Battery type PX24 — Compatible cameras

The PX24 (also Eveready 532, V24PX, A24PX, EPX24, or 2LR50) is a cylindrical 3.0-volt alkaline battery consisting internally of two 1.5-V alkaline cells connected in series. It has two large snap-button contacts (Snap-Connectors) at both ends and measures about 16.8 × 42.4 mm. It was manufactured from the 1960s by Mallory, Eveready, Varta, and Duracell — still available today as a special battery from Exell (A24PX/532). Important: Unlike the better-known PX625 or PX27, the PX24 is not a mercury cell — it has been an alkaline battery from the start and therefore is not subject to the mercury bans of the EU Battery Directive 2006/66/EC.

The PX24 was mainly used in Polaroid Land cameras with pack film from the late 1960s and 1970s. The most important models are listed on this page: Polaroid Colorpack M6, Countdown M60, Countdown M80, and "The Clincher." Many other Polaroid Automatic and Countdown models also use the PX24 — with one battery e.g. Automatic 103, 104, 125, 135, 210, 215, 315, 320, 330, 420, 430, 440 as well as Countdown 70 and M60; with two batteries (one for the shutter, one for the development timer) Automatic 335, 350, 360, 450 as well as Countdown 90 and M80. Important: The similarly named Polaroid Automatic 100, 240, and 250 do NOT require the PX24/532, but the PX19/531 with 4.5 V — this is a common confusion.

Original PX24 batteries are no longer produced by mass manufacturers. However, they are still available in two variants:

• Special New Production (Exell A24PX / 532): The US manufacturer Exell Battery still produces the original design today as an alkaline battery. Available through photo specialists and online retailers, but usually at a significantly higher price than standard batteries.
• Battery adapter with standard button cells: An adapter in the PX24 format that internally holds two common 1.5-V button cells (LR44/SR44) and has the correct push-button contacts. Advantage: cheap, permanently available, standard batteries available everywhere. Available from Ausgeknipst as PX24/532 Adapter 3V.

There are several options for the PX24 — each with its own strengths and weaknesses:

• Exell A24PX (original form factor): Direct replacement in original format, alkaline chemistry, 3.0 V. Plug-and-play without adapter, but relatively expensive and rarer in stores. Disadvantage like any alkaline battery: the voltage continuously drops during discharge.
• PX24 adapter with 2x LR44 (alkaline): Cheap, standard batteries available everywhere, nominally 3.0 V. Disadvantage: continuously dropping voltage; as soon as the cells get tired, the reading fluctuates.
• PX24 adapter with 2x SR44 (silver oxide): Higher capacity than LR44, significantly more stable discharge curve, nominally 3.1 V. Slightly more expensive than LR44, but clearly the better choice for the exposure meter because the voltage remains constant over almost the entire lifetime.
• 3-V lithium cell (CR type) in adapter: Very long shelf life (~10 years), exactly 3.0 V, extremely flat voltage curve. Disadvantage: form factor fits only in special adapters and not every Polaroid Land has enough space for a larger CR cell.

In Polaroid Land cameras with electronic exposure automation, a higher voltage than the specified 3.0 V causes the CdS exposure meter to accept more light and open the shutter for a shorter time — resulting in slight underexposure. Conversely, too low a voltage leads to overexposure. However, the exposure electronics of packfilm Land cameras are relatively tolerant: fluctuations between 3.0 V (2x LR44) and 3.1 V (2x SR44) usually remain within the film tolerance in practice. Polaroid packfilm, like color negative film, forgives overexposure better than underexposure, so slight undervoltage is generally the lesser evil.

Even more important than the absolute voltage value is the consistency over the discharge curve: alkaline cells (including the original PX24) continuously lose voltage and deliver fluctuating readings over their lifetime. Silver oxide (2x SR44) keeps the voltage stable over almost the entire discharge and is therefore the technically cleanest choice for any older camera with exposure automation — regardless of whether the original was a Hg or alkaline cell.