136 Chapter 11 ( Table 1 ), or ingress protection (IP), rating needs of the system. For automotive systems, it is most frequently desired to ensure that the system is sealed against both liquid and dust intrusion, which is known as IP6K9 rating. The IP rating code was developed as part of the International Electrotechnical Commission (IEC) standard 60529. The first digit represents the level of protection that the unit provides for dust and physical intrusion, in other words it protects against dust getting into the pack as well as protecting against getting things like fingers into your battery pack design.
The second character refers to the protection against liquid intrusion ranging from dripping liquids to full submersion and water spray (Maxim Integrated, 2007). Another type of enclosure rating that must be thought through is the National Electrical Manufacturers Association (NEMA) rating system ( Table 2 ). The NEMA rating system was set out for electrical equipment that is intended for installation in either indoor or outdoor systems. Therefore, it is more common to find in stationary and grid-type applications, both industrial and household. When it comes to NEMA-rated enclosures, there are many manu- facturers that currently produce standardized NEMA enclosures.
So for smaller ESSs, it is easier to purchase an off-the-shelf enclosure that already meets the NEMA standards. The NEMA and IEC IP standards are similar, but NEMA ratings and testing specify the degrees of protection against mechanical damage of equipment, risk of explosions, or conditions such as moisture (produced, for example, by condensation), corrosive vapors, fungus, and vermin as compared to the IEC IP which only indicates protection against dust and liquid intrusion (National Electrical Manufacturers Association, 2005). Table 1:
International protection classes Level Dust and object protection Level Liquid protection 0 No protection 0 No protection 1 Protection against body surface 1 Protection against dripping water touch 2 Protection against finger insertion 2 Protection against dripping water at 15° tilt from normal position 3 Protection against tools and thick 3 Protection against spraying water wires 4 Protection against small parts—wires 4 Protection against splashing water and screws 5 Dust ingress not entirely protected, 5 Protection against water jets at 30 kPa no contact 6 No ingress of dust, no contact 6 Protection against powerful water jets at 100 kPa 6K Protection against powerful water jets at 1000 kPa 7 Protection from immersion up to 1 m 8 Protection from immersion beyond 1 m 9K Protection against powerful high-temperature water jets