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Choosing a Cell Model

simses ships two built-in cell models. Both implement CellType and slot interchangeably into Battery. The table below is the quick chooser; each cell is then documented in its own section with source and a runnable snippet.

Comparison

Model Chemistry Format Nominal capacity Nominal voltage Voltage window Max C-rate (ch / dis) Rint model Default aging
SonyLFP LFP Cylindrical 26650 (26 × 65 mm) 3.0 Ah 3.2 V 2.0 – 3.6 V 1.0 / 6.6 2-D lookup in (SOC, T), separate charge/discharge curves Yes (Naumann)
Samsung94AhNMC NMC Prismatic (125 × 45 × 173 mm) 94.0 Ah 3.68 V 2.7 – 4.15 V 2.0 / 2.0 Constant 0.819 mΩ No

All values are per cell, taken directly from the model constructors.

SonyLFP

A small-format cylindrical LFP cell (Sony/Murata US26650FTC1) with a flat OCV plateau, strong cycle life, and a notably asymmetric C-rate (1.0 charge, 6.6 discharge). OCV, hysteresis, and the entropic coefficient are 1-D lookups in SOC; internal resistance is a 2-D lookup over (SOC, T) with separate charge and discharge tables. Ships a default degradation pair — Naumann 2018 calendar and Naumann 2020 cyclic — so multi-year stationary-storage runs with aging work out of the box.

Additional source: Naumann, M. Techno-economic evaluation of stationary lithium-ion energy storage systems with special consideration of aging. PhD Thesis, Technical University Munich, 2018.

from simses.battery import Battery
from simses.model.cell.sony_lfp import SonyLFP

battery = Battery(
    cell=SonyLFP(),
    circuit=(13, 1),
    initial_states={"start_soc": 0.5, "start_T": 25.0},
    degradation=True,                     # picks up the default Naumann pair
)

The degradation=True shortcut only works with cells that declare a default_degradation_model() — SonyLFP does. For warm-starting from a prior aging state, see Degradation.

Samsung94AhNMC

A large-format prismatic NMC cell typical of modern stationary-storage installations. 94 Ah is in the range used by grid-scale container systems where large-format prismatic cells dominate today. OCV is analytical — a sum of four sigmoid terms plus a linear term, steeper than LFP in the working range and useful for SOC estimation. Internal resistance is constant (0.819 mΩ); hysteresis and entropic coefficient are zero. No default degradation model ships with this cell — attach one explicitly, or run without aging.

Source: Collath, N., Tepe, B., Englberger, S., Jossen, A., Hesse, H. Suitability of late-life lithium-ion cells for battery energy storage systems, Journal of Energy Storage 87 (2024) 111508.

from simses.battery import Battery
from simses.model.cell.samsung94Ah_nmc import Samsung94AhNMC

battery = Battery(
    cell=Samsung94AhNMC(),
    circuit=(96, 1),
    initial_states={"start_soc": 0.5, "start_T": 25.0},
)

A 96-series string of these cells gives ≈ 353 V nominal with 94 Ah capacity — about 33 kWh of usable energy per string.

Extending

Writing a new cell model means subclassing CellType and implementing open_circuit_voltage() and internal_resistance(), plus (optionally) hysteresis_voltage(), entropic_coefficient(), and default_degradation_model(). See Extending Cell Models for the full walkthrough, including the test-harness hookup and the CSV-backed lookup pattern.

See Also