Index / Shells / 7.9 x 5.4 mm

7.9 x 5.4 mm

4 designations carry this exact envelope and they disagree on voltage: MR48 runs 1.4 V where SR48 runs 1.55 V, 9.7% apart. The compartment cannot tell them apart and the circuit can. Capacity is where they part: 193 holds 53 mAh and MR48 holds 100, 1.9 times as much. This envelope has no household name, so the code on the cell is the only handle on it.

Also stamped on cells in this table: PR48, 7000ZD, AC13E, SR48, 1136SO, 309, 1137SO, 393, 1181SO, S13E, 193, MR48, 1156M, 323.

The published figures agree

This page is collected by envelope, so the 4 designations here share 7.9 x 5.4 mm by construction. What is worth checking is that the maker publishes the same pair for each of them, and here it does: the records behind all 4 agree as printed, so nothing on this page rests on a figure one record disputes.

One envelope, 4 different voltages

A compartment marked 7.9 x 5.4 mm takes any of them, and that is the whole difficulty: the fit says nothing about the electrics. Between the lowest and the highest here the difference is 1.4 V against 1.55 V, or 9.7% of the nominal figure.

• 1.55 V — 1 designation: SR48
• 1.5 V — 1 designation: 193
• 1.45 V — 1 designation: PR48
• 1.4 V — 1 designation: MR48

What that costs depends on what the device does with the figure rather than on the figure itself. A motor or a lamp runs slower and dimmer and comes to no harm. A meter, a scale or a thermometer reads the cell as part of its own reference and reports a number that is wrong by about the same 9.7. A circuit with a regulator either holds its output or cuts out early, and which of them it does is not printed on the case. This site never answers that question for a device it cannot see; it gives the figure and names the class of consequence.

How much energy is actually in there

Milliamp-hours cannot be compared across chemistries. A milliamp-hour at 1.55 V carries more energy than a milliamp-hour at 1.4 V, and the capacity column hides that. Multiplying the published capacity by the published voltage puts every designation called 7.9 x 5.4 mm on one scale, and on that scale the range is 1.8 times wide — MR48 carries about 140 mWh and 193 about 80 mWh.

• MR48 — 140 mWh (100 mAh at 1.4 V)
• SR48 — 116 mWh (75 mAh at 1.55 V)
• 193 — 80 mWh (53 mAh at 1.5 V)

These are the maker's own figures at the maker's own test load, and a cell asked for more current than that test uses delivers less. The number is a ceiling and a way to compare, not a promise of runtime in a particular device.

The compartment takes any of them; the circuit does not

4 kinds of chemistry are sold as 7.9 x 5.4 mm in this data, and the difference between them is not a difference of size. A holder marked 7.9 x 5.4 mm closes on all of them, so nothing about the fit warns anybody which one the device was designed around. What follows is what each kind does that the millimeters do not say.

• Zinc air (1 designation here) 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.
• Silver oxide (1 designation here) holds its voltage almost flat until it is spent, which is why watches and light meters were built around it.
• Alkaline (1 designation here) drops in voltage steadily as it empties, so a device calibrated for a flat discharge will drift as it goes.
• Mercuric oxide (1 designation here) held a very flat 1.4 V, which is what old meters were calibrated against. The chemistry is banned for consumer sale in the United States and the European Union, and this site reads one maker's catalog, so what still reproduces that voltage is a question it cannot answer.

None of this is a recommendation for a particular device. The device decides: a lamp tolerates almost anything that fits, a meter reports a number that is wrong by whatever the voltage is wrong by, and a sealed compartment is the one case where a zinc-air cell cannot work at all however well it sits. Where the maker of the equipment names a chemistry, that naming outranks every figure on this page.

What stands next to this envelope in the data

The envelope above is not the only one near it. Cells that miss by a fraction of a millimeter sit in the same drawer and look identical in the hand, and the question they raise is the one this site answers: not whether a cell is the same, but what the difference does. These are the nearest envelopes to 7.9 x 5.4 mm in this data, closest first.

• 7.8 x 5.3 mm — drops straight in, first met here as NR48.
• 7.9 x 3.7 mm — fits but sits lower, first met here as MR41.
• 7.9 x 3.6 mm — fits but sits lower, first met here as LR41.
• 7.9 x 3.1 mm — fits but sits lower, first met here as 329.
• 7.9 x 2.6 mm — fits but sits lower, first met here as SR59.
• 8.9 x 3.3 mm — is too wide to enter, first met here as 1157M.

Of the nearest 6, 1 would drop straight in on size. Every verdict in that list is about the compartment alone. A cell that drops in physically can still be the wrong cell: the voltage and the chemistry are separate questions, answered separately above and on the page of each designation. Nothing here says a substitution is safe for a particular device, and where the maker of the device names a cell, that naming outranks every millimeter on this page.

What is gone from this shell

2 designations of the 4 here are no longer listed by Energizer: 193 and MR48. The table below measures each still-listed cell against 193; the others carry their own figures on their own pages.

Fit answers whether it enters the compartment; every cell here shares the envelope, so fit is already settled. Voltage answers whether the circuit will notice, and chemistry answers what the voltage column cannot say. A cell that fits is not always a safe substitute.

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.

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.