Why does the battery model error increase significantly, in this case by more than four times, at lower temperatures? The pictured model validation shows drive cycle data unseen during model training

🔌 Increased Overvoltage: The overvoltage becomes much higher due to increased resistance. Since the ECM predicts the overvoltage, this results in a similar relative error against a much larger target.

🔄 Non-linear Effects: Non-linear effects become more pronounced, deviating from the linear ECM model structure. This increased non-linearity makes it more challenging to create a robust model that covers both high and low currents.

📉 Solid-phase Diffusion: Solid-phase diffusion becomes more restrictive, particularly at high currents. Traditional RC elements either poorly approximate this or fail to approximate it entirely.

🌡️ Temperature Rise: High resistance at low temperatures leads to significant heat generation, causing the cell's core temperature to rise above the Peltier-controlled surface temperature.

At About:Energy, we build models designed to generalise across a variety of operating conditions and establish best practices in parameterisation, allowing us to achieve high model accuracy within weeks.