In this guide, we'll take a detailed look at each stage of the battery pack assembly process, from battery pack design to delivery, exploring best practices that go into creating high-quality, safe, and efficient battery packs. Custom Battery Pack. The charging and discharging of lithium-ion batteries is a process of mutual conversion between electrical energy and chemical energy. In fact, it is the most time-consuming, accounting for about 40% of the total production time. Volumetric energy density has increased threefold while production costs have decreased by a factor of ten.