Li-ion Battery Voltage Chart | State Of Charge At A Glance

Standard Li-ion cells read about 4.20V when full, roughly 3.75–3.82V at half charge, and near 3.00V when empty.

A lithium-ion cell’s voltage is the closest thing it has to a fuel gauge, and reading that number against a Li-ion battery voltage chart tells you roughly how much charge is left. For a standard 3.6V/3.7V cell, the useful span runs from about 4.20V at full charge down to roughly 3.00V at empty.

The “3.7V” printed on most cell labels is the nominal voltage — the midpoint of the working range, not the full or empty value. Full charge sits higher, and cutoff sits lower, which is why the chart below exists. It maps resting voltage to state of charge for the standard lithium-ion chemistry found in most phones, laptops, power tools, and portable power packs.

What Voltage Matches Each State Of Charge?

For a standard Li-ion cell, 4.20V means 100%, about 3.75–3.82V means roughly half, and 3.00V is essentially empty. The resting-voltage curve looks like this:

These values describe resting voltage for standard NMC/NCA cells and match published reference charts, including Adafruit’s Li-ion and LiPo voltage guide. Treat them as a guide: the same cell reads differently after charging, under load, or in extreme temperatures.

Notice how flat the middle of the curve is. Between roughly 70% and 30%, voltage only moves about 0.2V — that’s why a voltage chart is a rough gauge, not a precision fuel meter. The steep parts at both ends are where the cell signals “full” and “empty.”

How To Read A Multi-Cell Pack Voltage

For a multi-cell pack, convert pack voltage to a per-cell number by dividing by the number of series cells, then compare to the chart. A 3S pack at 11.10V, for instance, is 11.10 ÷ 3 = 3.70V per cell — roughly 40–50% charged. Most packs are labeled by nominal voltage: 14.8V means four 3.7V cells in series (4S), 22.2V means six (6S), and so on.

Full-charge pack voltages scale the same way: 1S is 4.20V, 2S is 8.40V, 3S is 12.60V, 4S is 16.80V, 7S is 29.40V, 10S is 42.00V, 13S is 54.60V, and 16S is 67.20V. The conversion works both directions: a 10S pack at 36.0V works out to 3.60V per cell — roughly 10%.

Measure at rest whenever you can. A cell that just left the charger carries surface charge that inflates the reading, and a cell under load reads lower than its true state of charge. Let the pack sit for a few minutes before judging it.

Multi-cell voltage is always a pack-level estimate — individual cells age and drift at different rates, so one weak cell can pull the whole pack down. A 14.8V pack is a 4S configuration; if you’re shopping that size, our roundup of the best 14.8V li-ion battery options sorts tested picks by capacity and build quality.

Why Chemistry And Charger Voltage Matter

The chart above applies only to standard 3.6V/3.7V cells. Newer 3.8V and 3.85V cells charge to 4.35V and 4.4V respectively, and lithium iron phosphate cells use a completely different curve.

Both the 3.6V and 3.7V labels describe the same standard Li-ion chemistry in practice and share the same 4.20V ceiling; the difference is largely a labeling convention.

Battery University’s BU-303 guide flags the confusion directly: the charger’s termination voltage must match the cell’s exact chemistry and nominal class. Charging a standard cell to 4.35V overstresses it, while stopping a high-voltage cell at 4.2V leaves capacity on the table. LiFePO4 makes the point even clearer — nominally 3.2V per cell with its own charge/discharge shape, so a standard Li-ion chart doesn’t apply.

Two hard limits protect any Li-ion cell: never charge past its rated maximum (4.20V for standard cells unless explicitly rated higher), and never deep-discharge below the manufacturer’s cutoff — published charts place the floor around 2.8V–3.0V per cell. Most devices and BMSs enforce both automatically; the risk appears when raw cells are handled outside a pack.

Finally, voltage is not capacity. The same 3.70V reading can mean more or less charge depending on load, temperature, and rest time. The reliable method stays short: identify the chemistry, let the cell rest, convert packs to per-cell voltage, and compare only against the matching chart — the table above covers the rest.

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