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Button alkaline (LR / AG)

LR9 (PX625A) battery: equivalents & specs

The LR9, better known as the PX625A or V625U, is a 1.5 volt alkaline button cell, 15.6 mm across and 6.2 mm tall. It is the modern stand-in for the discontinued 1.35 volt PX625 mercury cell that powered light meters in classic cameras.

LR9 (PX625A) battery drawing: 15.6 mm across, 6.2 mm thick LR9 1.5V + ⌀ 15.6 mm 6.2 mm
LR9 (PX625A), face and side profile, drawn to scale: 15.6 mm across, 6.2 mm thick.
Voltage
1.5 V
Size (D×H)
15.6 × 6.2 mm
Chemistry
Alkaline (Zn/MnO2)
Capacity
150-200 mAh

Same battery, other names

Every code below is the exact same cell as LR9 (PX625A). Any of them will fit and work identically.

PX625AV625U625AEPX625G

⚠️ Vintage meters calibrated for 1.35 V mercury cells will read incorrectly on this 1.5 V cell unless the camera has a bridge-type meter circuit or you use an adapter.

Buying and replacement notes

The catch with this cell is voltage, not fit. The original mercury PX625 delivered a very stable 1.35 V, and many vintage camera meters (Canonet, Olympus OM-1, various Rolleis) were calibrated for exactly that. A 1.5 V LR9 fits the chamber but reads about one stop off, and the error shifts as the cell discharges. Fixes include an MR-9 adapter with a voltage-dropping diode, a zinc-air Wein cell at 1.4 V, having the meter recalibrated, or simply compensating with the film speed dial.

Commonly used in

vintage film camerasclassic light metersolder photographic equipment

Need a replacement?

Shop LR9 (PX625A) batteries on Amazon →

⚠️ Keep away from children. Swallowed button batteries, especially 20 mm lithium coins, cause severe injury within hours. If a child swallows one, call the 24/7 National Battery Ingestion Hotline (US) at 800-498-8666 or poison control at 800-222-1222 immediately. What every parent should know.

Frequently asked questions

Can the LR9 directly replace a PX625 mercury battery?
It fits the same compartment, but it outputs 1.5 V where the mercury cell gave 1.35 V. Cameras with voltage-dependent meters will overread by roughly one stop. Use an MR-9 adapter, a Wein zinc-air cell, or recalibration if accurate metering matters to you.
What is a Wein cell?
A zinc-air battery built in the PX625 shape that outputs about 1.4 V, close enough to the original mercury voltage for most meters. It activates when you peel its seal and then lasts only a few months whether used or not, so buy one when you plan to shoot.
My old camera works fine on the LR9. Why?
Some cameras, and most later ones, use bridge circuits that compare resistances rather than measuring absolute voltage, so they meter correctly across a range of battery voltages. Check your model's documentation; if it has a bridge meter, the 1.5 V LR9 is a clean, cheap replacement.

More Button alkaline (LR / AG) cells

LR44LR43LR1130LR41LR626LR621LR521LR726LR721LR754