Index / Lithium-ion cells
18650 battery size and voltage, and the lithium-ion cells shaped like AA and CR123A
A 18650 battery is a rechargeable lithium-ion cylinder 18 mm across and 65 mm long, which is what its digits say. 18650 batteries of any brand are this one cell, whether the label says 18650 rechargeable batteries, 18650 lithium battery or 18650 li-ion battery. It is rated 3.6 V nominal and reads up to 4.2 V straight off the charger. Nothing in the Energizer catalog this site reads is that size, so no single-use cell of any chemistry stands in for it. The lithium-ion cells that do share a shape with a single-use cell are smaller ones, and those are the dangerous lookalikes: 14500 the size of AA, 10440 the size of AAA, 16340 the size of CR123A, RCR123A the size of CR123A and 15270 the size of CR2.
Updated · data retrieved 1 September 2026
Fit answers whether it enters the compartment. Voltage answers whether the circuit will notice. A cell that fits is not always a safe substitute.
| Lithium-ion cell | Size in the name | Nominal | Charged | Made in the shape of | In a device built for it |
|---|---|---|---|---|---|
| LIR2032 | 20 x 3.2 mm | 3.6 V | 4.2 V | CR2032 (20 x 3.2 mm, 3 V) | 3.6 V +20.0%, reads off; 4.2 V +40.0%, wrong class |
| LIR2025 | 20 x 2.5 mm | 3.6 V | 4.2 V | CR2025 (20 x 2.5 mm, 3 V) | 3.6 V +20.0%, reads off; 4.2 V +40.0%, wrong class |
| LIR2016 | 20 x 1.6 mm | 3.6 V | 4.2 V | CR2016 (20 x 1.6 mm, 3 V) | 3.6 V +20.0%, reads off; 4.2 V +40.0%, wrong class |
| LIR2450 | 24 x 5 mm | 3.6 V | 4.2 V | CR2450 (24.5 x 5 mm, 3 V) | 3.6 V +20.0%, reads off; 4.2 V +40.0%, wrong class |
| LIR1220 | 12 x 2 mm | 3.6 V | 4.2 V | CR1220 (12.5 x 2 mm, 3 V) | 3.6 V +20.0%, reads off; 4.2 V +40.0%, wrong class |
| 14500 | 14 x 50 mm | 3.6 V | 4.2 V | AA (14.5 x 50.5 mm, 1.5 V) | 3.6 V +140%, wrong class; 4.2 V +180%, wrong class |
| 10440 | 10 x 44 mm | 3.6 V | 4.2 V | AAA (10.5 x 44.5 mm, 1.5 V) | 3.6 V +140%, wrong class; 4.2 V +180%, wrong class |
| 16340 | 16 x 34 mm | 3.6 V | 4.2 V | CR123A (17 x 34.5 mm, 3 V) | 3.6 V +20.0%, reads off; 4.2 V +40.0%, wrong class |
| RCR123A | no size in the name | 3.6 V | 4.2 V | CR123A (17 x 34.5 mm, 3 V) | 3.6 V +20.0%, reads off; 4.2 V +40.0%, wrong class |
| 15270 | 15 x 27 mm | 3.6 V | 4.2 V | CR2 (15.6 x 27 mm, 3 V) | 3.6 V +20.0%, reads off; 4.2 V +40.0%, wrong class |
| 18650 | 18 x 65 mm | 3.6 V | 4.2 V | nothing in this data | — |
| 21700 | 21 x 70 mm | 3.6 V | 4.2 V | nothing in this data | — |
What size is a 18650 battery?
18 mm across and 65 mm long. An AA, by comparison, is 14.5 x 50.5 mm in the Energizer data (LR6), so a 18650 is wider and longer than an AA and goes only where a device was built for it.
What voltage is a 18650 battery?
3.6 V nominal and up to 4.2 V when fully charged, the figures every lithium-ion cell on this page shares. The nominal alone is 2.4 times the 1.5 V of an alkaline AA, which is why the smaller lithium-ion cells below must never go into a holder built for single-use cells.
Is a 21700 bigger than a 18650?
Yes. A 21700 battery is 21 mm across and 70 mm long, against 18 x 65 mm for a 18650, so it does not go into a holder made for a 18650. The voltage is the same, 3.6 V nominal.
Drawn to one scale
The AA from the Energizer data, and the lithium-ion cells drawn from the digits of their names. The digits are rounded to the millimeter across, so a given product can measure a few tenths more; the line marks the length of the AA.
Lithium-ion cells in the shape of a single-use cell
Each of these is sold to go where a single-use cell goes, and a device built for the single-use cell cannot tell them apart by fit. The percentage is the voltage of the lithium-ion cell against the cell the device was built for, the same figure the page of that cell prints in its lookalike section.
Is a 14500 the same as an AA battery?
The same shape, not the same battery: a 14500 battery is rechargeable lithium-ion at 3.6 V against the 1.5 V of LR6, and up to 4.2 V straight off the charger: a higher voltage class. The table above gives the difference in per cent. The name reads 14 x 50 mm; LR6 is 14.5 x 50.5 mm in the Energizer data.
Is a 10440 the same as an AAA battery?
The same shape, not the same battery: a 10440 battery is rechargeable lithium-ion at 3.6 V against the 1.5 V of LR03, and up to 4.2 V straight off the charger: a higher voltage class. The table above gives the difference in per cent. The name reads 10 x 44 mm; LR03 is 10.5 x 44.5 mm in the Energizer data.
Is a 16340 the same as a CR123A battery?
The same shape, not the same battery: a 16340 battery is rechargeable lithium-ion at 3.6 V against the 3 V of CR17345, and up to 4.2 V straight off the charger: a higher voltage class. The table above gives the difference in per cent. The name reads 16 x 34 mm; CR17345 is 17 x 34.5 mm in the Energizer data.
Is an RCR123A the same as a CR123A battery?
The same shape, not the same battery: an RCR123A battery is rechargeable lithium-ion at 3.6 V against the 3 V of CR17345, and up to 4.2 V straight off the charger: a higher voltage class. The table above gives the difference in per cent.
Is a 15270 the same as a CR2 battery?
The same shape, not the same battery: a 15270 battery is rechargeable lithium-ion at 3.6 V against the 3 V of CR2, and up to 4.2 V straight off the charger: a higher voltage class. The table above gives the difference in per cent. The name reads 15 x 27 mm; CR2 is 15.6 x 27 mm in the Energizer data.
Rechargeable lithium-ion coins
The same holds for coins. LIR2032, LIR2025, LIR2016, LIR2450 and LIR1220 are lithium-ion coins in the sizes of CR2032, CR2025, CR2016, CR2450 and CR1220; the code after LIR is the same size code a CR coin carries.
What this page does not know
Capacity, current rating, whether a cell has a protection circuit and how long that makes it: all of it differs by product and none of it is in the data this site reads, which is one manufacturer’s catalog of single-use and nickel-metal hydride cells. The sizes here are the sizes written into the names and the voltages are the nominal and charged figures for lithium-ion named in the sources below. A cell’s own data sheet overrides both.
When a lithium-ion cell is spent, the EPA’s rule for rechargeable batteries applies; it is quoted on the battery disposal page.
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 here is the figure for one swap: the voltage of the cell that goes in, measured against the cell the device was built for, and the figure belongs to the cell whose voltage is printed beside it. In the table of cells that fit in place of this one, and on the scale, that is each candidate against this cell: a cell that runs lower carries a minus, one that runs higher carries a plus, and a cell at the same nominal voltage carries zero. In the table of cells no longer made, it is this cell against each of them, because the swap goes into a device built for the old cell, and that cell’s own page prints the same figure for the same swap. Where cells still listed can each stand in for the other, those are different swaps: each page measures against its own cell, the sign is the other one, and the size can differ slightly, because one gap is a larger share of the lower voltage; 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.