Introduction 5 pack, the electronics for the control system, the thermal management of the cells, the elec- tronics and software that manage the system, and the mechanical and structural components of the battery. In other words, the single topic of Li-ion battery pack engineering involves almost every engineering field. One of the biggest challenges that many people have when thinking about batteries is that they have a tendency to treat batteries like they are commodities, parts, and components that are easily substitutable with similar parts from different manufacturers. Unfortunately, Li-ion batteries are more akin to critical core engineering systems such as engines or transmissions.
This commodity-based perspective leads to a narrow perspective for the planning, scope, and cost of the battery systems. This book will attempt to offer a view into the complexity of the battery system in order to help the reader understand why the battery is not a commodity in the automotive market today and is not likely to become one in the near future. This leads us to the second goal of this book which is to put these different subcomponents and their discussions into the perspective of the standard engineering design process.
One of the frequent challenges of engineering battery packs, especially for large and transportation- related applications, is that the timing related to these activities is not clearly understood. Many people will make comparisons to the portable power industry which uses about a 12- to 18-month-design cycle from concept to mass production for a product with a 2- to 3-year life. However, when we apply the repeating “Design, Build, Test” design process to automotive applications, it is generally a 2- to 3-year-process from concept to production.
This surprises many people, however, we must remember that the typical automotive design cycle can run up to 4 years or longer depending largely on the amount of validation and verification testing that is needed. There are several reasons for the long duration of timing, including long testing periods (a battery “life cycle” test typically runs for a year or longer), long production tooling times (some “hard” tooling can have lead times of 25–30 weeks or greater), and on top of these long lead time items. There are some “hard stops” in the process such as needing to complete testing before sourcing and achieving design freezes before beginning prototype sourcing.
Add to these, the need to complete, on average, two to three design cycles (usually timed to match a vehicle prototype build) and you end up with a 24- to 36-month-long battery pack design cycle. Of course that does not mean that there are not methods that can be used to reduce that timing largely depending on whether it is a production program, the final intended use, the lifetime performance duration, the existence of similar products, and the amount of risk that the company is willing to take. In a typical design project, all phases are completed in series, in other words one after another.
However, there are various reasons that you may be able to overlap some of the phases and run them in parallel in order to reduce the overall project timing.