Thermodynamic testing of nickel metal hydride batteries

Nickel metal hydride (Ni-MH) batteries can be exothermic in both charge and discharge operating regimes. When considering Ni-MH batteries for application in severe operating environments, such as those requiring high-current, rapid discharge operations, the battery temperature is the limiting factor. Battery temperature control during charging can be accomplished by utilizing proper charging algorithms and/or charging systems that incorporate temperature measurement as a control factor. However, during discharge in severe operating conditions where limiting current draw in not possible, a temperature control system must be developed. For electric and hybrid vehicle applications, the temperature control system must have operating characteristics including lightweight and little or no power consumption required. To fully evaluate Ni-MH batteries in high-current discharge operating regimes, researchers at IUPUI first modeled the battery using Inertia(R), a finite element analysis (FEA) software package. Using the FEA results as a basis, a temperature control strategy was developed and a battery pack cooling system designed. As a validation method of the FEA model, bench testing of Ni-MH modules was conducted. This paper reports on the FEA modeling along with the results of the bench testing of the batteries in this severe operating regime.