Spatially Resolved Measurements of Magnetic Fields Applied to Current Distribution Problems in Batteries

This paper presents a novel instrumentation system for spatially resolved measurements of steady-state and slowly time-varying magnetic fields. The instrumentation system has a measurement area of 400 mm × 200 mm consisting of 256 magnetic pixels each measuring the magnetic field crossing the center of the pixel area as three orthogonal vectors. The specified minimum resolution of our chosen sensor is approximately 1.0 × 10^-7 T and the maximum specified measurable magnetic field is 8.0 × 10^-4 T. Magnetic field data can be recorded at approximately one frame per second. This paper also reports the application of this instrumentation system to measurements on lead acid batteries and hybridized battery ultracapacitor combinations. The objective of this paper is to infer, for the first time, the moving charge distribution inside the battery volume by measuring the magnetic field resulting from the moving charge. Empirical tests are reported which show the current distribution as a function of increasing distance down the plate away from the terminal is highly likely to be exponential in nature, with most current flowing in the uppermost portion of the battery.