Index / Shell 10.5 x 44.5 mm / HR03

HR03

HR03 — nickel-metal hydride, 1.2 V, 10.5 x 44.5 mm, known as an AAA cell. Current. LR03 drops straight in, and runs 1.5 V — +25.0%, which reads high; R03 drops straight in, and runs 1.5 V — +25.0%, which reads high.

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.

3 cells drop in and they are not equivalent: of those, LR03 sits furthest at +25.0% of this cell’s 1.2 V, high enough that a calibrated instrument reads above true.

Also stamped 1.2H1, NH12-500MAH, NH12-700MAH, NH12-800MAH, HR03-1000, HR03-850, NH12-600MAH, RE12-500

Same size, and not the same voltage

The AAA compartment takes cells of more than one voltage. This one is 1.2 V; FR03 in the same size runs 1.5 V, +25.0% of this cell — high enough that a calibrated instrument reads above true. Nothing about the shape warns you, which is why the label matters more here than the size does.

What this cell can stand in for

1 designation Energizer no longer lists points at this cell as the closest thing it does list, and the voltage is the same. If a device was built for one of them, this is a straight substitution.

Every column of a row describes the discontinued cell it names. Fit reads that way too: it says whether that cell would enter this compartment, not whether this one enters its. Voltage is measured against this cell, the same way everywhere on the page: each row shows the discontinued cell’s own voltage and how far that voltage sits from this one.

What the chemistry changes

Everything above answers size and voltage. What it cannot answer is chemistry, and 3 other kinds are in play here beside the nickel-metal hydride this cell uses.

• Nickel-metal hydride is rechargeable and sits at 1.2 V, below the nominal of the primary cell whose slot it takes. It is never a drop-in for a primary cell no matter how well it fits, and a device that cuts off early will read it as flat.
• Alkaline drops in voltage steadily as it empties, so a device calibrated for a flat discharge will drift as it goes.
• Carbon zinc carries a fraction of the capacity of an alkaline cell of the same size and leaks more readily when spent.
• Lithium runs at 1.5 V, the same nominal the alkaline and silver classes carry. Of the 26 lithium cells here whose envelope the maker publishes, 3 share that envelope with an alkaline or silver cell.

Why this one is not a substitute for anything

HR03 is a rechargeable cell at 1.2 V, and no rechargeable cell is a drop-in for a primary one whatever the caliper says: the voltage is the objection, not the size. It measures the same as FR03, which runs 1.5 V against this cell's 1.2 V, +25.0%.

The gap is not the whole story. A nickel-metal hydride cell holds its voltage flat and then falls off a cliff, so a device that warns you before it dies will not warn you. Published capacity 500 mAh, and it is measured on a charge-discharge cycle, not on the shelf: this cell loses charge sitting in a drawer. The nearest is LR03: it drops straight in and runs 1.5 V, reads off.

• FR03, LR03 and R03 occupy the same envelope, 10.5 x 44.5 mm, and are the cells the compartment was drawn for.
• 5 cells measure close enough to compare against it in the Energizer data this site reads, and 5 of them are still listed.
• By stored energy it stands 3 of 4 in its envelope, at 600 milliwatt-hours.
• Energizer files it for Asia Pacific, Europe, Latin America and North America, which is where the part is sold rather than where the cell will work.

Drawn to scale

Every published figure

11 figures are published, and one is not: impedance. The row is absent rather than estimated. It reaches shelves as HR03-1000, HR03-850, NH12-500mAh and NH12-600mAh.

2 rows in the table are not the maker's but ours: stored energy and energy per cubic centimeter. Everything else is reproduced without change.

What the maker says about cold

The sheet for HR03 carries an operating range as well as a capacity, and it reaches 0 C (32 F) at the cold end. 4 more published figures follow it, and none of them reaches a cross-reference table.

The part occupies 3.8 cubic centimeters and weighs 12 g. Capacity and voltage together put 600 milliwatt-hours in that space. Energizer files it for Asia Pacific, Europe and Latin America.

Operating range

0 C (32 F) to 50 C (122 F). Below the lower figure the maker makes no claim at all, which is not the same as the cell stopping.

Cutoff voltage

1 V. The published capacity is counted down to this voltage; a device that quits higher up sees less than the whole figure.

Maker's classification

Rechargeable. That is the maker's own filing word for the part, not a standard designation.

Mass against volume

12 g filling 3.8 cubic centimeters. When the printing has worn off, a kitchen scale separates two cells of one envelope faster than a caliper does.

Where the part is filed

Asia Pacific, Europe, Latin America and North America. That is a statement about the maker's distribution and not about where the cell works.

Is that a lot of energy?

It ties. 1 other cell in this shell stores the same 600 milliwatt-hours, so they share place 3 of 4 instead of being put in an order the figures do not support. Per unit of volume that is 158 mWh per cubic centimeter, denser than 13% of everything measured here.

Less energy per cubic centimeter than most

HR03 carries less in its volume than most: 158 milliwatt-hours per cubic centimeter, below 87 percent of everything here that publishes both figures.

5 of those ones are still listed. Its 158 milliwatt-hours per cubic centimeter sit above 13 percent of everything here that publishes both a capacity and a volume. 5 of the 69 cylinders share its 1.2 V exactly.

• 3-312I — the next step down by volume: 3.6 cubic centimeters against this cell's 3.8.
• R03 — the next step up: 4 cubic centimeters, 105% of this one.
• 1.2H1 — 10.5 x 44.5 mm, 1.2 V, nickel-metal hydride.
• 1811A — 10.3 x 28.5 mm, 12 V, alkaline.

The maker's own part numbers

HR03 carries 8 names beyond the designation, and every one of them is a manufacturer part number: a catalog line, not a size and not a standard.

• 1.2H1 — a manufacturer part number for HR03, not a standard designation.
• NH12-500MAH — a manufacturer part number for HR03, not a standard designation.
• NH12-700MAH — a manufacturer part number for HR03, not a standard designation.
• The maker's own catalog carries 7 product lines under it.

The cell that differs only in depth

The code says the size, so the cells that get confused with HR03 are the ones that keep its diameter and change its depth. 5 cells share this diameter at depths from 15.5 to 43.3 mm, and every one of them enters the same opening.

It stands 3 of 4 in this envelope by stored energy. On a scale the difference shows before it shows on a caliper: this one weighs 12 g.

• E11A — same diameter, 15.5 mm tall against this cell's 44.5: 29 mm shallower, which neither designation carries.
• E11AZ — same diameter, 15.5 mm tall against this cell's 44.5: 29 mm shallower, which neither designation carries.
• 1811A — same diameter, 28.5 mm tall against this cell's 44.5: 16 mm shallower, which neither designation carries.
• FR03 — the same 10.5 x 44.5 mm in lithium at 1.5 V. Identical on a caliper, different in the circuit.
• LR03 — the same 10.5 x 44.5 mm in alkaline at 1.5 V. Identical on a caliper, different in the circuit.

What this page cannot tell you

2 of the 7 fields this site reads are empty for HR03: impedance and operating temperature. Everything computed from them is absent from this page rather than estimated.

The blanks are the same in all 7 records behind this designation, so they are the catalog's silence and not a merge losing a value. What is not missing is the envelope: 10.5 x 44.5 mm, published and checked against the designation itself.

• 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.
• No operating temperature — so this page cannot tell you whether the maker claims anything at all below freezing.

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, carbon zinc, lithium and nickel-metal hydride. Same hole, different insides, different discharge curve.

• 1.2H1 — 10.5 x 44.5 mm, 1.2 V
• FR03 — 10.5 x 44.5 mm, 1.5 V
• LR03 — 10.5 x 44.5 mm, 1.5 V
• R03 — 10.5 x 44.5 mm, 1.5 V
• E11A — 10.2 x 15.5 mm, 6 V
• E11AZ — 10.2 x 15.5 mm, 12 V
• 1811A — 10.3 x 28.5 mm, 12 V
• 3-312 — 10.3 x 42.8 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.

Records that disagree behind this page

HR03 is assembled from 7 catalog records, and they do not agree with each other on every field. Both sides are numbered below so the disagreement can be read rather than taken on trust.

1. [1] Energizer catalog record 300, listed as NH12-700mAh, active in the snapshot. Technical data sheet: nh12-700.pdf.
2. [2] Energizer catalog record 303, listed as NH12-800mAh, active in the snapshot. Technical data sheet: nh12-800.pdf.
3. [3] Energizer catalog record 319, listed as RE12-500, active in the snapshot. Technical data sheet: re12-500_ap.pdf.
4. [4] Energizer catalog record 1247, listed as HR03-850, obsolete in the snapshot. Technical data sheet: hr03-850_eu.pdf.
5. [5] Energizer catalog record 1249, listed as HR03-1000, obsolete in the snapshot. Technical data sheet: hr03-1000_eu.pdf.
6. [6] Energizer catalog record 3021, listed as NH12-500mAh, active in the snapshot. Technical data sheet: nh12_500gl0221.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/hr03/. It loads nothing from anywhere else. Paste this:

<iframe src="https://batterycross.com/embed/hr03/" width="100%" height="520" loading="lazy" title="HR03 replacements"></iframe>