The systems engineering process is clearly defined for not only the department of defense, but for other government entities. Following this process is critical to the overall success of the program and DoD’s success to get a best value solution that is applicable to various platforms across multiple services. Ensuring that the requirements phase of the systems engineering process receives its due diligence will provide the design phase the critical details necessary to build a sub-system solution that will be easily integrated, across various platforms This paper will look at this process and show the importance of this process using a case study of the Military 6T start battery. In order to qualify a 6T Lithium Nanophosphate battery as a drop-in-replacement to 6T lead-acid batteries a requirement set and appropriate testing must be conducted. When it comes to battery chemistries Li-Ion chemistry is night and day compared to lead-acid chemistries. When developing a requirement specification for 6T Li-Ion battery it is important to consider omission of certain requirements from lead-acid specs and the addition of certain requirements relating to the specific chemistry and packaging requirements of Li-Ion batteries.