Cell data definitions

Ten terms, in Batemo's own words.

Capacity

The nominal capacity originates from the manufacturer's data sheet, if available. When the data sheet is unavailable, the nominal capacity is estimated. Batemo measured the C/10 capacity by discharging the cell at an ambient temperature of 25°C from 100% with a constant current of 0.1C until reaching the cell's lower voltage limit. The thermal boundary condition is free convection.

Continuous current

All quantities are measurement results from the Batemo battery laboratory. The continuous current is the highest current that completely discharges the cell without overheating it. Therefore, the cell is discharged from 100% state of charge (SOC) at an ambient temperature of 25°C with a constant current until a residual state of charge of 10% and either the cell's lower voltage limit or 90% of its maximum surface temperature is reached. The thermal boundary condition is free convection.

Peak current

The peak current is the current the cell can supply for 5 minutes. The cell is therefore discharged from 100% SOC at an ambient temperature of 25°C with a constant current until it reaches either the cell's lower voltage limit or its maximum surface temperature after 5 minutes. For cells that reach the maximum surface temperature, the measured current is taken directly as the peak current. For cells that do not reach the maximum surface temperature after 5 minutes because they reach the lower voltage limit first, the measured current is multiplied by a correction factor that estimates the current that would have heated the cell to the maximum surface temperature within 5 minutes. The thermal boundary condition is free convection. These operating conditions may be outside the cell manufacturer's specification.

Energy

Batemo measured the C/10 energy by discharging the cell at an ambient temperature of 25°C from 100% with a constant current of 0.1C until reaching the cell's lower voltage limit. The thermal boundary condition is free convection.

Mean voltage (C/10)

Batemo measured the mean voltage by dividing the C/10 energy by the charge the cell delivered during the same C/10 discharge. It is therefore the charge-averaged discharge voltage at an ambient temperature of 25°C, from 100% down to the cell's lower voltage limit, with free convection as the thermal boundary condition. It is a measured value, not a nominal voltage taken from the manufacturer's data sheet.

Power, continuous and peak

All quantities are measurement results from the Batemo battery laboratory. The continuous power is the highest power that completely discharges the cell without overheating it. Therefore, the cell is discharged from 100% state of charge (SOC) at an ambient temperature of 25°C with a constant current until a residual state of charge of 10% and either the cell's lower voltage limit or 90% of its maximum surface temperature is reached. The peak power is the power the cell can supply for 5 minutes. The cell is therefore discharged from 100% SOC at an ambient temperature of 25°C with a constant current until it reaches either the cell's lower voltage limit or its maximum surface temperature after 5 minutes. For cells that reach the maximum temperature limit, the measured power is directly taken as peak power. For cells that do not reach the maximum surface temperature after 5 minutes because they reach the lower voltage limit first, the measured power is multiplied by a correction factor that estimates the power that would have heated the cell to the maximum surface temperature within 5 minutes. The thermal boundary condition is free convection. These operating conditions may be outside the cell manufacturer's specification.

Energy density, specific and volumetric

The energy densities result from the C/10 energy, the cell weight and the cell volume.

Power density, specific and volumetric

The power densities result from the peak power, the cell weight and the cell volume.

Dimensions, mass and volume

Measured on the physical cell at Batemo, in Karlsruhe, Germany — not taken from the manufacturer's drawing. Volume is derived from the measured capacity and its volumetric density, not measured with a caliper.

Constant-current tests

The cell is discharged from 100% SOC or charged from 0% SOC with different constant currents at different ambient temperatures. The thermal boundary condition is free convection. The measurement stops when reaching either the cell's lower or upper voltage limit or its maximum surface temperature.

Pulse-current tests

The cell is discharged from 100% SOC or charged from 0% SOC with current pulses followed by no-load phases at different ambient temperatures. The thermal boundary condition is free convection. The measurement stops when reaching either the cell's lower or upper voltage limit or its maximum surface temperature.

Power-profile tests

The cell delivers a typical power profile from 100% SOC at different ambient temperatures. The thermal boundary condition is free convection. The measurement stops when reaching either the cell's lower voltage limit or its maximum surface temperature.

These definitions describe the measurement, not any one cell's result — the values themselves are on each cell's own page, measured on Batemo's own test benches in Karlsruhe, not taken from a manufacturer's data sheet.