State of charge and resting voltage
| Charge | Battery | Range in the charts | Per cell |
|---|---|---|---|
| 100 % | 4.18 V | 4.17–4.20 V | 4.18 V |
| 90 % | 4.06 V | 3.98–4.09 V | 4.06 V |
| 80 % | 3.98 V | 3.87–4.03 V | 3.98 V |
| 70 % | 3.92 V | 3.78–3.96 V | 3.92 V |
| 60 % | 3.86 V | 3.71–3.88 V | 3.86 V |
| 50 % | 3.80 V | 3.65–3.84 V | 3.80 V |
| 40 % | 3.78 V | 3.61–3.80 V | 3.78 V |
| 30 % | 3.76 V | 3.59–3.76 V | 3.76 V |
| 20 % | 3.72 V | 3.55–3.73 V | 3.72 V |
| 10 % | 3.67 V | 3.49–3.68 V | 3.67 V |
| 0 % | 3.35 V | 2.80–3.50 V | 3.35 V |
Resting voltage at 20–25 °C. Typical: median of four measured tables (Samsung SDI, Libre Solar, PineNote, Anbernic); range: all four. Readings taken hours after the last charge or discharge.
What to know
Li-ion cells don’t all follow the same curve: in the middle of the range the tables we used differ by about 0.19 V, so read the percentages as approximate. Above about 4.06 V the battery is nearly full; below about 3.67 V little is left.
Charging and limits
| Charge (absorption) | 4.20 V maximum |
|---|---|
| Float | none: the charger stops when the current falls |
| Discharge cut-off | 2.50 V under load (cell datasheets) |
| Storage | 3.80–3.85 V |
| Charging temperature | 0–45 °C |
From the datasheets and manuals in the sources: the datasheet of your battery or charger comes first.
Tips
On a pack, also measure each cell at the balance plug: one weak cell can hide behind a normal total.
To store Li-ion and LiPo for weeks, leave them at about 3.8–3.85 V per cell (Grepow’s storage charge), neither full nor empty.
Measure at the battery terminals with everything disconnected. A meter that is off by a hundredth of a volt per cell already matters on LiFePO4 and Li-ion.
Open in the calculator →Enter the voltage you measured and get the charge with its range.
Other batteries
12 V LiFePO4 battery (4S) 24 V LiFePO4 battery (8S) 48 V LiFePO4 battery (16S) LiFePO4 cell (3.2 V) 2S Li-ion / LiPo (7.4 V) 3S Li-ion / LiPo (11.1 V) 4S Li-ion / LiPo (14.8 V) 6S LiPo (22.2 V) 36 V Li-ion battery (10S) 48 V Li-ion battery (13S) LiHV cell (4.35 V) 12 V AGM battery 12 V gel battery 12 V flooded lead-acid battery 6 V flooded lead-acid battery NiMH cell (1.2 V)
Frequently asked questions
What voltage is an 18650 or 1S LiPo cell at 50 %?
About 3.80 V at rest; the charts we used range from 3.65 V to 3.84 V.
What voltage is an 18650 or 1S LiPo cell at 100 %?
About 4.18 V at rest, hours after charging. While charging, the charger holds it at 4.20 V.
At what voltage is an 18650 or 1S LiPo cell empty?
At rest, below about 3.67 V only about 10 % is left, and devices usually stop at about 3.35 V. Under load the cells are rated down to 2.50 V.
Sources: the makers’ charts and datasheets listed on the calculator page.