10440 vs AAA
The 10440 is an AAA-sized 3.6 V lithium-ion cell. The AAA is 1.5 V alkaline. Same footprint, incompatible electrically.
A 10440 looks like an AAA and fits like an AAA, but it is a rechargeable lithium-ion cell at 3.6 volts where the AAA is alkaline at 1.5. More than double the voltage, in a cell that slides into the same slot. Fitting one in an ordinary AAA device can destroy it. Only use a 10440 in equipment that names it specifically.
- Verdict:
- AAA-shaped, 3.6 V — not a substitute
- Interchangeable:
- no
These fit the same space but are not electrically compatible
The 10440 runs at 3.6 V against the AAA’s 1.5 V — a 2.1 V difference between two cells that drop into the same compartment. Nothing about the fit stops you making this mistake, so check the code on the cell, not its shape. The AAA is also single-use: putting one in a charger built for the 10440 can make it vent, leak or catch fire.
Side-by-side specifications
| Specification | 10440 | AAA |
|---|---|---|
| Chemistry | Li-ion | Alkaline |
| Type | Cylindrical | Cylindrical |
| Nominal voltage | 3.6 V | 1.5 V |
| Diameter | 10 mm | 10.5 mm |
| Height | 44 mm | 44.5 mm |
| Typical capacity | 300–350 mAh | 850–1200 mAh |
| Rechargeable | Yes | No |
| Also sold as | ICR10440 | LR03, MN2400, AM4, R03 |
Size comparison
Near enough to interchange by hand — 10 × 44 mm against 10.5 × 44.5 mm — which is precisely why the voltage difference matters here.
Why the sizes match
10 mm across and 44 mm long, against 10.5 × 44.5 mm for an AAA. The numbering describes the dimensions, which is why Li-ion cells shadow the household sizes so closely.
The voltage gap
3.6 V nominal, up to about 4.2 V fully charged, against a flat 1.5 V. Very few devices built for an AAA tolerate that.
Small cell, real hazard
At 300–350 mAh the 10440 holds little energy, but lithium-ion cells this small still vent violently if over-discharged or charged on the wrong charger. Treat it as equipment, not as a household battery.
Can I use a AAA instead of a 10440?
No — and the fit will not stop you. The AAA measures 10.5 × 44.5 mm against 10 × 44 mm, close enough that it will sit in the same compartment. The problem is electrical: 3.6 V against 1.5 V. Fitting the 10440 where the AAA belongs feeds a device more than it was built for, which can damage it immediately or shorten its life. Match the code printed on the cell you removed.
Check before you swap. Batteries with similar dimensions are not always interchangeable. Always verify voltage, chemistry and the requirements printed in your device manual before fitting a replacement.