Battery Capacity Table (AA, CR2032, 18650…)
Typical capacity, voltage, and energy for common batteries from coin cells to 21700s, with a quick runtime estimator.
Typical battery capacities
Capacity is not a constant: it depends on load current, cut-off voltage, temperature, and manufacturer. Figures below are conservative typical values at light load — alkaline cells in particular deliver far less at high drain. Energy is computed as nominal voltage × capacity.
| Battery | Chemistry | Voltage | Typical mAh | Energy (Wh) | Rechargeable |
|---|---|---|---|---|---|
| CR2016 | Li coin | 3 V | 90 | 0.27 | no |
| CR2025 | Li coin | 3 V | 165 | 0.49 | no |
| CR2032 | Li coin | 3 V | 225 | 0.68 | no |
| AAA alkaline | Alkaline | 1.5 V | 1200 | 1.80 | no |
| AA alkaline | Alkaline | 1.5 V | 2500 | 3.75 | no |
| C alkaline | Alkaline | 1.5 V | 8000 | 12.00 | no |
| D alkaline | Alkaline | 1.5 V | 12000 | 18.00 | no |
| 9V alkaline (PP3) | Alkaline | 9 V | 550 | 4.95 | no |
| AAA NiMH | NiMH | 1.2 V | 800 | 0.96 | yes |
| AA NiMH | NiMH | 1.2 V | 2000 | 2.40 | yes |
| CR123A | Li primary | 3 V | 1500 | 4.50 | no |
| LS14250 (½AA LiSOCl₂) | LiSOCl₂ | 3.6 V | 1200 | 4.32 | no |
| ER14505 (AA LiSOCl₂) | LiSOCl₂ | 3.6 V | 2600 | 9.36 | no |
| ER26500 (C LiSOCl₂) | LiSOCl₂ | 3.6 V | 8500 | 30.60 | no |
| 14500 Li-ion | Li-ion | 3.7 V | 800 | 2.96 | yes |
| 18650 Li-ion | Li-ion | 3.7 V | 3000 | 11.10 | yes |
| 21700 Li-ion | Li-ion | 3.7 V | 5000 | 18.50 | yes |
Choosing by energy, not just mAh
mAh only compares batteries at the same voltage. A CR2032 (3 V, 225 mAh) holds about 0.68 Wh while an AA alkaline (1.5 V, 2500 mAh) holds ~3.8 Wh — the AA has eleven times the capacity in mAh terms but only five and a half times the energy. For electronics that boost or buck the rail, energy is the honest comparison.
Two IoT-specific notes: coin cells have high internal resistance, so radio bursts need a capacitor buffer to avoid brownouts; and LiSOCl₂ cells (ER14505 and friends) trade moderate capacity for a decade of shelf life and wide temperature range — that's why utility meters use them.
Related
Model a duty-cycled device with thebattery life calculator, and check the radio's contribution with thedata usage andlink budget calculators.
Common questions
- Will my device actually get the rated milliamp-hours?
- Usually not, and often not close. Capacity ratings are measured under gentle, standardised conditions — a low continuous drain at room temperature. Pull a burst of radio current from a coin cell, or run it at 0 °C, and internal resistance drags the terminal voltage below the cutoff long before the chemistry is exhausted. Treat the rating as a ceiling and design against a fraction of it.
- Why does a CR2032 die so quickly in a wireless device?
- Because its internal resistance is high — tens of ohms — so a transmit burst of 20 mA or more collapses the voltage momentarily. The cell recovers between bursts, but the device may already have browned out. The usual fix is a bulk capacitor across the cell to supply the peak, letting the cell provide only the average. Its 200-odd mAh is fine for a low duty cycle and hopeless for a chatty one.
- How do I turn milliamp-hours into runtime?
- Divide capacity by average current: 2,000 mAh at 1 mA average is nominally 2,000 hours. The word doing the work is average — for a duty-cycled device you must weight the sleep and active currents by how long each lasts, and sleep almost always dominates. The battery life calculator does that weighting for you.
- Is a higher-capacity cell always the better choice?
- Not necessarily. Capacity is only one axis; internal resistance, self-discharge, temperature range and voltage curve often matter more. A lithium primary cell holds its voltage nearly flat then drops off a cliff, which makes a fuel gauge useless but keeps a radio happy. An alkaline sags steadily, which is easy to measure but may fall below your regulator's dropout while plenty of energy remains.