Abstract

Battery monitoring is used to acquire information about batteryconditions. It’s a regular technology which most of us use on daily bases.The charge gauge in a cellphone, consisting of bars which indicate the degreeof charge left in the battery is an example. Battery monitoring gives thecellphone user information about the battery. The background to this thesiswork is that this technology is requested for vehicles because empty orbroken batteries are one of the most common causes for involuntary stops. Oneway to monitor battery conditions is with a battery sensor, which is amechanical device that measures and calculates battery conditions. This thesis’ purpose is to develop evaluation criteria and evaluationmethods to assess the possibility for battery sensors to deliver competentinformation in order to ensure functionality of electric systems. To enablegeneralized evaluations of battery sensors, their delivered information aredelimited to three different and defined battery conditions which areState-Of-Charge (SOC), State-Of-Function (SOF) and State-Of-Health (SOH). To be able to compare battery sensor calculations and actual batteryconditions, a method to obtain the battery conditions was needed. Todetermine this method a literature review was done and because of an accurateand continuous method was needed Coulomb counting was selected. Coulombcounting is a book-keeping method which calculates the SOC accurate based oncurrent integration. To develop criteria which evaluate battery sensors possibilities to delivercompetent information, tests about how vehicles starting affect batteries aswell as tests about battery sensors performance in different scenarios havebeen investigated. This thesis work shows that the SOC has to be limitedbased on the degree of charge left in a battery, SOF has to be limited tobatteries potential to deliver a certain voltage for a specific constantcurrent and for SOH it is most important to maintain a continuous countdown. The evaluation methods to evaluate battery sensors according to the criteriahave been developed to test and ensure the battery sensors’ performancebased on several test-cycles. The evaluation methods with certain conditionsand test-cycles should be comparable to actual conditions for battery sensorsinstalled on vehicles to ensure a continuous delivering of competentinformation. To summary this thesis work has developed and partly verified evaluationcriteria and evaluation methods to evaluate battery sensors’ possibility todeliver competent information about the battery conditions SOC, SOF and SOH.These criteria and methods make it possible to evaluate if a battery sensor,any battery sensor calculating these battery conditions based on similarparameters, could deliver enough competent information in order to ensurefunctionality of electric systems.