31, RPX31) 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 associated cameras are electronically designed for this and are not voltage-critical. It has not been manufactured since the late 1990s.

The Kodak K was used in a whole generation of compact 110 film pocket cameras from the 1970s and 1980s — typically where the electronic shutter or flash readiness required power, but the film advance was manual via a slide 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 as well as XR308

Note: Purely mechanical 110 cameras like the Pocket Instamatic 20 with Magicube connection work completely without batteries. Some Ektra models with built-in electronic flash use AA batteries instead of the Kodak K — if in doubt, check the manual briefly. The full compatibility list can be found 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, the reason was not an environmental ban but simply the disappearance of the market. Occasional NOS stocks still appear at collector fairs but are expensive and often already discharged due to age.

Since the original battery was already an alkaline cell, the replacement is technically uncritical — the key is the correct voltage of 4.5 V and the matching size. Common options:

• Adapter with 3 × LR44 (standard button cells): Three LR44 alkaline cells connected in series provide exactly 4.5 V. Available from Ausgeknipst as a reusable Kodak K replacement adapter made of PLA+ — screwable, button cells can be replaced individually. LR44 batteries are available everywhere in drugstores.
• 3 × SR44 (silver oxide) instead of LR44: Same size, a bit more expensive, but more stable voltage and longer runtime. Not a mandatory upgrade for Kodak K use, but technically cleaner.
• NOS original battery: Occasionally offered on eBay as old stock. Risk: self-discharge over the decades — fresh LR44 batteries are usually the more reliable choice.