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. To post a message to the list, send your e-mail to <emc-p...@ieee.org> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <emcp...@radiusnorth.net> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher: <j.bac...@ieee.org> David Heald: <dhe...@gmail.com>
