PowerSource

There was an announcement yesterday from the Portable Rechargable Battery Association (PRBA) that they were successful in influencing the United Nations Subcommittee of Experts on the Transport of Dangerous Goods to modify the international testing requirements for large-format rechargeable lithium cells and batteries. According to the PRBA, the UN regulations were written in 2000 when the only practical lithium batteries were the small cells used in consumer electronics, and hybrid cars used lead acid or the really cool ones used NiMH. Also according to the PRBA, holding today’s state-of-the-art hybrid cars to the UN regulations would add about $500,000 to the cost of developing a battery pack.

Large format here means more than 500 g of lithium or more than 6200 Wh. For comparison, the Chevy Volt is reported to have a 16 kWh battery pack.

So I had two questions here, with the first being, what does the UN have to do with testing lithium ion batteries? I‘m familiar with test regulations from the IEEE, UL, and the IEC, but to me the UN is where you go to for investigating human rights violations, not electronics technology standards.

George A. Kerchner, the executive director of the PRBA, set me straight: UN Model Regulations cover the transport of dangerous goods (hazardous materials) and is coordinated by the Economic and Social Council (ECOSOC) Committee of Experts on the Transport of Dangerous Goods, which produces the "Recommendations on the Transport of Dangerous Goods Model Regulations." 

The US government, for example, incorporates these regulations into its hazardous materials regulations, and they are also used by international organizations such as the International Maritime Organization for for anything shipped by boat and the International Civil Aviation Organization, for anything shipped by planes. So updating the UN regulations for large format batteries is a big deal for companies developing lithium ion battery packs for hybrid cars.

Second questions: What’s changed in the regulations? The PRBA proposal adopted by the UN applies to testing requirements for discharged lithium ion cells and batteries. The UN subcommittee agreed it wasn’t necessary to test cells and batteries in the discharged state when the tests already require testing at 50% or 100% state of charge.

The PRBA also has a second proposal before the subcommittee that addresses the difference in battery pack architecture found in large format packs: In Kercher’s words, “Large format lithium batteries are constructed from many lithium cells. These cells are typically electrically connected together to form what is commonly referred to as a “battery module.” Modules are then electrically connected together to form a “battery assembly.” Cells used to construct modules are subject to UN testing requirements. Modules, because they meet the definition of a “battery” also are subject to UN testing requirements. With increasing size, battery manufacturers face dramatically increasing costs and testing complexities and considering assemblies comprise UN tested cells and modules, the benefits of such extensive testing of assemblies is of questionable benefit.”

You can read the PRBA proposals here.

On a side note, Tesla Motors announced a year ago that their cells met UN testing requirements, but the announcement only covered testing at the cell level.