36 Chapter 4 monitor (VTM) board. In addition to these there will be a thermal management system, which may range from a passive solution such as using the enclosure as a thermal heat sync to an actively managed liquid- or air-cooled system that forces cooled (or heated) air or liquid through the battery pack. And of course let us not forget the electronics, switches to turn the current flow on and off and wiring. All of these different systems must come together into a single system solution in order for the battery to be functional, safe, and meet its life and performance targets.
And while I will not spend much time trying to give cost or price estimates as there are many others out there who have continuous research on this aspect, I will offer up some thoughts as to what percentage of the battery these components make up. Note that for small power-based battery packs the cells make up much smaller percentage of the total pack cost, than compared to an electrical vehicle (EV) or a plug-in hybrid electrical vehicle (PHEV). This is also true of very large grid scale type systems, where the hard- ware around the cells may make up a larger percentage of the overall cost.
In the PHEV/ EV applications batteries can make up 60–70% of the complete battery pack costs ( Figures 2 and 3 ). Now that we have a basic understanding of the parts of the system, the next thing to under- stand when sizing a battery is what type of application it is? A battery is basically an electro- chemical energy storage device. And we can divide battery usage into two categories: either power or energy. A power battery can be described as one that is focused on providing “instant” power for vehicle acceleration. The power battery is not intended to provide long- term energy to operate a system.
Think of a power battery as one that discharges its power and energy in very small time frames, usually from seconds to tens of minutes. The energy battery is intended to provide a long and relatively slow discharge. Think of it as one designed to discharge its energy over 1 h or longer. In an automotive application this would typically be W,sͬs ϱй ϱй ĞůůƐ D^ ϭϬй ,ŽƵƐŝŶŐ ϭϬй tŝƌŝŶŐ KƚŚĞƌ ϳϬй Figure 2 PHEV/EV battery cost breakdown. BMS, battery management system.