PR43

PR43 — zinc air, 1.4 V, 11.6 x 4.2 mm. Not listed by Energizer, and what still fits does not match the circuit: LR43 drops straight in, and runs 1.5 V — +7.1%, which reads high.

Warning — button cell

PR43 is a button cell: 11.6 mm across and 4.2 mm tall. United States law defines that class by the shape alone — a single cell battery with a diameter greater than its height, 16 CFR 1263.2 — and not by what is inside it. Swallowed, a cell this shape can lodge instead of passing, and it is the current, not the metal, that does the damage. If one has been swallowed, or put in a nose or an ear, call the United States national Poison Help line at 1-800-222-1222 straight away and do not wait for symptoms.

At 11.6 mm and 1.4 V it is under the 16 mm diameter that lodges most readily — which makes it easier to swallow, not safer. The same current runs for as long as it sits.
Zinc air is the one exception, and it is written into the rule: 16 CFR 1263.1(d) records the Commission's determination that zinc-air button cells do not present an ingestion hazard, so part 1263 does not cover this cell. The determination is about the burn. A swallowed object is still a swallowed object, and this one lives in the drawer where the pills are.
The same rule says what to do with the used cell, in its own words: dispose of it at once, keep it away from children, and do NOT put it in household trash (16 CFR 1263.4(b)(3)). Tape over both faces first — a cell too flat to run a watch still has enough left to burn.

What fits the compartment, and what does not

Fit answers whether it enters the compartment. Voltage answers whether the circuit will notice. A cell that fits is not always a safe substitute.

Cell	Fit	Voltage	Chemistry	Capacity
LR43	drop-in	1.5 V +7.1%reads off	alkaline	113 mAh
SR43	drop-in	1.55 V +10.7%reads off	silver oxide	110 mAh
LR54	sits lower	1.5 V +7.1%reads off	alkaline	66 mAh
SR42	sits lower	1.55 V +10.7%reads off	silver oxide	100 mAh
SR54	sits lower	1.55 V +10.7%reads off	silver oxide	85 mAh
SR55	sits lower	1.55 V +10.7%reads off	silver oxide	55 mAh
PR44	too tall	1.45 V +3.6%close enough	zinc air	—
LR44	too tall	1.5 V +7.1%reads off	alkaline	150 mAh
SR44	too tall	1.55 V +10.7%reads off	silver oxide	195 mAh
CR11108	too tall	3 V +114%wrong class	lithium	160 mAh

2 cells drop in and they are not equivalent: of those, SR43 sits furthest at +10.7% of this cell’s 1.4 V, high enough that a calibrated instrument reads above true.

Also stamped 7001Z, AC41E

Nominal1.4V

Diameter11.6mm

Height4.2mm

In the Energizer catalogNot listed

How far each cell that enters this compartment sits from this one’s 1.4 V

−100%, no volts at allthis cell+1000%, 10 times over

The axis is the difference from this cell, not a range of volts: the centre is 1.4 V and the ruled middle is the class where a substitute still runs and only reads off — a gap within 20.0% of the higher of the two nominals, which counted from this cell reaches 20.0% below and 25.0% above. One gap, two readings: the other cell’s page prints the other figure for this same pair and lands on the same class. Outside those two rules the class changes. The middle is drawn straight and the outer fifth of each side is compressed, so the +7.1% mark and the +10.7% mark on this track cannot land in the same place.

Unlisted, and what fits runs at the wrong volts

Energizer no longer lists PR43 (also 7001Z), and what fits the compartment does not match the circuit: LR43 drops straight in but runs 7.1% off, high enough that a calibrated instrument reads above true. In a meter or a camera calibrated for this cell, that shows up as a reading, not as a failure.

What the chemistry changes

Everything above answers size and voltage. What it cannot answer is chemistry, and 2 other kinds are in play here beside the zinc air this cell uses.

Zinc air takes oxygen from the air through the holes in its face. It starts discharging the moment the tab comes off and runs down in weeks whether the device is used or not, and a sealed compartment starves it.
Alkaline drops in voltage steadily as it empties, so a device calibrated for a flat discharge will drift as it goes.
Silver oxide holds its voltage almost flat until it is spent, which is why watches and light meters were built around it.

From BatteryCrossEvery designation in one pageEach code with what it measures and what it replaces

A cell that starts working when the tab comes off

Zinc air takes its oxygen from the room. The sealed tab on the face is what keeps the cell asleep, and pulling it starts the clock whether the aid is switched on or not. No capacity figure is published for PR43, so how long it lasts after the tab comes off is not a number this catalog gives.

A sealed compartment starves it. LR43, MR43 and NR43 in this envelope do not need air, which is why PR43 is the wrong swap into a watch case that closes on a gasket. Nominal 1.4 V, which is below every alkaline and silver oxide cell of this envelope and is what the aid's amplifier is tuned to. The nearest is LR43: it drops straight in and runs 1.5 V, reads off.

Hearing aids are medical devices. Their manufacturers name the cell on the case and in the manual, and that name wins over any table, including this one.
10 cells measure close enough to compare against it in the Energizer data this site reads, and 10 of them are still listed.
Energizer files it for North America, which is where the part is sold rather than where the cell will work.
Energizer no longer lists PR43 at all, so whatever goes into that compartment next will be a substitution rather than a replacement.

Drawn to scale

PR43, side elevation, from the published figures

The same scale for all of them. The dashed line marks the height of PR43: a silhouette that stops short of it will not reach the contact, one that crosses it will not let the cover close.

This cellAnother cell, same scale

Every published figure

Capacity is missing here, and with it every figure derived from capacity: 9 figures are published, 5 fields are not.

Designation	PR43
Also stamped	7001Z, AC41E
Chemistry	Zinc Air
Nominal voltage	1.4 V
Diameter	11.6 mm
Height	4.2 mm
Weight	1.4 g
In the Energizer catalog	No longer listed
Listed for	North America

What the datasheet does not say

Beyond size and voltage the sheet for PR43 is thin: 1 published figure below, and no impedance, no cutoff and no operating range at all. That silence is the maker's, not ours.

Where the part is filed: North America. That is a statement about the maker's distribution and not about where the cell works.

Is that a lot of energy?

Capacity is not published for this cell, so it is absent from the energy ranking rather than placed at the bottom of it. What can be compared is size: 11.6 x 4.2 mm, against a shell that holds 5 designations.

A width the catalog keeps returning to

11.6 mm is a width this catalog keeps coming back to: 20 coins sit within half a millimeter of it, PR43 included.

1177SO — 11.6 x 1.6 mm, 1.55 V, silver oxide.
CR11108 — 11.6 x 10.8 mm, 3 V, lithium.
LR43 — 11.6 x 4.2 mm, 1.5 V, alkaline.
10 of those ones are still listed. 14 of the 82 coins share its 1.4 V exactly.

The maker's own part numbers

PR43 carries 2 names beyond the designation, and every one of them is a manufacturer part number: a catalog line, not a size and not a standard.

7001Z — a manufacturer part number for PR43, not a standard designation.
AC41E — a manufacturer part number for PR43, not a standard designation.

The cell that differs only in depth

The code says the size, so the cells that get confused with PR43 are the ones that keep its diameter and change its depth. 16 cells share this diameter at depths from 1.6 to 10.8 mm, and every one of them enters the same opening.

1177SO — same diameter, 1.6 mm tall against this cell's 4.2: 2.6 mm shallower, which neither designation carries.
365 — same diameter, 1.6 mm tall against this cell's 4.2: 2.6 mm shallower, which neither designation carries.
SR55 — same diameter, 2 mm tall against this cell's 4.2: 2.2 mm shallower, which neither designation carries.
LR43 — the same 11.6 x 4.2 mm in alkaline at 1.5 V. Identical on a caliper, different in the circuit.
MR43 — the same 11.6 x 4.2 mm in mercuric oxide at 1.4 V. Identical on a caliper, different in the circuit.
On a scale the difference shows before it shows on a caliper: this one weighs 1.4 g.

A thin record, and what that costs

The maker's record for PR43 is thin: 5 of 7 fields are blank, and only 2 are filled. What follows from a blank is an absence on this page, never a guess.

The blanks are the same in all 1 record behind this designation, so they are the catalog's silence and not a merge losing a value. What is not missing is the envelope: 11.6 x 4.2 mm, published and checked against the designation itself.

No capacity — so this page cannot tell you how long it runs, and every energy figure that depends on it.
No volume — so this page cannot tell you energy per cubic centimeter, which is how cells of different shapes are compared here.
No cutoff voltage — so this page cannot tell you what the capacity figure was counted down to, without which the capacity is a number without a scale.
No impedance — so this page cannot tell you whether the cell can drive a pulse, which is the whole question in a watch or a sensor.

Before you swap anything

Everything here is computed from published dimensions and nominal voltages. That answers whether a cell enters the compartment and whether the voltage matches on paper. It does not answer what your device does with the difference, and it cannot: a cell that fits can still be the wrong cell.

One more limit, and it is the biggest. This site reads a single manufacturer’s catalog. When a page says a designation is not listed, that means Energizer no longer offers a part under it — not that nobody makes the cell. Other makers may still sell it, and for common sizes they usually do.

A voltage difference is one relation between two cells, and this page prints it from the cell it is about — in every table on the page, including the one listing cells no longer made. A figure always belongs to the cell whose voltage is printed beside it: a cell that runs lower than this one carries a minus here, one that runs higher carries a plus, and two cells at the same nominal voltage carry zero. Meet the same pair on the other cell’s page and the sign is the other one, with the figure taken against that cell instead of this one; where the two run at the same voltage, both pages print zero. The class beside the figure is not read off that figure directly. It is decided on the gap itself, taken against the higher of the two nominal voltages, so one pair of cells gets one class whichever page you meet it on: counted from this side the boundary of the class that still runs falls at 20.0% below and 25.0% above, which is the same gap divided once by the larger nominal and once by the smaller. What genuinely differs between the two directions is the consequence, and the words carry it: a cell that runs low makes a calibrated instrument read below true, and a cell that runs high makes it read above.

3 things this site cannot see. Whether the contacts reach a shorter cell. Whether the device was calibrated for a chemistry that holds its voltage flat, which silver oxide does and alkaline does not. Whether the equipment tolerates the higher current a different chemistry can deliver. Rechargeable cells are never a drop-in for primary cells regardless of size.

Cells measured next to this one

The shell is shared across chemistries: 4 cells sit at exactly this size in alkaline, mercuric oxide and silver oxide. Same hole, different insides, different discharge curve.

LR43 — 11.6 x 4.2 mm, 1.5 V
MR43 — 11.6 x 4.2 mm, 1.4 V
NR43 — 11.6 x 4.2 mm, 1.4 V
SR43 — 11.6 x 4.2 mm, 1.55 V
1177SO — 11.6 x 1.6 mm, 1.55 V
365 — 11.6 x 1.6 mm, 1.55 V
SR55 — 11.6 x 2 mm, 1.55 V
LR55 — 11.6 x 2.1 mm, 1.5 V

Where these numbers come from

Dimensions, voltages, chemistries and capacities are published by the manufacturer and reproduced without change. Everything else on the page is ours, computed from those figures: whether one cell fits where another sat, how far apart their voltages are, stored energy and energy per cubic centimeter, the rank within a shell, and the check of the designation against the measured size.

Fit is decided within 0.3 mm on every axis, which is the order of a contact spring's travel. Voltage classes are decided by consequence, not by roundness, and they are decided on the gap between two nominal voltages taken against the higher of the two: 2.0% or less of it is the same working voltage, 6.0% starts to matter to a calibrated instrument, and past 20.0% it is a different class altogether. Measuring the gap against the higher figure is what makes the verdict the same from either cell’s page, while the printed percentage stays counted from the cell you are reading about. Cells with identical stored energy share a rank instead of being ordered arbitrarily.

Ranking uses capacity times nominal voltage, because capacity alone is not comparable across chemistries: 150 mAh at 3 V is twice the energy of 150 mAh at 1.5 V. Neighbors are chosen by measurement and never alphabetically, because two cells filed next to each other by name usually have nothing in common. A blank in any table means the maker publishes no figure, which is not the same as zero.

Source: Energizer technical data, retrieved 1 September 2026.

The record behind this page

Every figure on this page comes from one catalog record, number 727, and it is linked below. The sheet is the document the dimensions, voltage and capacity were read out of.

[1] Energizer catalog record 727, listed as AC41E, obsolete in the snapshot. Technical data sheet: ac41e.pdf.

Every figure above is reproduced from those records without change; the comparisons are ours and are described on the method page. Snapshot: Energizer technical data, retrieved 1 September 2026.

Putting this on a forum or a repair page? The same answer without the site around it — fit, voltage, chemistry and the limits that go with them — is at /embed/pr43/. It loads nothing from anywhere else. Paste this:

<iframe src="https://batterycross.com/embed/pr43/" width="100%" height="520" loading="lazy" title="PR43 replacements"></iframe>