Description
The GP PX625A, often cross-referenced as LR9 or V625U, is a 1.5-volt alkaline zinc-air button cell battery designed as a modern, mercury-free replacement for the original, now-obsolete PX625 mercury battery. Its most notable application is in vintage cameras and light meters from the mid-20th century, such as those by Pentax, Leica, and Olympus, which relied on the stable 1.35-volt discharge of mercury cells. This voltage discrepancy is the core issue: while physically identical, the alkaline cell’s 1.5V output can lead to overexposure if not corrected. To address this, users often employ voltage-reducing adapters or opt for specialized 1.35V zinc-air replacements (like the Wein cell) or silver oxide cells with built-in voltage regulation. Thus, the GP PX625A/LR9/V625U remains a readily available and affordable stopgap solution, but its use requires careful consideration of the device’s voltage sensitivity to ensure accurate operation.






