State of charge and resting voltage
| Charge | Battery | Range in the charts | Per cell |
|---|---|---|---|
| 100 % | 41.75 V | 41.68–41.98 V | 4.18 V |
| 90 % | 40.65 V | 39.84–40.89 V | 4.06 V |
| 80 % | 39.81 V | 38.74–40.26 V | 3.98 V |
| 70 % | 39.22 V | 37.83–39.62 V | 3.92 V |
| 60 % | 38.58 V | 37.14–38.83 V | 3.86 V |
| 50 % | 38.01 V | 36.50–38.38 V | 3.80 V |
| 40 % | 37.78 V | 36.12–38.03 V | 3.78 V |
| 30 % | 37.64 V | 35.87–37.64 V | 3.76 V |
| 20 % | 37.18 V | 35.52–37.32 V | 3.72 V |
| 10 % | 36.71 V | 34.92–36.84 V | 3.67 V |
| 0 % | 33.50 V | 28.00–35.00 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 1.88 V, so read the percentages as approximate. Above about 40.65 V the battery is nearly full; below about 36.71 V little is left.
Charging and limits
| Charge (absorption) | 42.00 V (4.20 V max per cell) |
|---|---|
| Float | none: the charger stops when the current falls |
| Discharge cut-off | 25.00 V under load (cell datasheets) |
| Storage | 38.00–38.50 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) 18650 / 1S LiPo cell (3.7 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) 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 a 36 V Li-ion battery at 50 %?
About 38.01 V at rest; the charts we used range from 36.50 V to 38.38 V.
What voltage is a 36 V Li-ion battery at 100 %?
About 41.75 V at rest, hours after charging. While charging, the charger holds it at 42.00 V.
At what voltage is a 36 V Li-ion battery empty?
At rest, below about 36.71 V only about 10 % is left, and devices usually stop at about 33.50 V. Under load the cells are rated down to 25.00 V.
Sources: the makers’ charts and datasheets listed on the calculator page.