The applicable standards for lithium batteries depend on the application. I'm not that familiar with requirements for lithium batteries for aircraft systems, but that seems to be a new area. Apparently, the FAA wasn't aware enough of the issues when certifying the battery system for the 787 Dreamliner.
For commercial products, you have IEEE 1625, IEEE 1725, UL 1642, UL 2054, IEC 62133 and UN 38.3 which all require multiple redundant protective circuits. The protective circuit module (PCM) needs to use fuses, thermistors and other basic measures to provide the necessary protection. The purpose of the PCM is to protect the cells from faults in the charging circuit as well as from other potential hazards, such as short circuits, overloads and charging at high ambient temperatures. I can't state with certainty that immunity isn't an issue, but it isn't the likely issue. When testing PCMs, the assumption is that the charging circuit is one of the more likely places for faults to occur and the charging circuit is assumed to be unreliable. The effort is placed on designing the PCM to protect against such faults, and designing the cells to be robust enough to survive the faults. The problems with lithium cells are based on the efforts to get the maximum energy density. The insulators and separators within the cells are made as thin as possible. Manufacturing defects and contaminants can result in a puncture in a separator leading to an internal short circuit. This leads to a thermal event which can degrade other separators until they fail, cascading into a runaway event. If you look through the NTSB's preliminary reports, you will see that they are looking at such a fault as a likely cause of the event at Boston's Logan airport. http://www.ntsb.gov/investigations/2013/boeing_787/docket_documents.html Most designers of systems with lithium cells have no control over the power supply. The vast majority of devices with lithium cells are laptop computers, MP3 players, cell phone and such. The manufacturer may provide a power supply, but the manufacturer is also well aware that the customer may use an aftermarket supply. For USB charged devices, you have no idea what is providing the 5 VDC power. If low frequency noise from the switch-mode supply was an issue, I expect we would have seen more events during charging. Regards, Ted Eckert Compliance Engineer Microsoft Corporation ted.eck...@microsoft.com<mailto:ted.eck...@microsoft.com> The opinions expressed are my own and do not necessarily reflect those of my employer. From: Ed Price [mailto:edpr...@cox.net] Sent: Saturday, March 09, 2013 5:24 AM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: Immunity and emissions below 150 kHz and lithium batteries Another thing to remember is that the equipment in an aircraft isn't just randomly dumped into a compartment. Although 461 & 160 offer you a way to reasonably guarantee compatibility, it is with the assumption of good aircraft engineering practices. If you want to be able to mount the battery right on top of the charger, it is incumbent on YOU to verify that this is electronically, physically, thermally, chemically and magnetically safe. As to whether we should test anything for conducted susceptibility, well, both 461 and 160 already do that; Methods CS101 and CS114 are examples. And 9 kHz is just another arbitrary point, Method RE101 has you measuring magnetic field emissions starting at 30 Hz. To get a bit philosophical, the purpose of 461 and 160 was never to evaluate a device's compliance with those standards, but to ensure compatibility in real-life applications. So, if you are confronted with a gadget that just might do weird and nasty things when exposed to something not quite covered in the standard test suite, then it's your job to create an extension or customization of the testing program that will document (and regulate, mitigate or eliminate) those conditions. Ed Price WB6WSN Chula Vista, CA USA From: Ken Javor [mailto:ken.ja...@emccompliance.com] Sent: Friday, March 08, 2013 7:43 PM To: EMC-PSTC@LISTSERV.IEEE.ORG<mailto:EMC-PSTC@LISTSERV.IEEE.ORG> Subject: Re: [PSES] Immunity and emissions below 150 kHz and lithium batteries One thing that needs to be considered is RTCA/DO-160 section 20 conducted susceptibility requirements. I don't know into what category these lithium ion batteries fall, but given the consequences of failure, the military hits them with 200 V/m. I would be surprised if the commercial air community treated them significantly differently. The point being, there would be significant levels of conducted rf injected into the battery input terminals. At 200 V/m, the injected level would be 6 mA, 60 mA at 100 Hz, and 300 mA at 500 kHz and above. Ken Javor Phone: (256) 650-5261 ________________________________ From: Bill Owsley <wdows...@yahoo.com<mailto:wdows...@yahoo.com>> Reply-To: Bill Owsley <wdows...@yahoo.com<mailto:wdows...@yahoo.com>> Date: Fri, 8 Mar 2013 18:37:47 -0800 (PST) To: "EMC-PSTC@LISTSERV.IEEE.ORG<mailto:EMC-PSTC@LISTSERV.IEEE.ORG>" <EMC-PSTC@LISTSERV.IEEE.ORG<mailto:EMC-PSTC@LISTSERV.IEEE.ORG>> Subject: Immunity and emissions below 150 kHz and lithium batteries Recently, I heard of a couple of events, lithium battery fires it seems. Details are very nebulous for liability reasons. You know that part of the story. So I'm pondering as to what could have caused such an event. Since I get to measure radiated emissions down to 9kHz, I am aware of what there is in this realm. Back to the opening line... Lithium batteries are charged, in general, by switching power supplies. These switchng supplies run at a variety of frequencies, some well below 150 kHz. Now suppose you set a lithium battery powered device while being charged on top of or near to a device that operates at a frequency below 150 kHz. And suppose that the two operating frequencies are not liking each other... interference. One meets the emissions regulations and the other is not tested for immnity to those emissions below 150 kHz. Suppose the legal emissions interfere with the lithium battery charging circuit at frequencies below the immunity requirements... And some sort of unplanned for 'over charging' event happens and the lthium battery goes into a fault. We know which one that is. I suspect that the events I've heard of may have been due to such an interference with a laptop computers charging circuit and thus a subsequent battery fire. Could the airline battery fires be due to a low frequency interference with the charging circuit and thus caused an over charging event? Anyone have an abundance of laptops and a fireproof chamber to set up a large sample for testing? Out of 10's of thousands of units, only two have come to be noticed. But given the recent airline incidents and the absolute critical safety aspect of such an event... Much like the runaway electronic throttle, what is really happening ??? The events I heard of are barely safety related, having occurred in well protected space. So given the volitility of lithium battery fires, should we be testing the charging circuits to frequencies well below 150 kHz? Frequencies that could interfere with the feedback loop and cause over charging? with consequences... - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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