46 Chapter 4 requirement document. You may also find that you can optimize a system to meet a custom- er’s specific key requirement. For instance, I have frequently found that it is possible to reduce the overall capacity of a battery pack by using a higher power cell for an application that really needs a power battery. In this type of case you may be able to offer a lower cost system to the customer that still meets their key requirements. Another key part of the requirements that you may not actually get in the requirement docu- ment but will be able to get while speaking to the customer is a performance profile.
In this case what you are looking for is the charging and discharging power and energy needs over a specified time period. Figure 6 below offers an example of this type of power profile; in this example we are looking at the power in Watts that is needed for an application over a 24-h time period. In this example the requirement may indicate that we need nearly 350 W of peak power, but in reviewing the operating profile we see that the application really only needs this much power for one short period each day and the average power demand is only 175 W.
That means that we may be able to offer them a slightly smaller capacity battery, but using a higher power cell we can still meet these peak power needs. At the other end of the requirements spectrum there are some requirements which may only tell you how much power or energy they need and not much more. For example I have seen some stationary and grid type battery requirements that only state that the system will need to deliver 15 MW of power for 15 min, for example.
In many of these types of requirement documents it is impossible to fully develop a battery proposal based solely on this limited WŽǁĞƌĞŵĂŶĚ;tͿdžĂŵƉůĞŽǀĞƌϮϰͲŚŽƵƌƉĞƌŝŽĚ ϰϬϬ ϯϱϬ ϯϬϬ ϮϱϬ ϮϬϬ ϭϱϬ ϭϬϬ ϱϬ Ϭ Ϭ ϭ Ϯ ϯ ϰ ϱ ϲ ϳ ϴ ϵ ϭϬ ϭϭ ϭϮ ϭϯ ϭϰ ϭϱ ϭϲ ϭϳ ϭϴ ϭϵ ϮϬ Ϯϭ ϮϮ Ϯϯ Ϯϰ WŽǁĞƌĞŵĂŶĚ;tͿ ǀĞƌĂŐĞWŽǁĞƌĞŵĂŶĚ;tͿ Figure 6 Sample power demand profile.