Electronically Isolated Measuring Circuit for Multicell Traction Battery Modules Identifying State of Charge (SOC) Values

Abstract

Paper focuses on the topic related to State of Charge (SOC) estimation of the battery modules. The design issues of the electronic circuit suited for very accurate voltage and current measurement used for evaluation of the SOC parameters of battery module (NexSys 12 V) are presented. The SOC evaluation is not described here, but the principles are based on the open-circuit voltage measurement in combination with the coulomb counting method. Both methods are considered within the practical design of the measuring circuit of traction lead-acid batteries connected in series (3 cells). The circuit proposal is verified by the simulation model and consequently by the experimental measurement. Mutual comparisons are done for each battery within the module. The results show a very high accuracy between the simulation and measurement, while the relative tolerance varies from - 7 % to 1 % within wide measuring ranges.