Kodak K Battery: Compatible Cameras

The Kodak K is a 4.5-volt alkaline battery developed from the early 1970s onwards specifically for compact 110 film cameras. It’s the same battery sold as the Eveready 538 and Mallory 7K31 (also 7R31, RPX31), and inside it consists of three 1.5 V cells wired in series. Unlike the mercury PX625, the Kodak K has a typical alkaline discharge curve. The cameras that use it were designed electronically with this in mind and aren’t sensitive to voltage. It hasn’t been manufactured since the late 1990s.

The Kodak K powered a whole generation of compact 110 pocket cameras from the 1970s and 1980s, typically models that needed power for the electronic shutter or to get the flash ready, while the film was still advanced by hand 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: Purely mechanical 110 cameras such as the Pocket Instamatic 20 with its Magicube socket work without any battery at all. Some Ektra models with a built-in electronic flash use AA batteries instead of the Kodak K, so if in doubt, take a quick look at the manual. You’ll find the full compatibility list at the top of this page.

With the decline of the 110 format and the Pocket Instamatic family in the late 1990s, Energizer and every other major manufacturer dropped the Kodak K from their ranges. It’s listed as obsolete, but unlike the PX625, the reason wasn’t an environmental ban. The market simply disappeared. The odd batch of NOS (new old stock) still turns up at collectors’ fairs, but it’s expensive and, given its age, often already drained.

Since the original was already an alkaline battery, replacing it is technically straightforward. All that matters is the correct voltage of 4.5 V and the right size and shape. The usual options:

• Adapter with 3 × LR44 (standard button cells): Three LR44 alkaline cells in series give you exactly 4.5 V. At Ausgeknipst, you’ll find this as a reusable Kodak K replacement adapter made from engineering plastic, with a screw-together housing and button cells you can swap individually. LR44s are available at any drugstore.
• 3 × SR44 (silver oxide) instead of LR44: Same size and shape, a little more expensive, but with a steadier voltage and longer life. Not a must-have upgrade for Kodak K cameras, but the technically cleaner solution.
• Original NOS battery: Occasionally offered on eBay as old stock. The risk is self-discharge over the decades, so fresh LR44s are usually the more reliable choice.