from chemistry to pack
For most simple peak power calculations we will be interested in the Direct Current Internal Resistance (DCIR) value for a new cell at 50% SOC (25°C, 10s), Open Circuit Voltage (OCV) and minimum voltage. Note: this is just an estimation and this needs to be compared to the manufacturers specifications and tested values. However, as … Read more
The Galvanostatic Intermittent Titration Technique or GITT as most know it in the world of battery chemistry and modelling as it is used to estimate diffusion coefficients, OCV, over-potentials and resistance. First described by Weppner and R. A. Huggins [5]. The GITT measures the transient voltage change and open circuit voltage (OCV) change during the charging … Read more
Knowing the power demand for a battery cell or pack is really useful, but how do you turn that into a current demand? The following image shows the solution we use in the Battery Calculations Workbook and in the Vehicle Model. At first it can look daunting, but it is quite simple, maybe too simple … Read more
Authors: Marcus Tuchel, Prof. Emma Kendrick School of Metallurgy and Materials, University of Birmingham, Elms Rd, Birmingham B15 2SE Abstract Methodology Extrapolated OCV Li ion diffusion coefficient Conclusions and Future Work References Research Bio Marcus Tuchel is a PhD student in the Birmingham Energy Materials Group, under the supervision of Prof. Emma Kendrick and Prof. … Read more
The measurement of Open Circuit Voltage can be time consuming as it needs to be established versus the State of Charge (SoC) of the cell. Doing this in fine steps from 0% to 100%, with the measurement being made “at rest”, means we have to charge/discharge and then let it rest before making the voltage measurement. The … Read more
It is really important to understand the sources of error with the coulomb counting method as this forms the backbone for most SOC estimation algorithms. SoC Estimation by Coulomb Counting is based on the measurement of the current and integration of that current over time. There are five main sources of error with the coulomb … Read more