PX24 Battery: Compatible Cameras

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

The PX24 was mainly used in Polaroid Land pack film cameras from the late 1960s and 1970s. The Automatic 103, 104, 125, 135, 210, 215, 315, 320, 330, 420, 430 and 440 as well as the Countdown 70 and M60 run on one battery. The Automatic 335, 350, 360 and 450 as well as the Countdown 90 and M80 need two batteries (one for the shutter, one for the development timer). The Colorpack M6 and "The Clincher" also take the PX24. All models are listed in the table above. Important: The similar-sounding Polaroid Automatic 100, 101, 102, 220, 225, 230, 240, 250, 340 and 355 do NOT take the PX24/532 but the PX19/531 with 4.5 V. This is a common mix-up.

Original PX24 batteries are no longer produced by the 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 form factor today as an alkaline battery. Available from photo specialists and online retailers, though usually at a considerably higher price than standard batteries.
• Battery adapter with standard button cells: An adapter in the PX24 format that holds two commercially available 1,5 V button cells (LR44/SR44) inside and has the correct snap contacts. Advantage: inexpensive, always available to reorder, standard batteries available everywhere. Available at Ausgeknipst as PX24/532 Adapter 3V.

There are several routes open for the PX24, each with its own strengths and weaknesses:

• Exell A24PX (original form factor): Direct replacement in the original format, alkaline chemistry, 3,0 V. Plug and play without an adapter, but relatively expensive and harder to find in stores. Drawback, as with any alkaline battery: the voltage drops continuously as it discharges.
• PX24 adapter with 2x LR44 (alkaline): Inexpensive, standard batteries available everywhere, gives a nominal 3,0 V. Drawback: continuously dropping voltage; as soon as the cells get tired, the meter reading fluctuates.
• PX24 adapter with 2x SR44 (silver oxide): Higher capacity than LR44, much more stable discharge curve, gives a nominal 3,1 V. Slightly more expensive than LR44, but clearly the better choice for the light meter, because the voltage remains constant over almost the entire service life.
• 3 V lithium cell (CR type) in an adapter: Very long shelf life (~10 years), exactly 3,0 V, extremely flat voltage curve. Drawback: the form factor only fits special adapters, and not every Polaroid Land has enough room for a larger CR cell.

In Polaroid Land cameras with electronic automatic exposure, a voltage higher than the nominal 3,0 V causes the CdS light meter to assume more light and open the shutter for a shorter time. This results in slight underexposure. Conversely, a voltage that is too low leads to overexposure. However, the exposure electronics of the pack film Land cameras are relatively tolerant: variations between 3,0 V (2x LR44) and 3,1 V (2x SR44) usually stay within the film's latitude in practice. Like color negative film, Polaroid pack film forgives overexposure better than underexposure, so a slight undervoltage tends to be the lesser evil.

Even more important than the absolute voltage value, however, is consistency across the discharge curve: alkaline cells (including the original PX24) lose voltage continuously and deliver fluctuating readings over their service life. 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 automatic exposure, regardless of whether the original was an Hg or alkaline cell.