Reference chart

Battery voltage and capacity chart

A battery's label gives its nominal voltage, but a fresh one reads higher and a flat one lower. This chart gives the full, nominal and empty voltages of the common batteries, their typical capacity, and how full a lithium cell is from its voltage.

Voltages

Nominal is the label's voltage, about the average over a discharge. Full is a fresh or just-charged battery at rest, and empty is about where it's used up.

Battery	Nominal	Full	Empty
AA or AAA alkaline	1.5 V	1.6 V	about 1.0 V
AA or AAA NiMH	1.2 V	1.4 V	1.0 V
9 V alkaline	9 V	9.5 V	about 6 V
CR2032 lithium coin cell	3 V	about 3.2 V	2.0 V
18650 lithium-ion	3.6–3.7 V	4.2 V	2.5–3.0 V
LiPo cell	3.7 V	4.2 V	3.0 V
LiFePO4 cell	3.2 V	3.6 V	2.5 V

A pack multiplies these by the cells in series: a 2S LiPo is 7.4 V nominal and 8.4 V full, and four AAs make 6 V.

Capacity

Capacities vary by brand and by how hard you pull. These are typical figures at a gentle current:

Battery	Typical capacity	Rechargeable?	Good for
AA alkaline	2000–3000 mAh	No	Remotes, clocks, torches
AAA alkaline	1000–1200 mAh	No	Remotes, small gadgets
AA NiMH	1900–2500 mAh	Yes	Cameras, game controllers, torches
AAA NiMH	700–1000 mAh	Yes	Cordless phones, remotes
9 V alkaline	400–600 mAh	No	Smoke alarms, multimeters
CR2032	220–240 mAh	No	Watches, key fobs, tiny currents only
18650 lithium-ion	2000–3500 mAh	Yes	Power banks, torches, laptop packs
LiPo cell	Depends on size	Yes	Drones, phones, wearables

Alkaline cells give far less at high current: an AA that runs a clock for a year may last only an hour or two in a motor. A CR2032 is happiest at a few milliamps or less.

Lithium-ion state of charge

A lithium cell's voltage tells you roughly how full it is. Measure it at rest, after a few minutes with no load and no charger: a load pulls the voltage down and a charger pushes it up.

Charge	Resting voltage
100%	4.20 V
90%	about 4.11 V
80%	about 4.02 V
70%	about 3.95 V
60%	about 3.87 V
50%	about 3.84 V
40%	about 3.80 V
30%	about 3.77 V
20%	about 3.73 V
10%	about 3.69 V
0%	3.0–3.3 V: stop here

The figures vary from cell to cell and with temperature, so treat them as a guide. Notice how flat the middle is: from 60% down to 20% the voltage falls only about 0.15 V. For storage, leave a lithium cell at about 3.8 V, roughly half full.

Using the chart

Runtime: divide the capacity by the current. A 2000 mAh cell running a 100 mA load lasts about 20 hours; plan on 70–80% of that.
Compare in watt-hours: multiply amp-hours by the nominal voltage. A 3000 mAh, 3.7 V cell holds about 11 Wh; a 2500 mAh, 1.2 V AA holds 3 Wh.
Match cells: in series or parallel, use the same type, age and charge.

Free lesson

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Work it out

Battery life calculatorHours from mAh and milliamps, for a steady load or a device that sleeps.

The ideas behind it

Questions people ask

What voltage is a dead AA battery?

An alkaline AA starts at about 1.6 V and is close to flat by about 1.0 V under a load. A clock may keep running a little lower; a motor or a camera gives up sooner.

Can I use NiMH rechargeables instead of alkaline AAs?

Usually, yes. NiMH cells are 1.2 V against alkaline's 1.5 V, but an alkaline cell spends much of its life below 1.2 V anyway, so most devices run fine. Four NiMH cells make 4.8 V instead of 6 V, which only matters to a device that needs the full voltage.

What voltage is a fully charged 18650 or LiPo cell?

4.2 V for standard lithium-ion and LiPo cells, which are 3.6 or 3.7 V nominal. A few high-voltage cells charge to 4.35 V: only charge that high if the cell's datasheet says so.

How can I tell how full a lithium battery is?

Let it rest for a few minutes with no load and no charger, then measure it. About 3.85 V is half full, and below about 3.7 V there's little left. The voltage is flat through the middle, so a small change there means a lot of charge.